Worms Shafts may Need Thrust Washers Removed:
We recently checked out an ABA set of InterMountain F units with Quantum QSI sound installed. At very low speed 1-10 smph, the locos exibited the “herky jerkies”. Generally most quality diesels run pretty smooth. Also, because QSI’s BEMF and Regulated Throttle Control (RTC) actually work to smooth out rough running, we became suspicious that there were mechanical issues.
Our techs disassembled the locos and determined that the worm shaft thrust washers were creating the interference. We removed one from each shaft and the locos now creep as they should.
There is no way to tell how many InterMountain F units may be affected but if yours is a little “herky jerkie” at low speed then the thrust washers may be the problem!