Th350 question

Glad you got that figured out.

Instead of starting a new thread figured I'd add my questions/issues to this one. In-laws have a trash truck that is a 1994 GMC Sierra 1500, 2wd. Motor has 286k miles, trans has been replaced 3 times over the years, each time with a stock TH350. Current trans has around 50k miles in it now and was last replaced 9ish years ago. Truck probably gets driven 800-1000 miles a year.

Wife's uncle drove it the other day and said it didn't feel right so parked it at the In-laws. I checked the trans fluid first and it showed full and no smells outside if normal trans fluid smell. I drove it that night and Overdrive and Drive were slipping like a mofo. No issues driving it in 1-2-3, but nothing in D or OD.

First time I've ever had a trans slipping like that, so not sure what is going on. Any ideas or things to check or time for another transmission?

Youre describing a 700r4/4L60, not a TH350. And one of the most common failure modes of a 700r4 is burnt 4th gear clutches, towing any sizeable weight in OD is a big nono and usually results in this condition, also big tires, hard usage, normal wear, etc. Pretty much a normal occurence with these transmissions and the reason they have such a bad reputation. Most likely its time for trans number 4.

d_daffron said:

Youre describing a 700r4/4L60, not a TH350. And one of the most common failure modes of a 700r4 is burnt 4th gear clutches, towing any sizeable weight in OD is a big nono and usually results in this condition, also big tires, hard usage, normal wear, etc. Pretty much a normal occurence with these transmissions and the reason they have such a bad reputation. Most likely its time for trans number 4.

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Interesting. I figured the trans was a TH350 since that's what her Uncle had said, and the truck has been in the family for 15+ years, but I'll need to crawl under the truck to verify now. It's a 2wd that was used as a DD so heaviest load hauled has been a drop trailer and lawn mower.

A 1994 half ton chevy came from the factory with a 700r4. Also a TH350 is a 3 speed trans so if the trans ever had overdrive then it can't be a TH350.

And unfortunately broken sun shells from not coming to a complete stop between forward and reverse and lost 4th gear due to a poor clutch design are very common in these trucks.

d_daffron said:

A 1994 half ton chevy came from the factory with a 700r4. Also a TH350 is a 3 speed trans so if the trans ever had overdrive then it can't be a TH350.

And unfortunately broken sun shells from not coming to a complete stop between forward and reverse and lost 4th gear due to a poor clutch design are very common in these trucks.

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Good to know on 700r4. Guess the incorrect ID on the trans is why her Uncle is a Ford guy instead of a GM guy.

d_daffron said:

Youre describing a 700r4/4L60, not a TH350. And one of the most common failure modes of a 700r4 is burnt 4th gear clutches, towing any sizeable weight in OD is a big nono and usually results in this condition, also big tires, hard usage, normal wear, etc. Pretty much a normal occurence with these transmissions and the reason they have such a bad reputation. Most likely its time for trans number 4.

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Depending on the year model, GM did make a Th350 with Lock-up.(OD) These trans were garbage! Actually had an electrical harness for the lockup.

jayphizzle said:

Depending on the year model, GM did make a Th350 with Lock-up.(OD) These trans were garbage! Actually had an electrical harness for the lockup.

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That's a 350c. Electronic convertor lock up but still only has 3 gears. No od. If you ever run across one buy it. Corvette guys will suck a golf ball through a garden hose for one last time I checked.in 94 I'm gonna say 700. Should look like a 350 but have a square electrical plug