Tranny Trouble
 

I put the scanner on and read 0776, 0776 pending, 1000, 1775. It is a 1996 XJ12, a long body. Cleared the codes and started the car. It immediately came back with 1000 and 1775. I live in central Oregon so Jag mechanics are really hard to come by. The scanner says the 0776 is something about a B valve. Hmm, probably time to sell :icon_confused:. Want to buy? Make an offer!

Thanks for reading my post. Any help would be greatly appreciated.

Dennis M.

Perhaps "B Solenoid"?

The "A and B Shift solenoids" often give trouble, as to the front and rear speed sensors. For about $120 or so you can buy all four parts. A bit of a messy chore as the pan has to be dropped...but perfectly DIY-able. As guesswork repairs go it isn't hateful, at least in terms of parts expense.

A better first step would be to carefully examine the wiring and connector at the transmission. A weak trans mount can allow the transmission to move up-down too much, over-stretching the wiring, causing damage. Fairly common problem.

Cheers
DD

I meant to add that if you don't want to DIY the type of work I just mentioned is routine for anyone familiar with GM transmissions. A Jag specialist is not needed.

Cheers
DD

Don't worry about P1000. That only means the drive cycle is not completed. When it is, P1111 will display. Then it will be ready for emissions testing (as long as Check Engine light is still off).

I concur, tranny sensors and solenoids go foul. I plan on doing my own, although for now I don't have a problem other than a delay when engaging drive.

You can use the Private 'for sale' section on the forums here, if you really want to sell. Keep in mind that wherever you advertise, you will face a much harder sale if there is a driveability problem. Truth is, these cars are not easy to sell even when they run great. There is simply not a lot of demand for them. Most shy away due to the urban legends of the Jaguar V12. I suppose some of those legends are true, although NOT for the last generation XJ12!

I appreciate the help. It doesn't sound that bad. I am going after the wiring first. The transmission was replaced about 40K miles ago and it occasionally has done some odd things associated with the electronics. The car runs great though and I really want to keep it.

Thanks again.

Ok! There are so few of these cars on the road, and they all need someone to care about them and keep them on the road. Looks like that's you and me! This last gen XJ12 is somewhat of a novelty, but certainly a terrific way to travel.

X305 Transmission Pan Removal
 

I found that in order to access the external speed sensors, the harness connector, or to drop the transmission pan, the exhaust needs to come down. Oh, dread!!
I decided to cut the pipes at four locations using a sawzall- just aft of the front downpipes and at the rear about 3" ahead of the rear center hanger. I bought four 3 bolt flange kits (Google Patriot H7258) and welded those. I tacked them securely with the exhaust held in position, then removed it all to finish half of the welding on the floor. If you are using MIG, be sure to attach the ground clamp to each of the four flanges on the car so you don't send voltage surges through the chassis and electronics!
The rear O2 sensors must be unplugged prior to the drop, but are easy to unplug by dislodging the rubber grommets and pulling the two harnesses out of the floor until the connector can be undone.
Once this mod is complete, dropping the whole center of the system is a 15 minute job, but a helper is useful.
Once this assembly is out of the way, access is significantly improved. To access the rear harness connector you still have to support the rear of the trans and remove the rear mount.
Almost nothing on this car is easy to access.

X305 Transmission Pan Removal-Addendum
 

I cut the front pipes just aft of the front cats. Try to cut 90 degrees to the pipe, and pick a spot that leaves room for the flanges and to weld them in.
A rather tedious process but sure worked well for me.

So while backing my car out of the shop the other day I got a few 17XX P codes. So right back in she went. Replacing the solenoids was real straight forward and only cost 95 for everything including speed sensors. Mine had a nice reusable gasket for the pan. You will lose about 4 quarts of fluid. I like to use a Lowe’s hardware paint bucket to measure the amount that comes out so I know just how much to put back in.
https://www.ebay.com/itm/322922640023

It is also possible to do this without removing the exhaust. Though the speed sensors will be really difficult to replace but it is possible with the right combination of extensions and elbows and curse words. See photo below.

The clips on the wiring harness where they connected to the solenoids were all brittle and broke when removed no matter how careful I was. So using needle nose pliers, I made sure the metal connectors slid on real tight by bending the tabs down on the wires so there was little clearance to slide them on. Also followed up with zip ties. I just didn’t want to spend 250 on the jag specific internal wiring harness.

About a 4 hour job with the majority of the time spent on the speed sensors. Make sure you have a good torque wrench that goes down to inch lbs for the manifold pressure switch bolts. It’s real important this is right.
https://cimg7.ibsrv.net/gimg/www.jag...66bbf0b58.jpeg
The combination I had to use to get the speed sensors out.
https://cimg1.ibsrv.net/gimg/www.jag...1ebe79dd8.jpeg
Old solenoids and manifold pressure switch which should always be replaced.
https://cimg5.ibsrv.net/gimg/www.jag...5c9851d96.jpeg
With everything removed. Some great videos on YouTube that show how each solenoid comes out.
https://cimg6.ibsrv.net/gimg/www.jag...2cf71dbe6.jpeg
Speed sensor removed hole that isn’t fun or easy to access
https://cimg2.ibsrv.net/gimg/www.jag...b3b9ea7fe.jpeg
This connector needs to be ground flat on one side to fit on the new solenoid.

