Jaguar XK8 - ZF6HP26 Transmission - Critical Intel!
#21
12-14-2018, 06:43 PM
Hi Bernie, a very interesting post. I have a 2003 S-type 4.2l with the same ZF6HP26 trans. It always seems to be labouring when shifting from 4 to 5th and 5th to 6th even when warmed up. I have also spent thousands trying to get rid of the "surge" when its cold and sitting at low constant speeds (around 60km/h). This is the first time I have read that it might be a wheel bearing issue. I had the software update and it did nothing and was considering getting the torque converter worked on (that would be big dollars!). Mine is not throwing up any faults but I might follow your advice and have the bearings checked first. When I do I will post the results... Cheers... Dave 
#22
12-28-2018, 06:28 PM
Hi Bernie, a very interesting post. I have a 2003 S-type 4.2l with the same ZF6HP26 trans. It always seems to be labouring when shifting from 4 to 5th and 5th to 6th even when warmed up. I have also spent thousands trying to get rid of the "surge" when its cold and sitting at low constant speeds (around 60km/h). This is the first time I have read that it might be a wheel bearing issue. I had the software update and it did nothing and was considering getting the torque converter worked on (that would be big dollars!). Mine is not throwing up any faults but I might follow your advice and have the bearings checked first. When I do I will post the results... Cheers... Dave
Your symptoms do not sound the same as mine so I am not sure it is the same problem but what the hell, only takes about 5 minutes per wheel to check it.
Yes, p[lease let the thread know if it is something you might be investigating further
#23
12-28-2018, 06:32 PM
So I just went ahead and did what I know to do . I removed the rear hubs from the car, hammered out the old bearings with a drift and 4lb sledge and using my trusty Harbor Freight press, pushed in a fresh set of bearings into each hub.
Getting out one of the old ones was a bear but only because the bearing was failing badly
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JimmyL (12-29-2018)
#24
01-05-2019, 12:42 PM
Hi guys, I'm a newbie here - in fact this is my very first ever post so I'll probably screw this up, it's just that it's so recent I thought I'd chime in - but I've been following this and it's (razorboy's) preceding post(s) with interest. I have an '04 XKR conv. I picked up 1 1/2 years ago and I'm loving it. I have zero issues so far and want to keep it that way. The car only had 39,000 miles when I got it and about 58,000 now so the only thing I'm worried about is that I'm running the wheels off it! I'm planning a trans fluid change at around 60,000 so we'll see how that goes. The main reason I'm posting is the only incident I've had so far is a few months ago when the ABS fault light suddenly came on out of the blue only about 1/2 mile from home. So after getting home while trying to see if this stupid "Blue Driver" diagnostic/smart phone do-all tool would tell me anything (which it would not, doesn't appear to have ABS though it otherwise did interface with the Jag to some degree) the light went out and I've had no problems since. Does anyone think that 58,000 miles is too soon to be having wheel bearing issues?
Razorboy, when the time does come, I take it changing wheel bearings is no big deal? How big a HF press do you have?
This is a great forum and I'm trying to take in the wealth of information on here from so many great people! Kudo's to all and keep the info coming...I'm only having a hard time getting enough!
Razorboy, when the time does come, I take it changing wheel bearings is no big deal? How big a HF press do you have?
This is a great forum and I'm trying to take in the wealth of information on here from so many great people! Kudo's to all and keep the info coming...I'm only having a hard time getting enough!
#25
01-06-2019, 06:56 AM
Veteran Member
Random ABS warning light illuminations are much more likely due to dirty wheel speed sensors or deteriorating wheel speed sensor wiring harnesses. There are relatively easy fixes for both issues. Search the forum using "wheel speed sensor cleaning" and "wheel speed sensor harness repair" as your search phrases and you will have some very informative reading to do....
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flymyway (01-07-2019)
#26
01-29-2021, 09:29 AM
Junior Member
Your advice was a lifesaver!
