My son has a 1988 700 R4 transmission in a '88 S-10 Blazer that broke, reverse quit working. He ordered and installed a B&M transmission rebuild kit along with a new torque converter but the problem still exists, no reverse! We took it out last weekend took it apart, reassembled it then installed it again and still no reverse. He did purchase a video for the rebuild but, there is nothing on there for trouble shooting. Where should we start looking for the problem or affending part?

Thanks,

ray....

 

How far deep was the tear down? It sounds like the reverse drum, or sun shell, is broken. This is the part that the aftermarket has retooled and dubbed "the beast." If this is not the problem, then you might check the front and rear planetary gears. I always replace these items during a rebuild. You never know when the teeth on the used gears are going to give.

 

The transmission was completely torn down and reassembled. There was no problems apparent to us during the tear down. All the teeth seemed to be in good shape as were the shells but, that is not from someone who really knows what is going on. We used a video that was purchased from Summit as a guide to rebuilding the transmission through this process.

ray....

 

If reverse is your only problem, it would mean either the low/reverse clutch is installed wrong (rotates the wrong direction), your lip seal is damaged on the low/reverse piston, or the shell is damaged. I would tear it down again, and triple check everything, make sure you air check everythig and then put it back together. I don't see the valve body being the problem but it wouldn't hurt to take it apart and make sure it is in the proper order and clean.

 

Thanks for your input, we are going to give it another try and tear it down to check those parts.

As far as the tear down, it was stripped completely. We used a B&M kit for assembly including clutches, etc. It is just a matter of our first try and we missed something, hopefully it is one of the items or over sights you mentioned.
Now I remember why I generally only have manual transmissions on my work bench; easier for me to follow the power flow and keep track of what is what!....

Thanks for your help.

Ray....