Ok...so I've read several of the seemingly endless threads on the beloved (detested?) ZF 6HP26 - and boy do they ever get heated and contentious - but I have some questions that I have been unable to find a straightforward answer to elsewhere. Here's where I'm at: My transmission is acting a bit funny in some of the classic ways (jerks coming to a stop, slips a bit between 1-2 sometimes, and intermittently will exhibit what I can only describe as a pulsating growl when cruising between 45 and 60 MPH) and I'd like to address that before it eats itself. The car has 150k on the clock and has never (to the previous owner's recollection) had the transmission serviced at all. I plan to replace the pan/filter and have the system flushed and filled. My question is are there any other measures I should be directing the shop to take while the pan is off? Anything super important I am not doing? I have seen mention of some sleeves that should be replaced? I typically perform my own vehicle maintenance so I am unaccustomed to dealing with a shop. Just want to make sure I have all my bases covered.

 

The other part to replace during the gearbox service is the seal where the electric cables enter the gearbox.
Although not strictly part of the service, you might as well get it done. All the reports on this job that I've read say get this done.
The specialists who did my gearbox service last year also did a reboot of the gearbox computer. So the memory is wiped and
the learning can start over again. Although my service was done at around 70k miles it was not a 100% cure. However it did take
out the horrible lurches when coming to a standstill or pulling off at low speed while moving. There is still a slight jump on 5th to 6th but nothing major.

 

After those parts changes I'd make sure it has the latest software (in PCM & TCM). That will also clear the adaptations if they're changed but if they're already up to date then have the (TCM) adaptations cleared.

BUT BEFORE YOU DO ANYTHING: check you have no codes other than a pending P1111 and then check the fuel trims are OK. You do NOT want to be making any changes if they're not.

 

Thanks so much! I prefer to do things right the first time so I want to make sure I'm not missing anything. I've checked the codes and there are no trouble codes showing. What should the fuel trims read and if they are off what would be the next step?
Also I have noticed two other things. If I need to start a separate thread for them I will, but I thought I would mention them here as they could potentially be transmission related (unlikely, but possible). Sometimes under acceleration the traction control kicks in at times when it does not seem like it should (very light acceleration on dry pavement) and at times under heavy acceleration there is a clicking noise that seems to come from the left side of the engine bay (think baseball card stuck in bicycle spokes type of sound). I know the car has a tremendous amount of torque, but the TC is stepping in at times when the tires show no signs of breaking loose and I wonder if it could be a sensor or if there is some common reason why this happens. With regard to the ticking I only notice it under fairly hard acceleration and it increases in speed along with the engine, but I am at a loss for what may be causing it. I will try to replicate it with the car in park so I can better localize where it is coming from.

 

Check the engine mounts to see if the engine is moving under load. Sometimes the 'clicking' noise can be caused by the torque converter.

Replace the electrical connector sleeve at the same time the gearbox is being serviced as it can only be removed after the pan is removed.

Above is the torque sequence for the pan bolts. Attached is the correct procedure for checking the gearbox fluid level.