Rebuilt 700r4 - no reverse
Hi. I just rebuilt a 91 700R4 with the TCI kit, and installed a B&M RV heavy duty shift kit. I carefully followed B&M's instructions for check ball placement.
I installed the transmission today and don't have reverse. I do have forward gears but they seem very weak. I can step on it with my truck in low range and still hold it, with the brakes, and my brakes are BAD.
There doesn't seem to be any engagement in reverse at all
This is my first automatic, and first time rebuilding one, and I don't even know where to start. Any ideas before I go searching for a new transmission?
Have you adjusted the TV cable properly? Is the trans fluid level up to spec?
your first rebuild?
sounds like serious pressure loss.
The B&M shift improver kit may have listed the check ball locations incorrectly or you looked at the wrong year for your application?
TV cable would not affect reverse since line pressure is raised by the low/reverse boost valve.
there are many things that could be wrong.
Check the assembly of the boost valves... often the DIY folks install them backwards or miss the snap ring groove .... then the boost valves blow out of the bore
Trans fluid was a little over filled but I dont see how that will cause me not to have reverse all together.
I checked the number stamped in the case and it is indeed a 91 transmission (according to the haynes manual). Came out of a 91 Astro AWD. I spent a lot of time double checking all the chek ball placments, and everything added up in the end.. with all the check balls in place, I had 2 left over, as B&M said to leave out 2.
Please refresh my memory, where are the boost valves located?
There is one valve on the pump retained by the snap ring, which I had to remove and replace the spring with a B&M piece. I had a hell of a time getting the snap ring to seat properly. Is this the boost valve?
One more thing, I did partially disassemble the pump for cleaning. ONce i had the 2 halves apart I removed whatever i could that wasn't reained with snap rings or clips, is there anything I could have installed backwards? I didn't use a alignment band to put the pump back together, I eyeballed it. The pump installed in the case effortlessly, so it has to be close. Is it critical that the 2 pump halves are aligned perfectly?
there are two separate boost valves in the same bore in the pump of this 1991 4L60. They are about the same size , different designs though.
the PR valve goes in first , then the PR spring , then the low / reverse boost valve , then the main boost valve , then the snap ring. If these are not installed correctly the pressure will not be correct
thanks for the help. Dropped the pan today and found the valved popped out. I accidentally installed the snap ring into the little machined bevel in the bore, not in the snap ring groove. And to think i actually fought with that for a good 20 minutes trying to get it seat into no groove. Fixed it and works great now thanks
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