When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Only thing I'm unsure about is 'Reduce the Throttle Angle until the torque converter locks' and hold it for one minute. Is that when the box is in 6th? I understand the principle of the lock up but never done it before and don't know what to expect/look for?
Hi Paul,
That is a description of the conditions that will trigger the P0783 code so a technician can duplicate the fault, but you don't have to worry about that.
Let us know what you find when you detach the electrical connector. Also, have you checked the ECM connector for water ingress?
I could not find any pinpoint tests for P0783 in the Workshop Manual, but I did find this explanation in the Transmission DTC Summaries manual (attached):
Based on the above, mhamilton's suspicion of low fluid could be a good call, since that will cause slippage.
Hi Don. Yes, I think mhamilton's call was a good shout too as I have a theory that the fluid is leaking from the connector (especially going up that steep hill), and running onto the exhaust, hence all the smoke and smell of the burning oil. If it's been leaking a lot, then the fluid is likely low, and/or your comments that the connector pins could be soaked in fluid. I guess one of these conditions could cause the problem let alone both. Just to clarify, when my scanner found the fault it said "P0783 Gear Load 3-4".and 3rd to 4th is where I appear to be having the problem changing. If the fault appears the gearbox will not shift to 4th.
I think the best way forward at the moment is to replace the connector sleeve and service parts you have mentioned, put the new pan/filter on and hopefully the ATF should be sealed in... then go from there? Changing the parts mentioned can only be good practice anyway, and illiminates them being the cause?
I have access to the lift this coming week, it makes it a much easier job than jacking the car up on stands. I will let you all know what I find but judging by the amount of smoke I do expect that connector to be leaking badly to be honest! I also know after checking it's not the pan/filter that's leaking.
Paul
Have you studied the procedure for setting the fluid level?
The first thing to be prepared for is how to open the fill plug on the right side of the transmission. I ground the short leg of an 8 mm Allen wrench to about 13 mm - 1/2 inch long so it would fit between the transmission and exhaust pipe:
Be sure you can loosen the fill plug before you remove the drain plug. Finding out after you've drained the fluid that you can't remove the fill plug will ruin your day.
ZF states that the fluid level is set with the fluid temperature between 30°C and 50°C. Run the engine and monitor the transmission fluid temperature. When the fluid reaches 30°C, remove the fill plug and confirm that fluid spills out. If no fluid emerges, add more fluid (with the engine still running or you'll lose too much fluid). When the temperature reaches 40°C and fluid is just trickling out, replace the fill plug. If the fluid temperature exceeds 50°C, you have to reinstall the fill plug, shut off the engine and allow the transmission to cool, then start over. Personally, I try to set the fluid level at closer to 30°C, since this results in the highest "correct" fluid level.
If you use an infrared thermometer to measure fluid temperature, aim the thermometer at the fluid dripping from the fill hole, not the fluid pan, which is plastic and a poor conductor of heat, so it will usually measure a lower temperature than the fluid and cause an incorrect fill level.
I should also have mentioned that the original fluid pan screws have a T27 socket in the head that is prone to stripping. Also, the threads are prone to seize in the aluminum transmission due to galvanic corrosion. It can help to use a small wire-bristle brush and penetrant to clean all the exposed top ends of the screws above the transmission sump rim and apply more penetrant to the threads and allow to soak before you attempt to remove any screws. ZF revised the screws with heads that have T40 sockets which are much less prone to strip, and it is prudent to have at least a half dozen on hand, or better yet, a complete set. Sorry i forgot to look up the part number for the revised screws, but your ZF supplier will know.
I can't get a document to attach that gives the torque specification (10 Nm) and torque sequence for the pan screws. I'll try to attach it to a new message.
Also, before you drop the Mechatronic/valve body, note the position of the Park Position solenoid rod with the wye yoke. if you don't get it aligned properly when you reinstall the Mechatronic, you may not be able to shift the transmission out of Park into other gears. This illustration shows how the wye yoke engages the solenoid rod:
Yes, I remember this procedure from the X308, different gearbox, but I think the method is very similar. Again, I'm doing this on the lift so there's a much better chance of the car being level... thanks,.
Paul
@euphonium01 Paul, if transmission fluid has never been changed be prepared that drain plug will require very high torque to remove it. Have a long pipe, about 1-1.5m long ready to put over long end of the modified Allen wrench. BTW you will have to cut it per Don's B. instructions!