Razorboy,
I cannot thank you enough, I had a transmission fault and one mechanic was under the impression I needed a new valve body he said that may be a 50/50 cure if not then I would need to have a rebuilt transmission. I read this post and brought it to a transmission guy and he agreed with you that it was a bad bearing in the right passenger wheel and he replaced the sensor all which was causing weird shifting as well as the ABS and DSC faults and check engine light to be on. If I hadn't read your post I might have went along with the first diagnosis and not been precautious. It's really crazy like you said how this causes all those faults and probably how many ZF transmissions were unnecessarily changed or rebuilt, thank you again!.
I cannot thank you enough, I had a transmission fault and one mechanic was under the impression I needed a new valve body he said that may be a 50/50 cure if not then I would need to have a rebuilt transmission. I read this post and brought it to a transmission guy and he agreed with you that it was a bad bearing in the right passenger wheel and he replaced the sensor all which was causing weird shifting as well as the ABS and DSC faults and check engine light to be on. If I hadn't read your post I might have went along with the first diagnosis and not been precautious. It's really crazy like you said how this causes all those faults and probably how many ZF transmissions were unnecessarily changed or rebuilt, thank you again!.
#27
01-29-2021, 12:32 PM
Veteran Member
One of the real take-aways from this thread is that the rear bearings can be VERY worn and not give much warning. The front bearings will yield the familiar whine, which modulates when steering the car from side to side. The rears however, will degrade tremendously with no audible alert. In my case, the bearings on both sides were so shot that all the components literally fell out of the hub once it was removed. I had to suspect that there was some damage done to the hubs as well, so I went with rebuilt hubs instead of rebuilding my own. They weren’t really that expensive, and along with making the project infinitely less tedious, replacing the hubs as a assembled units was reasonably quick- one afternoon per side. Checking those rear bearings doesn’t take very long, and should be done at least annually.
#28
01-30-2021, 10:05 AM
An add on to the above comment.
The newer scanner software for Jaguar scanners has difficulty with reading ABS / transmission related faults. They either do not read them at all or read them all as Mod fault (safety switch) or transmission failure when the problem may be any number of faults in the ABS system disclosed by the light on and traction failure such as the bearing description above. I have experienced similar problems to those above. Have replaced the transmission and the neutral safety switch. Have not been able to turn off the ABS light. Transmission by local transmission expert, other repairs by local competent general repair.
My local out of dealer Jaguar expert uses a Launch scanner with relatively older software for Jaguar older than 2000. Mine is a 1998 XK8 I have owned for 12 years, it has 97.000 on body 36,000 on engine, I knew the original and subsequent owners personally. Have good records on repair history. ABS fault has been a constant problem for over 18 years. Solutions last a year at most. I have rebuilt the module twice and have a lifetime warranty. Do not believe current problem is the ABS module.
Today my transmission expert use a Launch scanner to pick up Mod fault. While Snapon Triton D-8 at local general repair and Icarsoft i 930 at local non dealer Jaguar repair did not pick up any fault. Still do not know what is causing ABS light and traction failure notice but will begin with bearing failure and work backwards. Have also replaced the four sensors and connectors but believe the sensors, neutral safety switch and transmission I replaced are not the ABS problem.
Will take to expert Jaguar repair shop on Monday.
More as it happens. Thank you for the bearing tip.
Bill
Miami, FL
The newer scanner software for Jaguar scanners has difficulty with reading ABS / transmission related faults. They either do not read them at all or read them all as Mod fault (safety switch) or transmission failure when the problem may be any number of faults in the ABS system disclosed by the light on and traction failure such as the bearing description above. I have experienced similar problems to those above. Have replaced the transmission and the neutral safety switch. Have not been able to turn off the ABS light. Transmission by local transmission expert, other repairs by local competent general repair.
My local out of dealer Jaguar expert uses a Launch scanner with relatively older software for Jaguar older than 2000. Mine is a 1998 XK8 I have owned for 12 years, it has 97.000 on body 36,000 on engine, I knew the original and subsequent owners personally. Have good records on repair history. ABS fault has been a constant problem for over 18 years. Solutions last a year at most. I have rebuilt the module twice and have a lifetime warranty. Do not believe current problem is the ABS module.
