LBZ: Shudder/ Humming

[Pony Express]

Hey folks,
About a week ago I made a thread in the chassis/ suspension subforum about a few issues I had. Thanks to all who helped, fixed 2/3 problems. The last one still remains though, I have a pulsating humming noise when I drive at 60ish mph or greater. I am 99% sure it is something engine related because if I sit in park and bring the revs up to ~1000 ish I can feel the same "shudder" ever so slightly in my seat. I have no idea where to start- maybe cp3? Unfortunately don't have tools to check balance rates/ etc. at this time. Any ideas?

Thanks everybody.

Edit: Forgot to add, this has been going on for ~1 year now, I can't really feel it "surging" when I drive I only hear it.

 

[Pony Express]

Nothing? Somebody in the other thread mentioned cv axles but because I can "feel" it when I'm not moving I think its gotta be engine.

 

[AubleAK]

I'd find a scanner to look over everything

 

[chevyburnout1]

Possibly sheared crankshaft balancer pin since you said it does it revved up in Park. When my balancer spun the whole truck would feel like it was misfiring when taking off from a light.

 

[NC-smokinlmm]

Check your engine mounts...

 

[Pony Express]

Possibly sheared crankshaft balancer pin

Was the misfiring at takeoff the only symptom? My truck runs/ drives fine I can hear the humming (its sort of a pulsating humming) but I'm trying to catch it before I get stranded on the side of the road.

I looked at the motor mounts a bit ago they looked "alright" but I will be sure to doublecheck them. Is it big pain in the ass to replace them? I read that some people don't even hook their engine up to a hoist...seems kinda risky.

 

[chevyburnout1]

Yeah basically just a rough vibration from a dead stop, and a little more smoke than usual on the stock tune. Humming sounds like it would be a higher vibration than that though. Possibly something rubbing against the firewall.

 

[NC-smokinlmm]

I have changed them without a hoist, its no big deal. You can check them by standing on the brakes and reving the truck up in gear and see how much your engine is moving in the engine bay. The last one I helped with had the engine compartment insulation under the hood all torn up bc the intake tubing was rubbing it when the engine moved excessively under load...