Two other things:
Steel screw in aluminum: get yourself a torque wrench I was impatient and started torqueing them by hand; I stripped two threads in transmission casing. Yes, new screws help, they are longer. I fixed threads with helicoils; that is an expensive fix, but I have luxury of having access to machine and all their tools.
The removing sleeve was straight forward to me, just like all instructional video say: reach over exhaust lines, disconnect connector, I used pry bar to get it turning then all went smooth. Removing sleeve, pull that tub at the bottom of transmission; reach behind exhaust lines wiggle sleeve, it will come out; same pry bar can help get it going.
Putting it in is a different story in my case I had to apply significant pressure to put sleeve in while pulling the locking tab. I summon help of wooden 2x4 about 20-25" long; wedge one end between transmission and propeller shaft coupling, middle of 2x4 touches sleeve and my hand at another end of 2x4; that gave me 2:1 advantage and sleeve just slit in place and the locking tab slid right back where it belongs.
One interesting fact: I was doing this on lift there is a step there::after you fill in first dose of ATF you need to get in a car, start engine. I did not lowered car all the way down; wheels were still off the ground. Car did not want to start, like immobilizer preventing. I lowered car to ground completely and then car started.
Good luck, it is not difficult job at all, just follow instructions Don posted in thread.
Do listen to Don and Big Koshka! They are not kidding either. I had to use a 2' cheater on the Allen wrench Don has pictured above (I also had to cut mine down to fit). It sounded like a rifle shot when it let loose and I could have sworn that I broke the Allen wrench! This applies to any ZF transmission. I have done a few MB cars and they are just as tight as the ones on Jaguars. Just something that ZF does from the factory I guess. Of course it does not help that the plug is inches away from a smoking hot exhaust system either!
I did pick up the special tool for removing this plug. And while it's not required at all it does make things a good bit easier! This is a knock off because as we know any JLR branded tool will be hundreds of dollars IF you can even find it! JLR 307-452. This one is a JTC-6878.
These are still around for about $50 or so.
If you want a laugh. Check out the JLR tool which is $475!! AND out of stock as well. JLR 307-452 Tool
ZF released some larger pan bolts and I install those when doing a fluid service. If you do strip a bolt out it's an easy fix. The pan is plastic and you will be replacing it. So you can break the plastic off around the pan bolts and use a Vise-Grip to spin them out.
One other thing is we have seemed to have lost a great ZF parts supplier as their website looks to have been taken down? Does anyone know what happened to the CTSC? The CTSC ZF Transmission Parts
.
.
.
Last edited by clubairth1; Feb 8, 2026 at 09:38 AM.
One other thing is we have seemed to have lost a great ZF parts supplier as their website looks to have been taken down? Does anyone know what happened to the CTSC? The CTSC ZF Transmission Parts
.
I just bought from them in December, the web site says "Account Suspended" so hopefully just some issue with the host or ISP.
Hi Big Koshka. Many thanks for your post. It’s not the first time doing this, I drained the ATF and fitted a new filter about a year/15 months ago, I used a new set of bolts that came with the filter and gasket.
It’s remarkably similar to the X308 I’ve done a few times, except the filter is internal and the old pan is used.
Paul
Many thanks for all comments and tips for doing this. I'm sorry its taken some time, but I didn't get the use of a lift after all, so had it up on stands and laid on a concrete floor. The British weather has been unkind so it was an as-and-when scenario.
However, with everyone's help and advice I managed to get the sleeve out, removed the valve block and replaced the four seals. I got it all back together with the connector being the hardest part to refit, it was just laid on my back and having little leverage to refit stuff. I fitted a new pan/filter with new bolts, torqued it down, and fitted a new sump bung that came with the kit.
I also followed the instructions for refilling, starting up and then topping up until it started to run out, refitted the bung and torqued that up too. Without doubt I would not have been able to complete the job properly without the help of everyone that chipped in, but in particular Don B who's advice and instructions were fabulous... thanks Don .
After startup I notice the 'Gearbox Fault' lit up on the readout, I switched off, left it 30 seconds and restarted... touch wood, the light hasn't come back on yet. Now, Im about to take her for a run and hopefully all will be Ok? I will report back after a good test drive.
Paul
That sounds like great news! Can't wait for your next update!