Today my transmission expert use a Launch scanner to pick up Mod fault. While Snapon Triton D-8 at local general repair and Icarsoft i 930 at local non dealer Jaguar repair did not pick up any fault. Still do not know what is causing ABS light and traction failure notice but will begin with bearing failure and work backwards. Have also replaced the four sensors and connectors but believe the sensors, neutral safety switch and transmission I replaced are not the ABS problem.
Will take to expert Jaguar repair shop on Monday.
More as it happens. Thank you for the bearing tip.
Bill
Miami, FL
#29
01-30-2021, 11:57 AM
Razorboy,
I cannot thank you enough, I had a transmission fault and one mechanic was under the impression I needed a new valve body he said that may be a 50/50 cure if not then I would need to have a rebuilt transmission. I read this post and brought it to a transmission guy and he agreed with you that it was a bad bearing in the right passenger wheel and he replaced the sensor all which was causing weird shifting as well as the ABS and DSC faults and check engine light to be on. If I hadn't read your post I might have went along with the first diagnosis and not been precautious. It's really crazy like you said how this causes all those faults and probably how many ZF transmissions were unnecessarily changed or rebuilt, thank you again!.
I cannot thank you enough, I had a transmission fault and one mechanic was under the impression I needed a new valve body he said that may be a 50/50 cure if not then I would need to have a rebuilt transmission. I read this post and brought it to a transmission guy and he agreed with you that it was a bad bearing in the right passenger wheel and he replaced the sensor all which was causing weird shifting as well as the ABS and DSC faults and check engine light to be on. If I hadn't read your post I might have went along with the first diagnosis and not been precautious. It's really crazy like you said how this causes all those faults and probably how many ZF transmissions were unnecessarily changed or rebuilt, thank you again!.
One of the things I despise about the internet is the difficulty in finding intel based on search engines. I have devoted countless wasted hours researching topics in a very strategic, search engine manner and it always seems to send me down rabbit holes. That is why I made the subject heading on this post extremely bold. You'll notice I do that with all of my posts since then and this is to "hopefully" make them easier to find when searching.
As you can see from the list of posts past this one, I am no where near finished with the car and its aging issues. Just recently found a bad fuel injector that was prompting a "misfire" set of codes, replaced the fuel pump making a hole in the rear parcel shelf, etc. Since I love the car so much and it is not a car that will rise in value, I have no problem painting outside the lines when it comes to servicing it. I made my own cold air intake setup for a fraction of what it costs to buy one off the shelf and my next major DIY job on the car is rebuilding the entire exhaust system myself and my trusty MIG welder. Outside of that task, I have some simple maintenance items to handle and then, if the car lasts that long, I will be sending it in for a full respray. Stay tuned for that
Congrats to anyone that has been able to use my post to save money and keep these cars on the road. I can only imagine how many of these beautiful machines were scrapped because of a simple issue like this and receiving bad or false information from mechanics who we feel we should be able to trust. Don't get me wrong, there are many amazing shops out there but some of them simply do not know of particular issues like this and so take traditional routes like swapping the transmission out.
I admit it has been warming to see people finding out that they were suffering from the same issue.
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michaelh (01-31-2021)
#30
01-31-2021, 02:37 AM
Junior Member
#31
01-31-2021, 03:22 AM
#32
01-31-2021, 03:46 AM
Senior Member
Tony, The bearing sets are relatively inexpensive; labor is the bigger cost. Plan on replacing both the inner and outer bearings at the same time while you've got everything apart, then you won't have to worry about either of them for another 100,000 miles (more or less; your mileage may vary). You can purchase kits complete with bearings, seals, and a new spindle nut (absolutely necessary) from our forum vendors or other sources. You might also be ready for new parking/emergency brake pads and this would be an ideal time to replace them, too.
