1996 4L80E transmission slipping

[Sled Idaho]

1996 GMC K2500, 4.10 limited slip, 4L80E 4-speed auto, 5.7L Vortec, all stock (no chip or programmer).

Coming over Horseshoe Bend Hill from McCall to Boise on Sunday, maybe 5-6% grade, I first smelled something getting hot. This is after maybe ten minutes of climbing the hill at 2800 RPM. About three minutes after the smell started the transmission began to slip. I shifted back into overdrive to finish the drive to the top and stopped. The smell was pretty strong, especially on the passenger side under the hood. I let the truck sit for about 5 minutes and then continued home. Since then there have been no problems, but I have not put any kind of a prolonged load on the transmission either.

I do not have the skills to do any of this myself. It is currently in the shop that I have taken the truck to for 7-8 years. The guy was afraid to flush it because it "might finish the transmission off." How do I know it's the something like the torque converter, wire harness, etc. that is bad vs. a bad transmission that needs to be replaced? A replacement will cost over $3K so I want to make damn sure it is the transmission and not some other part.

Thanks in advance.

 

[Fosgate]

Probably got the fluid a bit hot. Not uncommon to get snow, ice buildup on the front of the vehicle keeping the air from circulating over the cooler (or on the cooler). What do you have to loose at this point by doing a $150-200 flush vs. new trans? Not that I want to advise this but if it were me I'd flush it and take it to another dealership to trade it. (like no one does this.)

 

[brushwolf]

Flush it before the burnt fluid finishes it off for you. Number one killer of transmissions is bad fluid.

Flushing it will not kill the transmission, If it dies after a flush it was dead anyway.

 

[800switch]

Change the filter
Flushing it will only make the fluid better.
If any damage has been done the particles will build up on the filter, plug it up, starve the pump and the low line pressure will take out the rest of the clutches
80's are prone to filter plugging

 

[oonighttrain]

1996 GMC K2500, 4.10 limited slip, 4L80E 4-speed auto, 5.7L Vortec, all stock (no chip or programmer).

A replacement will cost over $3K so I want to make damn sure it is the transmission and not some other part.

Thanks in advance.

$3k??? did they grease it up before they tried to jam it in?

pm troy (switchback) he will give you the name of a website for good used parts... i found a trans for a friend of mine in montana. got it shipped in from alaska for a 3rd the cost of what the repair shop was saying..

 

[svensdream]

those trannys are natorious for going out. I also know that hill, it's a biggin! I drove it every day, I've seen alot of dead cars on that hill. A good way to prolong the life of that tranny is to only run it in o/d when your at highway speed low load and never when towing, because it likes to shift a lot and it wears it out quicker. I would have it flushed and hope for the best.

 

[Sled Idaho]

Thanks for the input everyone. I did get it flushed figuring that if it was going to die, the shop was the best place for that to happen.

Staying out of OD when towing is something that I will begin to do. The truck has 4.10 gears and it is usually only my open two-place with two sleds that gets towed. The truck rarely downshifts when cruising on flat terrain and towing, but I now understand that this situation is quite hard on transmissions even though it does not appear to be at the time.

So far so good. Shifting is actually a little stronger on regular highways. I haven't attempted Horseshoe Bend Hill again but plan to tomorrow afternoon. A transmission shop was called by the mechanic while they had the truck in on Wednesday. He mentioned that the transmission may have gotten hot, and vented some of the fluid onto the exhaust manifold. That would explain the smell coming from the passenger side under the hood. The guy mentioned that the amount is usually quite substantial and that the fluid level should have read low, which it did not appear to.

Thanks again all.