chevydiesel

I have a newly rebuilt 700r4 the core came from a 89 astro van I'm using the tranny in a 1976 chevy pickup, it was working perfectly except I felt was running too hot (225 degrees cruising speed) because its running in a non-lockup torque converter application. To bump up the pressure and reduce slipping which is causing the heat buildup I replaced the servo with a corvette servo installed a 13 vane pump. Replaced the converter valve with one designed to increase fluid flow when using a non-lockup torque converter.

Tranny works great, runs around 180 degrees at cruising speed, good firm shifts with no slippage however, it now slips in reverse and reverse only. It will move the vehicle in reverse but if you gas it or try to back up an incline it slips. Before I did these mods it didn't slip in reverse.

I am puzzled Any suggestions.

FLT

iTrader: (1)

Personally I do not see a reason to run a non-lock set up unless you are trying to reduce rotational weight in the converter. For a street driven application a LU converter to me is a must. As for your issue with reverse I would suspect an issue in the reverse input drum or the low reverse clutch. Two clutches that normally do not have an issue unless there is a leak somewhere or something has been misassembled. Sounds like either way the unit will have to be gone through again. Vince

chevydiesel

Looks like I've got to go through it, I tried changing the servo back to the original servo thinking I might get lucky but no dice it still slips. Anyway thanks for your input.

Dyno paul

A stock early Atro Van, (Safari Van)Transmission Is calibrated for a 4.3 V6 and that was about 160hp, so that alone should have been modified to handle the V8 .Example. pressure reg spring , reverse boost, Throttle Boost valve, Governor , Servo, accumulator springs etc, Possibly the reverse boost valve was assembled upside down , possibly checkball capsole at teh bottom of the case is warn and the checkball went intro the case at the low /reverse piston area and stopped the piston from returning and this would make the clutches drag on until they failed. either way it has to come apart and properly diagnosed before reassembly.Also the band is used in secon and fourth, so changing the servo dropped your tempdown then it was slipping in fourth. PS as Vince said there is no reason to not have a lock-up converter