#34
02-13-2021, 09:01 AM
Follow-up to Neutral Safety Switch
When I replaced the transmission, the ABS light came on. The scanner at my local repair shop said it was the mod switch. I took it back to the transmission shop. I bought the switch that fits on the transmission for $495 on eBay and the shop installed for two hours labor. ABS light went off for a day then came back on. Code 1155, front left wheel sensor. Bought that with connector for $78 and local repair shop installed for 3/4 hour labor. ABS light stayed on. No reading on scanner at local repair shop. Took back to transmission shop. Scanner said mod switch. Must be careful on mod switch readings, same reading for switch on transmission and switch on gear shift leaver. Replaced connector to gear shift leaver and ABS light has gone off. Moral to story. ABS light is a difficult problem to solve. I had the module rebuilt twice before the real problems surfaced, transmission failure main issue, sensors secondary issues. Difficult because Blue Book on a 1998 with a new transmission is $9,000 approx with tranny and ABS related repairs $4,000. That is why so many of these cars are leaving the road. Believe those of us who hang with it will see value go up soon.
#35
02-13-2021, 04:36 PM
Razorboy, You Sir are truly sharp, LOL (pun intended) That was a boatload of info I will make use of. I have no issues with my '03 base Conv. at the moment but I will check the wheel bearings just the same as an once of prevention. I have done the filter and fluid change on mine and it is butter smooth.
I came across this thread since it went to the top of the new stuff when someone else replied and I'm glad it did. I agree whole broken heartedly at the thought of another car being given up on and junked at the cost of repair on a miss diagnosis, what a shame. Enjoy and keep it coming. Thanks.
Hi, my name is Tom (hi tom) and I'm a Jagoholic.
I came across this thread since it went to the top of the new stuff when someone else replied and I'm glad it did. I agree whole broken heartedly at the thought of another car being given up on and junked at the cost of repair on a miss diagnosis, what a shame. Enjoy and keep it coming. Thanks.
Hi, my name is Tom (hi tom) and I'm a Jagoholic.
#36
02-16-2021, 01:39 PM
Senior Member
Adding my thanks and kudos to Razorboy; my barn-find 05' started intermittent "Check Rear Lights" and "Cruise Not Available" warnings on a 600 mile trip, just one year after replacing the brake switch with a rebuilt one. No limp mode and no transmission error codes, but lots of pucker factor out in the Mojave Desert between Las Vegas and Palm Springs, CA. The warnings eventually cleared themselves after about 100 miles, but reappeared on more occasions. From prior experience I knew I could get the car home ok, but researching posts to cover all the bases, I read through this thread. It prompted me to jack up and check the rear wheels, only to find substantial play in the driver's (left) side bearings, and minimal-but-noticeable play on the passenger side (car has 106,000 miles on it). Being that there was no grinding or squealing in the bearings at slow speeds, I managed to get it home to Las Vegas via back roads without burning anything up. I don't own a press so I took the car to Top Car Service on N Nellis in Las Vegas, (great no-frills service, very honest, very fair), and had Roje replace the wheel bearings for me, as well as the parking brake pads, (good time to get them done...). Now, no more warnings and I'm preparing for a 4,000 mile Great Northwest Tour this summer. I'm glad that I didn't have to go through the nuisance of replacing the brake switch again (though I'll carry a spare in the wheel well going forward), and glad that the rear bearings are good for another 100,000 miles. I would advocate that checking (and replacing) the rear wheel bearings in any X100 that has 90,000 miles or more on it will help avoid a myriad of potentially expensive false errors. Thanks, Bernie!
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razorboy (02-17-2021)
#37
02-16-2021, 01:55 PM
Veteran Member
#38
09-11-2021, 12:05 AM
Really need your help.
Hi Lads,
If you do a search on Razorboy threads, you will see plenty on my transmission issues.
I am being dramatic on the title to make certain that anyone who is encountering issues such as I have - at least takes a look at this and maybe save many thousands of dollars.
Going to bullet a lot of this to speed up the read for you too: ......
If you do a search on Razorboy threads, you will see plenty on my transmission issues.
I am being dramatic on the title to make certain that anyone who is encountering issues such as I have - at least takes a look at this and maybe save many thousands of dollars.
Going to bullet a lot of this to speed up the read for you too: ......
Hi! Reading your brief story for a moment i think that it is about me.
I have the same story like your with few differences. Try to be short.
