Isx 870 with 1.2 million miles 05 international

[Waterloo]

Agree with Squish, the rpm's need to be up. I have an 18 speed, and run mine in low 8th to keep the rpm's at a steady 1700, I have the 3:42 gears and have found this to be the best solution for the so so gearing in my truck.

Also, this is on a fresh in frame, and the motor loves it, she is finally breaking in as I have been able to do some cross country trucking along with running through a few mountain ranges. Running these motors at or under 1400 rpms and you are just asking for trouble as Squish stated.