What's wrong with my automatic transmission?

I have a 1992 GMC Sierra, half ton, 4 WD with a 5.7 motor and automatic transmission. It has 140K miles on it.

Earlier this year it felt like it was slipping in reverse. It got to the point where it would barely reverse at all. When it would reverse, it was really slow. I could mash the gas but it would just barely go....if it would go at all. I had the fluid changed and added an automatic transmission restorer. It didn't change anything.

One day it just wouldn't go, and I had it in a spot where it was stuck and I had no room to get my other truck behind it to pull it. It was facing downhill a bit and me and a buddy couldn't even push it. I got mad and put it in reverse and mashed the gas for several seconds. It started going.....faster and faster until it was reversing at top speed. For several months after that it worked completely fine.....like new. But now it's starting to do the slow reverse thing again.

Does anyone have an idea of what it could be. I don't want to put another transmission in it if it could be a simpler fix.

Thanks, in advance, for your time.

falconry22019-11-18T16:11:20Z

There are multiple known issues with the 4L60 and 4L80 transmissions, besides normal wear and tear (every auto transmission is going to wear out clutch packages) they have tendencies to break shell gears, and other parts. One thing to be aware of is that the aftermarket has caught up with many of the factory weak links and you can rebuild a transmission that is almost bullet-proof. If the truck is in good shape it certainly is worth a rebuild, and if you can pull the unit yourself that can save a little. 
Not everyone should endeavor to work on trannys but the GM units aren't difficult to work with. Do some research on common 4L failures then call around for a build price, that way you know what you're paying for. Most of the "hard" parts other than the shell can be reused, but some could be upgraded if you and the shop agree on what works best.  

10

bo2019-11-18T02:16:36Z

transmission shot. fluid and filter change is a maintenance procedure not a repair. find local shop at ATRA.COM for more help

10

Pearl L2019-11-18T01:57:50Z

you need to have a mechanic check it out

02

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