Reverse band?

[msega]

My 1991 420SEL's reverse doesn't work anymore. The only thing that happens is the car very slowly rolls backwards, but only if it's reversing down an incline. The car can freely rev in reverse, and may even grab the gear for a second, but quickly looses it and is back to a sort of neutral mode.

I've read about a reverse band adjustment, but I don't think this car has one because we cannot find it. So the plan is to take the transmission out and replace that band. The transmission is perfect in every other gear, and you can barely feel the shifts.

Does anyone have a sort of diagram for the transmission?

Anything else to change out while the whole transmission is out? We plan on changing the front and rear seals while its out.

Any help is appreciated.