6.2l Diesel Bad Vibration at Idle

[marknelon]

Hi there, I have a 1983 K10 with a 6.2 and a 700r4. I recently did an oil change and replaced the worn out bushing mounts for the transmission/ transfer case. I started it up when I was done and after it warmed up I noticed a bad vibration shaking the entire truck. When I press the accelerator it smooths and I notice no bad vibration. This happens in drive,park,neutral, and reverse. I have checked/replaced the following:

1. Obvious culprit the harmonic balancer, I replaced this with an AC Delco April 2019, the rubber is bulged out about a little bit, but I see no cracks or other obvious failures.
2. Checked Injector, PO replaced them about 13K miles ago. Cracked each line at injector and engine stumbled on each one.
3. No metal or any contaminants in the old oil, I change it about every 5K miles.
4. All pulleys appear to be straight no wobble when running.
5. Transmission has fluid and shows no signs of damage.

What else should I check? I have a new balancer on order just in case, but I don't know where else to look. I've talked with a transmission shop, and he doesn't think it's the transmission because it goes away when accelerating.
Thanks for reading hopefully one of you can help me solve this problem.

[JohnC]

Did the problem start when you changed the mounts?

[marknelon]

Yes, right after.

[trbankii]

You changed the trans/t-case mounts. Have you looked at the engine mounts?

[jhindman]

Did you figure it out??

I have a very similar problem. Changed balancer no help. Also vibration seems to get worse as motor warms up. I have not Changed any mounts.

[Robyn]

Open the hood and watch the AC belt while the engine is at idle.

The center span will likely be vibrating a lot.

This is the noise.