Hello Scotty! I have just bought 06 Chevy Tahoe that was one owner and had about 170k miles. I drove it on the highway for about 2 hours back home and it was just fine until I hit some mountain roads the last 30 miles of my trip back. When I started going uphill the engine started to rev high but no acceleration. Its a 5.3l ls. The truck itself seems in good shape. I was told by previous owner it sat for months sometimes. Please help!
On vehicles with that many miles when you get in a situation like that it’s comparible to towing a trailer on a flat road. Sounds like the transmission wanted to downshift but was struggling to do so. I would recommend trying it again on same type of roads but putting it in tow-haul mode/turning overdrive off. Many years ago I had a mid 80s F150 , on a trip through Pennsylvania to Ohio even with the small V8 at 80k miles I had to turn my overdrive off at times keep it from struggling. If it runs fine other times I doubt anything is wrong. Good luck. Let us know how it goes.