G'day Gents,

I've recently had the 4L80E autobox in my X305 rebuilt after years of problematic operation which slowly got worse and eventuated in the rebuild.

As soon as I described the symptoms to the technician he said it's probably your AFL valve. WTF is that I asked?

This following article explains it all better than I could, the AFL valve apparently is a horizontal steel shuttle valve which runs in the light alloy valve body and eventually wears the operating cylinder out of round and then problems start to appear. Anyhow here is the article.

AFL Valve.

1993 to 2018 General Motors vehicles equipped with 4L60E, 4L65E, 4L70E, 4L75E and 4L80E automatic transmissions often wear out the actuator feed limit (AFL) valve bore. As a result, inadequate pressure rise and shift solenoid feed oil loss can occur. This can cause trouble codes, wrong gear starts, falls out of gear and clutch plate burn-up.

The purpose of the actuator feed limit valve is to limit the pressure going to the actuators (aka shift solenoids). The AFL valve spring is calibrated to prevent the pressure from ever exceeding a predetermined pressure, no matter what the main line pressure is. This is necessary to prevent more fluid from being fed to the solenoids than they can physically exhaust and to limit the maximum line pressure output.

On one hand, if the pressure feed to the ON/OFF shift solenoids is higher or lower than intended, the shift valves controlled by those solenoids may not do what they should. For example, too much pressure could flood the shift solenoids, making them act as mechanically stuck closed solenoids. Alternatively, not enough pressure could make them act as mechanically stuck open solenoids. As a result, the transmission can have wrong gear starts, or fall out of gear.

On the other hand, for pulse width modulated (PWM) solenoids like the line pressure control solenoid (PCS), if the feed pressure is too high or too low, the consequences can be detrimental. The PCS output controls the line pressure based on the calculated load from the computer. Consequently, if the AFL pressure feeding the PCS solenoid is too high or too low, the line pressure output will also be too high or too low. As a result, the transmission will either slip and burn frictions, or have hash shifts.


PWM/TCCValve

1991 to 2013 newer General Motors vehicles equipped with 4L80E and 4L85E automatic transmissions often wear out the torque converter clutch (TCC) regulator valve bore in the valve body.

The TCC regulator valve function is to regulate the torque converter clutch apply pressure. The computer varies the pulse width modulation of the TCC PWM solenoid, which regulates the apply pressure of the lock-up clutch. Because of the constant PWM solenoid induced oscillation, over time, excessive wear of the bore occurs. As a result, the computer loses the ability to control the lock-up clutch apply rate and slip rate properly due to the loss of TCC apply pressure.

I hope this info is helpful, cheers,
Jeff.

P.S. If I'd had the AFL valve fixed years ago I probably wouldn't have needed the rebuild. BTW the car has over 220,000 miles on it and now going better than ever.

P.P.S. Fault codes indicating dodgy shift solenoids will be displayed but changing them, which I had also tried, will make no difference because the dodgy AFL valve is the culprit.

P.P.P.S. I had replaced the internal harness years ago and that made no difference and while at it I removed the external harness and tested it for continuity from the tranny plug to the other inner plugs and couldn't fault it even when wiggling the harness to try and reveal any broken wiring. Interestingly when the autobox repairer re-installed my tranny there was suspect connection between the tranny and the ECU. After considerable investigation it turned out to be a slight mismatch between the pins at the internal/external harness connector. Re-pinning the external plug sorted that problem out.

So I think I might have had this AFL valve issue. My shifts from 2-3 were getting more and more "pronounced" when the engine was warm. Also had a few times when cold it didn't shift at all and threw a fault that cleared after shutting down and restarting. I decided a valve body swap was the best option since I wanted to do the work myself didn't trust myself to do the full rebuild. I found one for 250 bucks from what seemed like a reputable seller(world wide specialty parts). Gotta love having a GM tranny. It has new solenoids and all the upgrades. I wish I had just done this and swapped the speed sensors the first go around with this transmission.

Wasn't too bad swapping it out. Cleaning off the old gaskets with a straight razor that were sandwiched between the valve body plate was probably the most tedious task. That and getting it back on while holding down a large spring loaded valve was tricky. Make sure you don't lose the 9 check valve balls that sit on top of the valve body. I'll post some photos below that show the correct placement of these balls. Also make sure you take plenty of pictures before removal of where all the bolts and attachments correctly go.

Reset the TCM and now it seems to be shifting a whole lot smoother. Takes about 4.5 quarts of Dextron III after the swap. Will update if any issues pop up.

***Update my reverse doesn't work now!!*** It appears they forgot to install a necessary check sleeve and ball inside the valve body.




https://cimg7.ibsrv.net/gimg/www.jag...c8f6408122.jpg
https://cimg8.ibsrv.net/gimg/www.jag...c064a92920.jpg

Hows the transmission doing now @John Baker? Did you get the valve body corrected and activate reverse gear?

