241C Transfer Case Vibration WEIRD???

[Midnight]

1992 GMC K1500. 700r4. 6in Suspension Lift. I'm getting a vibration in my transfer case ONLY with the A/C switched on and even if I have the transfer case in neutral. Everything else seems to be working just fine. Mechanic thinks its probably the dreaded "pump rub". I guess my question at the moment is - Would I get the rub even with the case in neutral? Hopefully you all will have some comments/suggestions on anything else that might make sense to me. Thanks!

 

[Midnight]

1992 GMC K1500. 700r4. 6in Suspension Lift. I'm getting a vibration in my transfer case ONLY with the A/C switched on and even if I have the transfer case in neutral. Everything else seems to be working just fine. Mechanic thinks its probably the dreaded "pump rub". I guess my question at the moment is - Would I get the rub even with the case in neutral? Hopefully you all will have some comments/suggestions on anything else that might make sense to me. Thanks!

Wanted to add some pics for reference...

 

[Cadillacmak]

I have had front driveline rusty u-joints mimic a transfer case vibe while in 2x4. I think I would try in neutral and 4x4 to see if it goes away or changes just in case.

 

[Midnight]

I have had front driveline rusty u-joints mimic a transfer case vibe while in 2x4. I think I would try in neutral and 4x4 to see if it goes away or changes just in case.

That's what I was saying... doesn't go away in neutral, 2x4 or 4x4.

 

[Schurkey]

I have no idea how using the A/C can cause problems in the transfer case, unless it's nothing more than engine RPM related, not A/C per se.

When you say it happens "in neutral", do you mean when stopped--vehicle speed ZERO?

 

[Midnight]

I have no idea how using the A/C can cause problems in the transfer case, unless it's nothing more than engine RPM related, not A/C per se.

When you say it happens "in neutral", do you mean when stopped--vehicle speed ZERO?

"in neutral" as in the transfer case is in neutral.

 

[Schurkey]

When you say it happens "in neutral", do you mean when stopped--vehicle speed ZERO?

"in neutral" as in the transfer case is in neutral.

Fine. Is the vehicle STOPPED? Or MOVING, coasting in neutral?

 

[Midnight]

Fine. Is the vehicle STOPPED? Or MOVING, coasting in neutral?

It's with the vehicle stopped. The noise seems to go away when it's moving.

 

[Schurkey]

"Pump rub" is new to me. Never heard of it before. I can't comment on "pump rub" beyond that.

The entire output side of the gear train would be stationary, the driveshafts/U-joints would be stationary, the differentials would be stationary. I suppose the input side of the transfer case could be rotating. So a problem on the input side--failing bearing or thrust washer, for example--might be noisy.

I think you're mis-diagnosing a vibration from something else--an exhaust heat shield, the flexplate, the serpentine belt/tensioner...and getting caught-up in "transfer case" when the problem is somewhere else.

But I've been wrong before, and I'm not there to inspect it.

 

[Keeper]

with A/C on? maybe that load causes a more pronounced engine vibration that is transferring, like Schurkey was saying. How do the engine and tranny mounts look?