Well, Thursday night my mom's car (93 400E) lost reverse but only reverse, all forward gears shift as good as they always have.. she got home, parked the car. everything was normal seeming.. till the next time she tried to back out of the driveway. when you put it in reverse. its not like its in neutral.. it actually tries to pull a very small amount.. but it seems to go backwards and then forwards. i checked the fluid of course and it was clean and topped off (had just been changed along with the pan, gasket, filter). i dont have much experience with transmissions. ive replaced valve body gaskets, governor rings and things like that.. but i looked at the breakdown of this transmission and i didnt see just a reverse servo that may be sticking. can anybody offer some advice please? any help is appreciated.

 

You also have a 722.3 transmission. What has happened is that your B3 reverse clutch has worn out. This transmission is unique in the way it gets reverse, having its own separate multi-disk clutch that engages between the case and the main planetary carrier. Therefore, it would make sense that when you put it in reverse, the clutch might grab a little, but then slip, which would then cause you to move forwards instead of reverse. The only way to fix this is to replace the B3 clutch disks, so basically you need a rebuild.

However, you can replace these without a full rebuild if you want to give it a shot. Drain your fluid and torque converter, remove the transmission from the vehicle. It's actually quite simple after the transmission is out. Just remove the front pump cover (The very front where the torque converter attaches to.) After the pump has been removed, you will see the K1 clutch drum and underneath it is the planetary gears. Just remove the k1 drum by gently pulling up. You will then see the B3 clutch disks around the perimeter of the case. I think there are about 3 or 4 of them. You should be able to order them online. wittrans.com is where i use. Also, don't forget to scuff up the steel disks with a little sandpaper before you reinstall them. This lets them grip better by providing a surface to retain oil molecules. Yours will probably be very burnt and dark looking, so sand away.

Good Luck!

 

By the way, when you changed the fluid previously, was the old fluid very dark and filter all sludged up? Often many vehicles transmission fluid has never been or very rarely been changed. In these cases, it is sometimes possible for a clutch or band to be very badly worn, but since the fluid is so saturated with particles and worn friction material, it acutally provides grip for the worn clutch members. When you change the fluid, there is no longer enough grip for the worn components. I would do a rebuild, but I have also limped along many a worn transmission by adding a bottle or two of Lucas transmission fix. It's worth a try as a short term solution.