(10-27-2017 )Waterloo Wrote:  I had a similar thing going on, felt like my driveline or something similar, was worse when pulling a hill. I took the truck to the shop to have the driveline checked out, and I had them throw their computer on the truck to check out an in cab issue I was having. They ran Insite and DiamondLogic, ProStar, and it showed five hits on the Cam Shaft Positioning sensor and a bad dimmer switch in the cab. So, I replaced the Cam Shaft Positioning Sensor, paid $27 for it at the corner Cummins shop, not knowing that this was actually causing my vibration issue. Surprised the hell out of me, LOL!

I then went and replaced the Crankshaft Positioning Sensor for good measure. They are both the same part. Cost is around $25-$60 ea., depending on where you buy. The part # is 4921599

Only use a Genuine Cummins Part. This part is to important to go with some Chinese knock off.

Here is what it looks like... https://puredieselpower.com/class-8-products/cummins-isx-crank-cam-position-sensor-4921599.html

If this is your issue, they are both located on the driver side of the motor. The Cam sensor is in the head, just forward of the Jake Brake harness.

The Crankshaft Sensor is down by the damper, you may have to remove one of the radiator braces to get to it. Here is my thread regarding removing that one, with photos, very good reference. http://rawze.com/forums/showthread.php?tid=2249

You will need a 10mm socket to remove, and universal joint with an extension to get to the Crankshaft Sensor. it will pull out with a few wiggles once the 10mm bolt is removed. When you put the knew one in, make sure to use gear or engine oil on the o-ring located on the sensor. The Crankshaft sensor needed to be turned and pushed in and it then locked itself in. Make sure that they are seated properly or you will have an oily mess on your hands.

I cannot say that this is your issue, but it sure sounds familiar. And, Winter is coming on, may be a good idea to just change them out. It is a vital sensor.