Heres the deal: I bought this M20 newly rebuilt by a GM dealership. They missed the front bearing support in the case being worn out, and the tranny came apart about a month later- everything was trashed except the gears. Had it rebuilt again. About a week later my truck was broken into, and they broke the tranny and shifter. Must have kicked it or somthing, because the iron shifting "arms" inside the cover plate on the side were both snapped. I replaced them and the tranny shifts awsome and works fine except for 4th gear when Im slowing down. It literally throws the shifter out of 4th gear into nuetral, but it still stays somewhat near in gear because then it makes a light grinding noise like the gears are just touching inside. Its done this in 3rd gear once or twice in the last few months also. What kind of damage am I looking at this time?

Maybe just a shifter adjusment will fix it, that's where I would start.

Your lucky you found a GM dealer that had someone who could fix the thing.

I have had several muncie transmissions with the same problem. However, for different reasons. One reason was because of very sloppy linkage. Felt like it was going into gear. In actuality, only partially. Therefore, jumped out on deceleration. Acceleration actually holds it into gear because of the angle of the gears.

The other reason, was because of what is commonly referred to as "dog ears". They are spring loaded "actuators" that the shift slider pushes the gears across, when putting the tranny into gear. That is what gives you the feeling of a slight bump when you go into each gear, and those "dog ears" hold the gear into place, until you shift across them again. Take the tranny out. Remove the side cover and visually inspect the shift collars, as you slide them in and out of gear. By rotating the shaft, you can inspect the gears and shaft. You will see what I am talking about. Good luck. Bob

You aren't using the truck 4spd bellhousing are you? That would explain your problem. A muncie bolts up but the register fit of the front bearing retainer doesn't match the bellhousing (the hole is bigger in the truck housing) so the trans isn't centered in the bellhousing. It will cause all sort of bad things to happen.

A worn our pilot bearing can also cause problems.

They missed the front bearing support in the case being worn out

I zoomed over this and after re-reading, this make no sense. There is no font bearing support. The front bearing fits in the case, a snap ring on the OD sets the depth, the oil slinger and a shim if added set the depth of the input and it's locked together by the gland nut and the front bearing retainer keeps if from walking out the front.

If the dummies over shimmed the input, left the snap ring off the 3/4 hub or used bolts that were to long in the front bearing retainer, death will set in.

Did Mr. GoodWrench stand behind the repair???

Mr. Goodwrench did not stand behind the repair seeing as I wasen't the one who paid for the rebuild [bought it from the guy right after it was built]
The bellhousing is a camaro unit. It has the same casting number as the sm465/truck bellhousing I pulled off. Im going to play with the linkage. It is a little sloopier then I'd like.

Question??

Will a Saginaw front pilot bearing sleeve casting bolt on to a Muncie?

I ask b/c IF it would, just rob one off a Sag. 3-speed and install on the Muncie so it will now center into a "big-hole", truck bellhousing.

I did this when I went from a 3-speed P/U Sag. to a 4-speed car Sag. tranny in my old P/U.

But have NO idea if cross-breading parts between the two trannies will work or not?? I figure they would tho b/c they both are used in the car bellhousing applications??????? (IF the four bolts line up??).......

pdq67

Question??

Will a Saginaw front pilot bearing sleeve casting bolt on to a Muncie?

I ask b/c IF it would, just rob one off a Sag. 3-speed and install on the Muncie so it will now center into a "big-hole", truck bellhousing.

I did this when I went from a 3-speed P/U Sag. to a 4-speed car Sag. tranny in my old P/U.

But have NO idea if cross-breading parts between the two trannies will work or not?? I figure they would tho b/c they both are used in the car bellhousing applications??????? (IF the four bolts line up??).......

pdq67

No. None of the parts swap.