I bought xk8 2005 with 150k miles on it.
From the beginning it had knocking sound from rear driver side, making me crazy while driving until now. Transmission has 3-4 gear ratio fault. Triggering on the road 4-5-6 at lower speed. Knock from 2-1 when stop.
Took the car to mechanic, advise was full rebuilt of transmission.
Having rear knocking sound at the same time, took car on the jack.
1. Changed transmission all solenoids with new, new oil pan, socket and fluid
2. Disconnected rear shock lower bushing on the jack to see if the sound is comes from upper or lower bushing, or shock by itself.
all the mentioned looked good for first time.
Then replaced rear stabilizer bushings, thinking that possible sound can be stabilizer.
At the end of fix, figured out that rear wheels have noise when pulling up and down keeping hand from upper and lower parts of wheel.
i was surprised that found the problem.
After transmission fix drive about 500 miles, completely different transmission, like new.
Ordered rear bearings, took to mechanic to replace them, (with hope that i found the problem and will finish this all story, and really tired to fo any work on the car), after complete replacement the knocking sound was the same, even more, which make me upset.Mechanic recomend me to change one shock with new one, to see the difference, motivated that sound more likly is shock or rear axle.same time changed 4 tires With new with correct size, as previous was wrong and same big size( think myself that it can have influence on ABS sensors, giving wrong information, having trans issues).
driving home started to thing, maybe he did something wrong with bearings, as the sound is more now, maybe damaged abs sensors while replacing bearings.
by the way home transmission started triggering, came home check the code was p0706, checking ABS everything fine, trying to check while driving, all 4 sensors showing same speed.
Before reading your post i was thinking to change new transmission and ordered new shock for back, will try to change next week.
but now i am starting to think more that all this story is comming from rear bearings and ABS sensor, ( as i don’t have any fault codes) any way i think that the sound from bearings and transmission fault is coming from sensors.
What is your opinion in this situation, what to do next, try to change bearings again ti be sure that sound went off??????, and there will not be possible vibration for sensors?
your experience and advice will be much appreciated
Last edited by GGG; 09-11-2021 at 12:21 PM. Reason: Shorten the QUOTE
#39
09-11-2021, 01:43 PM
Junior Member
Shifting issue
Hi Lads,
If you do a search on Razorboy threads, you will see plenty on my transmission issues.
I am being dramatic on the title to make certain that anyone who is encountering issues such as I have - at least takes a look at this and maybe save many thousands of dollars.
Going to bullet a lot of this to speed up the read for you too:
1) Bought 2003 Jag XK8 couple of years ago with 120k on the clock. Needed work but seemed to drive decent from SoCal to Las Vegas
2) With 120k on the clock, I decided to do the transmission service and I had a little bump going from 2nd to 1st like pulling up to Stop signs.
3) Shortly after transmission service using Mercon SP and new filter, I went on the hwy and in a kickdown from 6th to 5th saw my first transmission fault indicator.
4) Emptied and refilled transmission again thinking I needed more old fluid out. The stuff that came out originally was pretty dark
5) 2nd to 1st bump got better but it was obvious something wasn't right. Continued to throw transmission faults that would reset after the car sat for a few minutes
6) Purchased JLR software from Britain after research and used it to clear the adaptive memory and start over. Also got the codes with the primary ones being gear ratio faults and output speed sensor faults
7) Had basically convinced myself that the issue was either the valve body or the guts of the transmission itself but I saw no particles to speak of in the transmission fluid or on the magnets in the filter.
8) Continued to struggle with the transmission but seemed to get away with using the J-Gate to shift for a while. Finally just parked the car in preparation for what to do next
9) Used the car here and there for limited runs until the day came where everything went ape-****. Transmission fault, DSC and ABS fault, limp home mode deluxe
10) Discovered intel on the seals between the valve body and the transmission as a possible problem so I ordered them in and cracked the pan off again
11) Pulled the valve body and decided to take it local and have it tested by a ZF certified valve body specialist. He called and said that the E-clutch circuit should be providing about 200psi of pressure - it was producing nothing - I jumped for joy.
