2005 Suburban 2500, 4x4, 8.1, LT, 60k miles... Around town, no problem... drives fine... About a month ago, started hearing a 'buzzing' from undercarriage. Sounded a lot like a loose heat shield on muffler, so I disregarded for the time...
Last week hitched up for an extended trip east... 20 minutes on secondary roads under 45mph was fine... but after getting on freeway, and cruising at 65mph (speed control), truck started to 'buck', then RPM's spun freely up to redline... I switched off cruise, and coasted for 4-5 seconds, then gassed it, but engine reved like it was in neutral... shifted into 'N', then back to 'D', tranny seemed to engage OK... 55mph to the next exit about 5 minutes up... drove home... again, no problems on secondary roads...
My mechanic looked at it... said it sounded like clutch plates were gone... swapped out remanufactured tranny. Brought home... hitched up... drove secondary roads- no problem... no rattle... get on highway- same thing... identical problem... buck... buck... reevvvvvvvv...
Mechanic is stupefied.
Is my trust in my mechanic misplaced?
Could there be a tranny 'computer' problem?
Anybody??