Cheers,
Don
So, mixed results with the test drive! At first, I had the same 'Gearbox Fault' message, the car would lurch forward and rev higher moving from 3rd to 4th gear. If it didn't change, it seems to stick in 3rd and won't go into 4th at all... then the fault message appears. If I switch off, then restart, the error has gone, select drive, then accellerate fast moving fast through the gears, it eventually drops in to 6th and I can cruise along no problem... that's the scenario I found at first!
However, after I accellerated fast it went up and down the box all the way to 6th, and after about 10 miles at 70 mph, it seemed to settle much better? The fault message didn't come back on even when I had slowed down to accommodate the country lanes/turns etc. to my home! Quite what cancels the error, by turning the engine off and restarting, I don't know. But it seems to clear faults and the car will go to 6th when accellerating hard, but brings the fault back on mostly when I'm having to go slow in 3rd and it's lurching as I accellerate towards 4th. Apparently the P0783 error code I get is a 3rd to 4th shift problem? If I start the car and clear the P0783 error, it doesn't come back unless I'm stuck at a slow speed as mentioned earlier. One article I read stated the shift area could be a malfuntioning Solenoid? I found this on the internet......
What does 3/4 shift malfunction mean? Summary. The powertrain control module will register a P0783 trouble code if the transmission is unable to complete the 3-4 upshift properly. Low transmission fluid levels, a faulty transmission shift solenoid, or a damaged transmission valve body can trigger a P0783 code.
All this started after I had starting problems with the bad earth lead, I had many warning lights come on including the Gearbox Fault message, all the others disappeared after I charged the battery and fixed the ground lead... but the Gearbox Fault is still an issue. If that tells a story on what has been damaged then please tell me. Ideas, advive, again, always welcomed, but I'm finding theres no consistency to the fault, so apologies if the description of the problem is unclear?
Paul
BTW, to Don B. The connector on the back of the gearbox was very wet with atf when I disconnected the cable, you were right. There was a good deal that ran out the back and the pins were wet with atf too. Obviously I cleaned it all as I refitted everything back and the sleeve doesn't appear to be leaking now.
Paul
The Sport Mode function is probably disabled due to the P0783 code. Here's the definition of the code, indicating that ths calculated slippage during the 3 - 4 shift is excessive:
I am also attaching a TSB I just found in my library regarding an updated transmission firmware version was released to address this specific range of codes.
My initial theory is that either your transmission adaptations have drifted, as mentioned in the TSB, and your TCM firmware needs to be updated, or the solenoid related to the 3-4 shift has become lazy, or the delay accumulator piston could be sticking. When you're accelerating quickly, perhaps it shifts quickly enough to satisfy the parameters in the TCM firmware, but when accelerating slowly, the shift is taking longer than the TCM considers correct and it is interpreting this as excessive slip and triggering the fault.
I can't remember if we have discussed updating the Mechatronic/TCM firmware using IDS or SDD?
I am also attaching a Sonnax manual with some detailed diagnostic information.
Was the sleeve changed? You can't just clean it out. The O-rings are the problem. Be aware that it's just not fluid in the connector. If not repaired in time the fluid will migrate back into the wires themselves under the insulation. Causing even more problems. I hope you put a new sleeve in.
.
.
.
it sounds like your voltage regulator or the engine control module isnt communicating right with the alternator which is classic for these jags since the charging is ecu controlled. those gearbox thumps and codes are almost certainly just a side effect of the low voltage freaking out the sensitive modules rather than a mechanical failure. check the small sense wires at the alternator plug for any corrosion and use your sdd software to look at the battery monitoring system data to see if it needs a reset.
I thought good luck finding a manual or user guide for sdd but then I thought, hang on I'm sure I downloaded something years ago. And lo I had 8 years ago apparently! The manual is 50meg so I'm not sure if it will attach, nope too big. Ah ah compressed it so the site should be happy now. Hope it helps a bit.
I thought good luck finding a manual or user guide for sdd but then I thought, hang on I'm sure I downloaded something years ago. And lo I had 8 years ago apparently! The manual is 50meg so I'm not sure if it will attach, nope too big. Ah ah compressed it so the site should be happy now. Hope it helps a bit.
Thank you so much JoeDredd, this is exactly what I hoped for but didn’t think it existed. This is a thank you from my phone, I will get online later today with an update on the gearbox fault for everyone.
Paul
.