12) Coughed up 1000 dollars to have the valve body completely rebuilt with all original ZF parts. Figured I couldn't go wrong and if I needed to replace the transmission, I would have a fresh valve body to go with it.
13) During all of this time, I had a rattle in the drivers rear corner. I thought it was a loose shield or maybe a suspension bushing but ignored it as I had bigger fish to fry with the transmission
14) After getting the fresh valve body back in, I took the car for a test drive. It was different a bit but it didn't take long before the faults happened again and I now had a wheel speed sensor fault on the drivers rear?
15) Decided the easiest thing to do was to swap the rear sensors around which I did and got another fault. Same wheel so I knew it wasn't the sensor and the JLR live data confirmed that all sensors were generating like signal
16) Don't really know what triggered it but I had an epiphany and jack the rear of the car up and moved the rear wheel. I had a LOT of play in the rear wheel bearing on the driver side and a healthy amount of play on the passenger side rear as well. Fronts were solid.
17) I started pondering about this and the transmission faults but especially the DSC and ABS faults as the wheel bearing issue would most certainly put the phonic wheels out of alignment with the sensors. Ordered new wheel bearing kits for both sides
18) Did the passenger side first which was pretty straightforward but the driver side was in rough shape. I had to use a 3 lb sledge and a drift to knock the hubs out of the very damaged inner bearing and the outer bearing wasn't much healthier. Got it all back together and dropped the car to the deck for the first run.
I went out on the test drive with absolutely no expectations other than maybe this was what was making the rattling noise in the rear and I was right. The rattle had completely disappeared BUT so had all of the transmission issues!! I had considered that this might be a very slight possibility not knowing exactly the logic behind the sensors, ECU and TCM.
Now hindsight is 20/20 but I scoured the internet for months and asked hundreds of questions even on this site and from gurus and not one person brought up the possibility that the issue could have been wheel bearings but yet that's exactly what has caused all of my issues with the transmission for so long. I have gone on three 30 mile + runs and have not witnessed a single shift issue, no faults and even the 2nd to 1st bump is non-existent. The transmission feels as though it is all brand new again and believe me when I say that this is not a statement of a mild improvement, this is absolutely cured of its issues. I have put nearly 100 miles on the car since yesterday and have witnessed zero issues and before the problems would have started before I got to the end of my street.
So here is my breakdown of the problem and the cure that I discovered:
All four wheel speed sensors feed data back to the computers for various reasons. What the direct correlation is between them and the TCM is not exactly clear but obviously there is a relationship
I assume that there is enough backup / averaging in the computers to compensate for a single bad wheel speed sensor but what about two of them? Meaning both rears not sending consistent signals? The computer sees the sensors working because they were but the sensors are obviously out of physical alignment to the phonic wheels and because there is play in the bearings, the wheel jumping up and down while driving may be presenting some very messed up data that the computers cannot resolve which causes errors which leads to assumptions by the computer about what is wrong. It also means the inaccurate data screws with the TCM and because of that causes inadvertent shift activity leading to other codes and ultimately transmission faults. In hindsight, the DSC and ABS faults were clear indicators that a wheel bearing or sensor issue was in play but how much that mattered to the TCM was unclear to me until now. Turns out it is VERY important
Now I sit and wonder a few things:
1) Is this a forever fix? I haven't really put my boot into it yet but simply drove normally all the way up to 80mph on the freeway without a glitch. Before as I said I couldn't get to the end of my street without some weird buck or shift. I will hold out final judgement for a few days as the transmission may have suffered internal damage because of this issue but again I say that this fix is not subtle - its an astonishing change
2) I wonder how many ZF transmissions have been swapped out over the years because of a misdiagnosis on this issue. I was days away from buying a rebuilt transmission and getting into a lot of labor to swap it out.
Guys, look for my threads and see how long I dealt with this and how much effort I put into finding the REAL fix.
I simply advise anyone throwing faults on their transmission to do this before you try anything else. Just jack up each corner of the car and placing your hand on the top and bottom of the tire, rock the wheel in and out. You should only feel a very slight amount of play in the wheel bearing. If there is any more that half a millimeter lets say, you should start by having the offending wheel bearings replace. Do not and I repeat do not run to the nearest dealership for a new transmission until you completely, 100% certain that all wheel bearings and all wheel speed sensors are in perfect health.
