Continuous Problems with this tranny/truck. Have been chasing bad gas mileage problems as mileage was inconsistent. Also gutless no take-off and no pull for even a light all aluminum enclosed double snowmobile trailer. 5.9/360 with 3.55 gears.
First, changed torque converter as failed lock-up test at dealer. This got my gas mileage back to where it used to be for about a month. Went back to dealer and engine would only pass lock-up test sometimes. Torque converter changed again. Mileage again improved. Tranny shudder and overheat problems on a long trip with trailer. Changed entire tranny and torque converter in January with new tranny and rebuilt torque converter. 3/4 overdrive cluthes and torque converter gone again in May rebuilt entire tranny and replaced torque converter. Strangely the overdrive did not work for about the first tank of gas as the rpms were about 2100 for 60mph. Then all was well as rpms were 1700 at 60mph. Went to dealer to have lock-up test done after a week and to see all was well. Failed test sometimes. Now it's been about 3 weeks and it won't stall on the dealer lock up test and the fluid seems to have fine grey/black particles through it? Any ideas as to what to do? Still mobile for now! Please hurry!

Wow... that is an extremely long list of problems. I would get a brand new transmission and a brand new torque converter put in and if i had problems with it again, get rid of the truck.

I think you need to see a different dealer. This is totally odd this many times. Someone who is working on your truck is obviously handicapped by their own lack of proper or enough education.

Yes, the transmission will break.
Yes, it can be fixed.
Yes, I believe you are in the process of being had.

What about the TCU updates? were they performed?

The truck had an update when I first got it about a year and a half ago. I had complained to them about lack of power and pinging.

I was at the tranny shop today and the guy figures it has to do with the stock switch valve for the torque converter. This is a link to the part he figures may solve this torque eating monster, although the problem has occured in more than one transmission in this truck. (Currently on the fifth torque converter).

This is a link to the part he figures may repair this torque eating monster:
http://www.transmichigan.com/catalog/product_info.php?products_id=291


???

I'm going to check on the updates in the next couple of days.

Along with that Sonnax valve, have them install a Transgo TFOD-HD2 and go a little on the mild side. Most dealers don't use these aftermarket parts. Its too bad, these little aftermarket parts really do wonders.

With burnt fluid, parts are tearing themselves up.