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whining noise...

Robs92XJ

NAXJA Forum User
Location
Georgia
I've been noticing a whining-type noise lately. I'll try to describe it the best I can.

'92, 4.0L AW4

It sounds a lot like gear whine, in my opinion; like when an old front-wheel drive car backs out of a driveway in reverse. It's purely RPM dependant, and you can hear it all the way from idle to at least 4k rpm (the highest I've revved it recently), getting a little louder and higher pitched as revs increase. It's not *incredibly* loud- I have to turn off the HVAC and radio completely to really hear it. You can hear it better from outside.

The interesting thing about it is that it goes away instantly and completely when the tranny's in overdrive. This made me think it was the transmission/torque converter. I checked the fluid level today and it was fine- I replaced the fluid a couple times in the past few months with Dex III. I can't really remember when this sound first appeared to try to correlate it with anything that I did maintenance-wise.

While under the hood to check the fluid, I tried to pinpoint the sound and it really did NOT sound like it was from the transmission; it actually sounded like it was from the front of the engine, around the AC compressor area.
Turning AC on and off made no difference except to change the rpms a little. I suppose it could be a pulley, but I checked them a few months back when I changed the serp belt and they seemed fine then, and more importantly it doesn't make any sense that a pulley would just stop making noise all of a sudden when you shift into OD, or does it?

That's about all I've been able to find out. Was wondering if any of you fellas had any ideas or similar experiences. Thanks for any help I get- Rob
 
My 91 Sport just started this four days ago - right after I changed the oil. Having just moved from GA to OH, I attributed it to the extreme cold, and that I put in too heavy of an oil (10W30). Going to change it to 5W30 this weekend.

Does yours do it all the time, or just when it's cold? You described my noise to a "T", only mine goes away after the engine has warmed up and the oil-pressure has dropped (from finally heating the oil, I guess).

Could it be the oil pump?
 
If the noise truely goes away when in OD (or is it when the torque converter locks up) and is completely RPM dependant then I would suspect a torque converter problem. If it didn't go away in OD I might suspect a pulley bearing. Maybe the noise is still there but you can't hear it when the RPM's drop because of wind noise.
 
I have this sound and I've been wondering if it could be low fluid in the transfer case. My sound completely goes away at 1:1 ratio(4th gear) but I have it in all other gears, and 2hi, 4hi, 4lo

Also I have a 5 speed
 
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