Thanks for the heads up on that. Website is current, they are on eBay too. Looks like a great deal so I'm considering "trying" it.

My question is, could the above discussed AFL valve and/or other valve body parts cause a sudden total loss of forward (Drive) gear engagement? Despite Reverse gear working properly? Probably hard to know for sure. ASKING FOR A FRIEND. :icon_eek:

Mild Thread Revival Here:

@John Baker For the valve body you purchased, was it just the standard 1993-1996 4L80E valve body or did it fall into a different year range?

I'm about to purchase one to see if it will smooth out my slightly abrupt 2-3 WOT change.

There was a change during X305 production with the orange dot addressing shifting

It may have involved the valve body

08-2-03 (jagrepair.com) :icon_dance-disco:

Hmmm. Well, my trans dosen't have the orange dot and considering that my trans number is 95ZJP4165 and my car has an Aug 1994 production date, I suspect that it's still original. That being said, I'm sure it's fine, I just wanted to see if a valve body would potentially smooth out my 2-3 WOT shit and some harsh reverse engagement (no delay).

I think it would be a good idea for everyone to replace their valve body now. At this age many trouble spots can develop and will continue to get worse. It is the heart of the transmission, so to speak. World Wide's listing is specially for Jaguar, if you didn't see it yet:

World Wide Specialty Parts GM/Jaguar Valve Body

Seems a little more promising than buying a "generic" rebuilt unit. $250 well spent on a "heart transplant" could possibly avoid a total transmission rebuild. It shouldn't cost much for a shop to do it either. It was too late for me but I did get a rebuilt valve body as part of my $3000 total rebuild!

I saw their eBay listing which appeared to be quite a bit more expensive for the Jaguar-specific one! I went ahead and ordered one directly through their site yesterday and paid an extra 100 dollars for the lifetime warranty. Probably not neccessary, but the peace of mind in case something goes haywire further down the road is pretty worth it to me.

Since I'll be dropping both the front and rear subframes this summer for the full mechanical refresh, doing the valve body "while I'm in there" seems like a prudent idea lol.

Update on my new valve body:

For the most part, the car shifts significantly better than before, even though it was not that bad to begin with. Engaging Reverse and Drive are as instant as before but far smoother and upon initial driving, the shifts are so smooth, they're practically undetectable!

However (and there always seems to be), it dosent stay smooth. If you drive the car normally/gently, it will shift perfectly normal. But if you expose it to a long grade (the only way in and out of my parents town) or give it a little bit of spirited driving on back roads (but far from giving it the full Stirling Moss) it starts to act weird. Shifts become harder, theres an occasional/unpredictable slip from 2-3, harsh reverse/drive engagement, and it starts off in 1st despite being in Normal mode. If I drive it extremely gently for a bit, it will then start to act normally again. I thought this might be due to the transmission fluid level, but after readjusting it about 6-7 times, I still can't seem to get a consistent reading (will either be way to high or way too low. No in between or even close to the hot marks) and the symptoms still re-appear at consistent points in my test drive loop. Additionally, its not throwing any codes. Just P1000.

I put about 175 miles on it with various attempts to re-level the fluid (following the instructions in the VSM to the letter) to no avail. Any thoughts?

Strange about the changing fluid level. It should be made correct before any troubleshooting can take place, but if you can't get it correct??

The ECUs have adaptability and learn to accommodate your driving style. That might be a source of the "different" feel to the shifts as you change up your style.

Any fault codes or limp home incidents? The Transmission ECU had a EPROM update via TSB to the BSKK version, do you have it? That was mainly due to some phantom codes coming up, as far as I know.

Ask Worldwide for advice. Maybe you have to drain, measure and refill the transmission oil again to get the correct amount and just ignore the dipstick reading. I know, easier said than done.

In terms of the fluid level, I'm at my wits end with it. A neighbor of mine runs a highly respected transmission shop so it will be going to his place once he has availability to check/possibly change the fluid so I have an accurate benchmark for us to move forward diagnosing it. Its super frustrating since...its just a fluid level. This should be the simplest part of the job, yet somehow I still can't seem to ever come close to getting it right!!!

The TCM learning sounds very much like whats going on here. But the shifts are beyond "different" and just downright don't feel right. Considering it will start starting off in 1st despite being in normal mode I think indicates something beyond adaptation. I did find a document on JagRepair.com from 1996 that states the that TCM will go into a "Default mode" (different from Limp home mode) that will substitute default values when the TCM registers a non-serious fault. Apparently this clears after a key cycle and no codes or lights are illuminated. It does mention that shift quality will deteriorate in this mode, but makes no mention of Default mode implementing a 1st gear start program.

I don't think my car has had the EPROM update. I didn't notice a sticker for it on the TCM or any documentation. It also dosent look like the parts are available to do that anymore...cool.

No lights, no transmission related codes, no instances of Limp home mode. Just this occasional onset of it being upset.