GM Sierra Auto Tranny Pop and Scream

Maintenance/Repairs
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1

Hello,



My husband and I are having a problem with our 95 GMC Sierra 2500 4x4 truck. It has about 150k miles on it and we’ve had it for less than 2 years.



Here’s the story:



We were getting on the freeway and as soon as I stepped on it to accelerate it onto the freeway, it popped and started making this loud whirring noise. We also lost acceleration at that point. I immediately pulled over to the side of the road. We didn’t have any warning prior to the failure. It was like something broke or let go all of a sudden. We immediately thought tranny trouble. There was no smoke or fluid leaks in evidence, the drivetrain feels solid and we checked the fluid and it’s bright red and free of debris.



My husband got in the truck and tried a little shifting, and it just screams when you put it in reverse. The engine sounds fine, this noise is coming from behind the engine under the truck. In drive, it will roll forward but any more than 2mph and it starts to make this oscillating whirring noise.



We had it towed to our house and are calling our mechanic in the morning, but until then, what do you guys, and gals, think? I like to approach a mechanic with a little knowledge to go off of.



Thanks in advance for your insight.



Harlow

2

Thats classic sun shell failure, a very common problem in the 4L60E where the collar of the sun shell breaks where it attaches to the sun gear. The noise you are hearing is the sun shell scraping the inside of the transmission case along with the broken collar of the sun shell scraping the shell itself where it separated. You are looking at an overhaul.

Here is a pic of a broken sun shell. You can see the broken collar still attached to the splines of the sun gear.

transman

3

Wow! That sounds crappy!! Thanks, Transman, for the response. We might just head to the junkyard for a used tranny to replace it with, unless we can get an overhaul we can afford with a warranty. Wow, that sucks. Thanks again.

I’m still open to second opinions, but you sound pretty convincing.

4

Do one thing for me. Somebody needs to crawl up under the truck… Count the bolts holding the transmission pan on. The 2500 series used 2 different transmissions, a 4L60E and a 4L80E. You are going to find either 16 or 17 bolts holding the pan on. How many bolts are holding your transmission pan on??

transman