nofoolin wrote:
As a follow up, I had an '03 lby tuned at 400 hp that I ran for 12 years with no real issues except injectors, as the lby's are known for.
Most freeways and many highways post the grades as you are probably aware of. For 6 and 7% grades, I would shift out of overdrive before the hill/grade with light stress on the tranny. Kept it in direct drive (5spd) running about 2500 rpm (65mph) for the entire hill, a little slower on the downgrade. Shifted back into overdrive for the flats and smaller hills. Very few shifts during the day, always under light throttle, torque converter locked, never a tranny problem.
Have pulled on and off for 40 years. Lots and lots of miles. Treat it right and you'll find they are very stout.
Good bringing up that info of shifting out of OD BEFORE the hill. I make it a habit but my mind wondered last year and I didn't. Don't know if I confused the computer or it was the degree of the hill or what ever but the tranny started shifting back in forth the speed of lightning. Thought the tranny was going to come through the floor! Good thing it's an Allison, didn't seem to hurt anything.