For me this journey has ended:
Gear Ratio Faults - gone
Transmission output speed sensor faults - gone
Wheel speed sensor faults - gone
Weird shifts and bucking sometimes between gears - gone
2nd to 1st gear bump - gone
RPM flaring between 3-4-5 shifts - gone
DSC and ABS warnings - gone
thousands of dollars for a transmission - still in my pocket
Car now hauls ***
I hope someone out there gets the most out of this thread. Although its too late to help me, I hope it saves someones *** one day so it was worth writing every single word.
Possibly my biggest forum contribution ever!
If you do a search on Razorboy threads, you will see plenty on my transmission issues.
I am being dramatic on the title to make certain that anyone who is encountering issues such as I have - at least takes a look at this and maybe save many thousands of dollars.
Going to bullet a lot of this to speed up the read for you too:
1) Bought 2003 Jag XK8 couple of years ago with 120k on the clock. Needed work but seemed to drive decent from SoCal to Las Vegas
2) With 120k on the clock, I decided to do the transmission service and I had a little bump going from 2nd to 1st like pulling up to Stop signs.
3) Shortly after transmission service using Mercon SP and new filter, I went on the hwy and in a kickdown from 6th to 5th saw my first transmission fault indicator.
4) Emptied and refilled transmission again thinking I needed more old fluid out. The stuff that came out originally was pretty dark
5) 2nd to 1st bump got better but it was obvious something wasn't right. Continued to throw transmission faults that would reset after the car sat for a few minutes
6) Purchased JLR software from Britain after research and used it to clear the adaptive memory and start over. Also got the codes with the primary ones being gear ratio faults and output speed sensor faults
7) Had basically convinced myself that the issue was either the valve body or the guts of the transmission itself but I saw no particles to speak of in the transmission fluid or on the magnets in the filter.
8) Continued to struggle with the transmission but seemed to get away with using the J-Gate to shift for a while. Finally just parked the car in preparation for what to do next
9) Used the car here and there for limited runs until the day came where everything went ape-****. Transmission fault, DSC and ABS fault, limp home mode deluxe
10) Discovered intel on the seals between the valve body and the transmission as a possible problem so I ordered them in and cracked the pan off again
11) Pulled the valve body and decided to take it local and have it tested by a ZF certified valve body specialist. He called and said that the E-clutch circuit should be providing about 200psi of pressure - it was producing nothing - I jumped for joy.
12) Coughed up 1000 dollars to have the valve body completely rebuilt with all original ZF parts. Figured I couldn't go wrong and if I needed to replace the transmission, I would have a fresh valve body to go with it.
13) During all of this time, I had a rattle in the drivers rear corner. I thought it was a loose shield or maybe a suspension bushing but ignored it as I had bigger fish to fry with the transmission
14) After getting the fresh valve body back in, I took the car for a test drive. It was different a bit but it didn't take long before the faults happened again and I now had a wheel speed sensor fault on the drivers rear?
15) Decided the easiest thing to do was to swap the rear sensors around which I did and got another fault. Same wheel so I knew it wasn't the sensor and the JLR live data confirmed that all sensors were generating like signal
16) Don't really know what triggered it but I had an epiphany and jack the rear of the car up and moved the rear wheel. I had a LOT of play in the rear wheel bearing on the driver side and a healthy amount of play on the passenger side rear as well. Fronts were solid.
17) I started pondering about this and the transmission faults but especially the DSC and ABS faults as the wheel bearing issue would most certainly put the phonic wheels out of alignment with the sensors. Ordered new wheel bearing kits for both sides
18) Did the passenger side first which was pretty straightforward but the driver side was in rough shape. I had to use a 3 lb sledge and a drift to knock the hubs out of the very damaged inner bearing and the outer bearing wasn't much healthier. Got it all back together and dropped the car to the deck for the first run.
