Hi all,

I've got a 2001 Sierra 1500 4X4, originally with a 4.8, now a 6.0.

I've killed 4 transmissions. All 4 were used units, none with over 25000 miles. Two were left stock, one modified with a Vette & Sonnax Superhold servo, and the 4th with a full transgo HD-2 kit + Vette & Sonnax servos. All times the converter was swapped with different units and the cooler flushed. I monitor temps with a AeroTech scan gauge and have never seen a temperature over 160'F; nor have I ever read a code or had a MIL light. Failures occured with both a stock tune and two different tunes from Wait4Me, 3 failures were with the 4.8, this last one was behind the 6.0.

All failures occur while highway driving with a 'false neutral' whenever in D or 3; manual 2 and 1 work great.

I beat on the truck, I've always expected a sunshell or some other failure, but it's been my least abused point that fails.



I'm at a loss with this one; am I looking at a chassis electrical problem here? Thoughts? Things to track down?

I don't want to drop the money on a FLT if I'm just going to kill it again from some strange problem.



Thanks,

Paul

 

lol, you keep burning up STOCK transmissions, so you replace it with another STOCK transmission???? The factory 3-4 clutch pack is weak, very weak. Get yourself a good BUILT transmission with a good 3-4 setup, lol I don't think you have a "chassis electrical problem".

 

Give Vince a call, your engine will go out before you break their level 5.

 

What a helpful post! I guess I'm nuts for hoping that a stock transmission might hold up behind a stock powertrain!

 

I had a slip in 2nd once that hurt my original transmission. I think it was electrical. Couple days later started getting misfires and found a plug wire laying against a header and had been arcing. Fixed that and its never done it again

 

Do 4l80 and be done with it. My FLT level 5 is holding up fine with a T76 turbo and awd launches. It started slipping a little and I had it serviced changed fluid and filter and bam back to like new. But when I kill it it will be a 4l80 from FLT.

 

I wouldn't consider a 4.8 to a 6.0 swap stock, nor did you ever say it was stock. If you did a motor swap I would think it was modded.

 

I'm planning a FLT, at least a level 4. Knowing that I've toasted a mess of stock ones doesn't exactly make me comfortable putting it in if there's an underlying, non-trans, problem.

Keep ideas coming if you have any. A local shop wants me to check on the G110 ground condition.

 

Wondering about temperature in your part of the country. Is there any chance you aren't getting fluid flow to the rear pack in the severe cold?

 

It's a possibility? Every failure has been in the winter. I have been using Chevron Dextron VI since it hit the market.