Please help me. My truck had a weird thumping sound only through the exhaust. It sounds as if it thumps once per revolution. I've asked around and have recieved many things. I've been told the harmonic balancer could be bad and throwing off the balance. Other said it could be a bad injector but I do not have smoking or lack of power or even a miss. Last I've been told it could be a valve train issue such as lifter, pushrods or valve/valve guide. The motor runs mint and doesn't shake or miss. Just has the thump through the exhaust. No lack of power what so ever. One thing that makes me believe is when I rev it in neutral it will shake on and off. The balancer is pretty wavy past the rubber. Please answer if you've had this issue. I'm replacing the balancer and pulls tomorrow. Thanks.

 

By this do you mean that the outer metal ring "wiggles or jiggles", such that it doesn't stay in the same place as it rotates? If so, good move on replacing it. The harmonic balancer on this engine is recommended to be replaced every 100,000 miles. It can and will break the crankshaft if it fails.

 

Did you resolve this question for the 6.5 there are actually (2) concerns on "snout end" of the crank, the balancer rubber allowing the weight to to move, and the accessory pulley rubber being bad that bolts to the front of the balancer.

 

The permanent fix for the balancer is the Fluidamper. leroydiesel.com has a good price on them