I went out on the test drive with absolutely no expectations other than maybe this was what was making the rattling noise in the rear and I was right. The rattle had completely disappeared BUT so had all of the transmission issues!! I had considered that this might be a very slight possibility not knowing exactly the logic behind the sensors, ECU and TCM.
Now hindsight is 20/20 but I scoured the internet for months and asked hundreds of questions even on this site and from gurus and not one person brought up the possibility that the issue could have been wheel bearings but yet that's exactly what has caused all of my issues with the transmission for so long. I have gone on three 30 mile + runs and have not witnessed a single shift issue, no faults and even the 2nd to 1st bump is non-existent. The transmission feels as though it is all brand new again and believe me when I say that this is not a statement of a mild improvement, this is absolutely cured of its issues. I have put nearly 100 miles on the car since yesterday and have witnessed zero issues and before the problems would have started before I got to the end of my street.
So here is my breakdown of the problem and the cure that I discovered:
All four wheel speed sensors feed data back to the computers for various reasons. What the direct correlation is between them and the TCM is not exactly clear but obviously there is a relationship
I assume that there is enough backup / averaging in the computers to compensate for a single bad wheel speed sensor but what about two of them? Meaning both rears not sending consistent signals? The computer sees the sensors working because they were but the sensors are obviously out of physical alignment to the phonic wheels and because there is play in the bearings, the wheel jumping up and down while driving may be presenting some very messed up data that the computers cannot resolve which causes errors which leads to assumptions by the computer about what is wrong. It also means the inaccurate data screws with the TCM and because of that causes inadvertent shift activity leading to other codes and ultimately transmission faults. In hindsight, the DSC and ABS faults were clear indicators that a wheel bearing or sensor issue was in play but how much that mattered to the TCM was unclear to me until now. Turns out it is VERY important
Now I sit and wonder a few things:
1) Is this a forever fix? I haven't really put my boot into it yet but simply drove normally all the way up to 80mph on the freeway without a glitch. Before as I said I couldn't get to the end of my street without some weird buck or shift. I will hold out final judgement for a few days as the transmission may have suffered internal damage because of this issue but again I say that this fix is not subtle - its an astonishing change
2) I wonder how many ZF transmissions have been swapped out over the years because of a misdiagnosis on this issue. I was days away from buying a rebuilt transmission and getting into a lot of labor to swap it out.
Guys, look for my threads and see how long I dealt with this and how much effort I put into finding the REAL fix.
I simply advise anyone throwing faults on their transmission to do this before you try anything else. Just jack up each corner of the car and placing your hand on the top and bottom of the tire, rock the wheel in and out. You should only feel a very slight amount of play in the wheel bearing. If there is any more that half a millimeter lets say, you should start by having the offending wheel bearings replace. Do not and I repeat do not run to the nearest dealership for a new transmission until you completely, 100% certain that all wheel bearings and all wheel speed sensors are in perfect health.
For me this journey has ended:
Gear Ratio Faults - gone
Transmission output speed sensor faults - gone
Wheel speed sensor faults - gone
Weird shifts and bucking sometimes between gears - gone
2nd to 1st gear bump - gone
RPM flaring between 3-4-5 shifts - gone
DSC and ABS warnings - gone
thousands of dollars for a transmission - still in my pocket
Car now hauls ***
I hope someone out there gets the most out of this thread. Although its too late to help me, I hope it saves someones *** one day so it was worth writing every single word.
Possibly my biggest forum contribution ever!
Your description here describes my issue exactly! I will replace the bearings and update later! THanks Thanks Thanks!
#40
09-11-2021, 06:59 PM
Veteran Member
Ditto to all. The first indication of my problems was a Tranny fault and limp home mode. It said something about 4th gear. The solution was a rebuilt driver side rear bearing hub. The second indication was a loud rasping coming from the passenger side some years later. That bearing was going as well and causing the new (thicker) disc to rub against the Brembo caliper. Rebuilt that hub and all problems gone. Those fixes and two or three mercon sp flushes and the car couldn’t have been any sweeter. Definitely check your rear bearings first whenever you have a Tranny fault!!!!