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1995 Jeep Grand Cherokee Limited, 4.0L, NP249, Dana 30, Dana 35
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6 Posts
Discussion Starter · #1 ·
There's a loud buzzing sound (propeller airplane-like?) only during acceleration that begins at 50mph and gets louder until I hit 70mph, at which point it abruptly silences. If I'm going 60 to 65mph and accelerate a bit (not causing a downshift), the sound is rhythmic, like a HUMM, HUMM, HUMM.

While accelerating from 5 to 20 mph (after vehicle is warmed up) there's a rough/bad bearing rotational like noise that I can only hear inside the cabin, if I stick my head out the window I can't hear it. I do hear some slight chirping, so I checked my rear driveshaft, it has no play, front driveshaft BARELY wiggles at the double-cardan that goes into the transfer case. The centering yoke seal (dust protection seal?) in that double cardan appears dry/brittle.

My radiator fan is not rubbing on anything. I replaced my front wheel bearings/hubs the other day, and a couple weeks ago replaced the engine and transmission mounts. I drained and refilled the front and rear diffs, front fluid was BLACK, rear fluid was very dark. My transfer case is full but could use a fluid change, I checked the fluid for metal and it was normal for needing a change. The noise started before all of these repairs, and none of them made an improvement.

Any help/sense of direction at this point would be greatly appreciated.

This is the sound at highway speeds. Starts coming on at the 20 second mark. Skip to 50 seconds to hear the HUMM, HUMM, HUMM.

This is the sound at slow speeds. Gravely/rotational/bearing noise is at the beginning, chirping is at 58 seconds. Sorry about the wind.
 

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Registered
1995 Jeep Grand Cherokee Limited, 4.0L, NP249, Dana 30, Dana 35
Joined
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6 Posts
Discussion Starter · #3 ·
If you haven't viewed this:
I sure had! Great video, awesome channel. I was thinking that might be it, even though movement was so miniscule. When you posted, I had already had u joints and a centering yoke on the way from Denny's Driveshafts and decided to wait until I replaced them to reply. The noise is now gone. Thanks for your reply.
 

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Registered
1995 Jeep Grand Cherokee Limited, 4.0L, NP249, Dana 30, Dana 35
Joined
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6 Posts
Discussion Starter · #4 ·
I almost forgot. Just for the sake of putting the information out there. I have the front driveshaft with the CV boot going to the front diff. I bought two non-greaseable Spicer 5-1310X u joints (used copper snap rings when installing), non-greaseable Spicer 211544X centering yoke, and Spicer 2-86-418 rubber boot. I ordered from Denny's Driveshafts. My order was over $99 so it qualified for free shipping and the parts arrived within 3 days.
 
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