Engine/Transmission (1998.5 - 2002) tramsmission slipping @ 285000 klms,torque issue?

[GreggNoble]

hi, when i`m just chuggin along about 80klms and my truck is in high gear and torque locked engine reving apx 1400 rpms if i then give it a shot of fuel the engine will rev but the truck doesn`t speed up , also even if i`m driving faster and i hit a bump in the highway the engine will rev up for a second and come back to normal after the bump. Whats strange is that as long as the highway is smooth and no matter how steep the hill the slipping wont happen

after 285000klms is that how long these trans last anyhow? thanks