I have a Thomas 1991 school bus (36K gvwr) with a CAT 3116 engine and an Allison MT 643 transmission. I purchased it quite recently and when driving it on the highway, the engine RPMs are at 4000 driving at 55mph.
I don't believe the transmission has an overdrive gear, but the rpms seem like a lot to a newbie like me. In fact, 4000 rpm is the furthest possible point on the tachometer.
- is this harmful to the engine?
- is this normal?