Originally Posted by hahnmgh63

545moose, the stepper motor and fault you are talking about is for the Transfercase, bolted onto the back of the transmission. A common failure. Best thing to do is to cycle it at least once a month or they go bad. The forum poster, Crozzer is talking about the motor to engage/disengage the rear end diff which is a rare option on 955/957's, as he mentioned, 1Y1 option, very few have this option. It was available separately as option 1Y1 but also came with an off-road package but not to be confused with the off-road Nav package which just gave the bread crumb trail in the Nav system activated.

Originally Posted by Crozzer

Anybody know if swapping this thing will drain the fluid and require a refill? (Not finding it in alldata…)

Thanks!


EDIT: of course I find it right after posting. Says to be prepared for minor fluid leaks. Doesn’t appear to require fluid change.

Originally Posted by Crozzer

Almost. That one is a B. The last letter is the revision. That was a rear transverse lock control module, not a transfer case module. Apologies for the confusion.

Originally Posted by hahnmgh63

There is a TSB "Technical Information Service 3 19/10 EN 3978" for all 955/957's, “All-wheel drive system defective”, it tells you to change both for a low range overheating problem of the stepper motor. Some do both anyway or try to find a later control module if they have an early '03~'05 955 as there were later program/module revisions.