I have done about 400 miles on my 2004 x350 since I changed out the transmission pan, seals and fluid. Prior to this work, I had seen the P0829 (gear load 5/6) message accompanied by restricted gear changes several times. My old fluid was dirty but no evidence of swarf on the magnets and the "goggle" seal and 4 "tube" seals were in good condition. Since the work was completed, I have seen the error 3 times and every time was after I had flipped the sport mode switch while driving. Since I drew this conclusion I have driven the car from standing in either normal mode or Sport mode for at least 300 miles without the problem coming back.

In every other respect, the car drives perfectly I can see how flipping into or out of Sport could cause the pressure drop/increase to create the problem but wondered if anyone else has drawn a similar conclusion or has any further suggestions to track the problem down. I had planned to get my local independent dealer to re-load the transmission firmware until he told me there was no such procedure - I wont be going back there. My nearest Jag dealer is over 50 miles away so I will need to plan the appointment.
Steve

 

You mention you replaced "seals"...does that include the mechatronic sleeve?

 

Yep - the Mechatronic seal is the one I called "goggles", I also replaced the sleeve seals (4) and the TCM plug seal
Steve

 

So I mailed the ZF support desk. They were very quick to respond and asked a number of questions - How much fluid did I get in after changing the pan, what did the old fluid look like, did transmission go into failsafe etc. Based upon my responses they suggested changing out the pressure regulators as a set but pointed specifically at EDS3 which energizes for both second and 6th gear and further warned that I should stop the car immediately if the transmission ever goes into failsafe as burnout of the E3 drum could be immediate !!

For now, I continue to find that if I engage or disengage the sport button only at startup and when the car is in Park - not on the fly - I do not experience any problems, Hope this helps somebody else

Steve