OT need help, 91 chevy pickup transmission

ericlb · Feb 25, 2012

i hope somebody on here works on these trucks, i have a good friend with a 91 chevy 1/2 ton pickup, v-8 and overdrive automatic transmission, the truck now will not go into reverse that is, it can be put into reverse, but the truck will not back up, all foward gears work, as i dont work on these newer vehicles, since i dont understand computers, does anybody know what i need to do for it, if it was an older one id change the fluid, filter and adjust the bands first, but im not sure this thing even has bands like the old vacuum trannys did, any help will be appreciated thanks, eric

504 · Feb 25, 2012

Replace or rebuild,changing the fluid and filter was 50,000 miles ago.

rankrank1 · Feb 25, 2012

GM did not go to computer control of the tranny until 1994. 1991 will still be vaccum control.

ShepFL · Feb 25, 2012

Check the shift solenoids. My 2000 K2500 trans. has now gone out for a 3rd time - GRRR.

Repair shop says they won"t go into a 3rd time. Working on fixing that position!!!!

Sprint 6 · Feb 25, 2012

Most likely the sun shell is broken. As others have said its time for a used one or rebuild what is there. Its not really that complicated of a trans if you keep it clean and watch what you are doing. You will need a few seal sizers and a piston spring compressor.

Allan in NE · Feb 25, 2012

Is it a half ton or 3/4? Tonner?

Allan

Allan in NE · Feb 25, 2012

If the fluid is full/not burnt and the filter is clear, the low-reverse clutch has had it.

Pull the dipstick and see if the oil is black.

Allan

LJD · Feb 25, 2012

Computer doesn't control any shifting in that trans (4L60 I assume). Computer/ECM only controls converter lockup via an RPM sensor, temp switch, clutch pressure switch and a vehicle speed sensor.

If your are sure 1st gear stills works and reverse does not - you've got a failure in the reverse input clutch assembly.

ericlb · Feb 26, 2012

thanks guys, im going to try to get him to either take it to a shop or at the very least buy a reman unit, while he is a friend, this time of year i just dont have enough free time to get into yet another involved type project, sounds like its time for a complete rebuild on that tranny, i could do a tranny swap in a day,[1/2 ton 2wd] if i can get him to buy one, i think its a case of he thinks i can 'just do something' and it will be ok again, from this it doesnt sound like it

Allan in NE · Feb 26, 2012

Nope,

Tell him it's gotta come down. There's no gettin' around it.

Allan

OT need help, 91 chevy pickup transmission

ericlb

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504

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rankrank1

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ShepFL

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Sprint 6

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Allan in NE

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Allan in NE

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LJD

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ericlb

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Allan in NE

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