When the truck is in park there is a noticeable vibration that pulses. It is not noticed when shifted to drive. I'm thinking a bad harmonic balancer. How can I inspect the existing harmonic balancer. What are the steps for replacement. I was searching for new ones online and noticed that there is a primary and secondary balancer, is there two? Any suggestions? All ideas are greatly appreciated.

Have you done a compression test?

Check the motor and tranny mounts, they will do the exact thing you describe.

Worst case, the crank broke and its running on a few less cylinders, :eek:

The manual trans ones sometimes came with a dual mass flywheel but you have a auto so you only have the one. Its easy to check, go look underneath, does it look like the out ring has moved from center?

If you have a slight air leak in the fuel system it will cause the symptoms you are describing.

Look real close at the rubber on the crank pulley. If it is bad it is pretty easy to replace.
Ted

You might have a look at the torque converter to flex-plate bolt area. If for some reason they worked their way loose it could also cause a vibration.
Don

Harmonic balancer.... especially if you get a brief "shake" when you shut it down!!!

The truck runs good and strong but just that weird vibration at idle. I think the crank is alright now but I will do some test and things soon. Thanks for all the ideas keep them coming, I will check the mounts and the balancer as suggested. I never performed a compression test on a diesel just gassers so I will check other possibilities first.

Going out on a limb here, but I think I have the same vibration.

1. Go out to the the back of your vehicle while it is idling and making the noise.

2. Press down on the top of your exhaust tip with the bottom of either shoe. If the noise ceases or dramatically decreases then you have what I have.

I believe there is a point where the exhaust mounts break down over time and are susceptible to a weird harmonic resonance vibration. When I press down on the pipe at the very tip, it's voila, quiet again. Maybe a crow bar underneath and start wedging.