[piscator]

The transmission in my 2006 GMC Sierra failed while I was driving to visit my daughter at college. On the highway, two hours from home, cruise control set at 65+/-, the truck suddenly seemed to be stuck in 3rd gear and running at 4,000 RPM. I hadn’t even noticed the downshift.

I got off the highway, made it to a garage and checked the fluid level. It was down a quart. And it was leaking fluid. The mechanic came out and determined that I’d blown a transmission cooler hose. He said it would take a day to get the parts and replace the hoses. He gave me an estimate and I said go ahead.

I managed to rent a car, the next town over, and made it to my daughter’s in time for the music concert we were scheduled to attend. Weekend saved! (At great expense).

Saturday, I return the rental and pick up my truck. The transmission doesn’t leak, but it won’t shift higher than 3rd gear. The mechanic explained that what’s wrong is beyond his capability. So I proceeded home at 60mph/4,000RPM. Now I’m home, with a broken truck and a disassembled Porsche.

My reason for writing is simply to ask, “What do I do next?”

I’m a decent wrench but I know nothing about automatic transmissions. And if I wanted to work on it, it would have to be outside, because my shop is filled with disassembled SC Targa. I have friends at a local shop that I like and trust. I will ask their advice, but I’m hoping you guys can give me some parameters. Such as,

Does anyone have a clue what’s wrong with this transmission?

Does one rebuild an automatic transmission, or replace it?

And (inevitably) – Is this an opportunity to upgrade my transmission? Or install a stronger one? Six speed?

The truck is a 2006 GMC Sierra Crew Cab, 5.3 liter V8, and I really love it. I’m hoping to keep it forever. The engine is clean as a whistle. It has a fresh paint job. Brand new leather interior. And, I coated the frame with POR-15.

Any help in where to go with it from here, will be most appreciated!