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Very Distinctive Roar on Deceleration and Left Turns

XJoholic

NAXJA Forum User
Location
Arkansas
2001 XJ 4x4, 151k miles, 100% stock. I have a very distinctive loud roar. I think have enough info for someone here to help diagnose:

Roar is present when:
- Decelerating in a straight line or corning left (loudest at 40-mph or under)
- Left turns in curves (at speeds 10-mph or above)
- Pretty much anytime I take my foot off the accelerator

Roar is NOT present at all when:
- Accelerating (at any speed)
- Right hand curves (completely goes way when I bank right, at all speeds)
- In neutral. If I slip tranny into neutral while the roar is present, it completely goes away, at all speeds and all conditions.

Hopefully that is enough for someone to help. The roar is loud, it takes over the cabin and I can't even hardly hear the radio. But pop in neutral and it all goes away. Put the foot into the gas, and it all goes away.

Iv'e wiggled the drive shaft at both ends and do not feel any play. I checked my rear diff fluid, and it was full. To me the sound seems to be coming from the rear, but I know it can be deceiving. I also pulled rear brake drums, and shoes are fine, nothing broken. Tomorrow I plan to check the transfer case fluid.

Thanks for any help guys!
 
..... If I slip tranny into neutral while the roar is present, it completely goes away, at all speeds and all conditions.

This makes me suspect something related to engine torque. Check the motor mount to engine block bolts. Suspect worn out or damaged motor mounts, and/or the transmission mount. Carefully inspect the exhaust looking for signs of contact with the unibody and especially with the transmission cross member. Confirm all the exhaust mounts are present and in functional condition.
 
Check your front Unit bearings.

Jack up the front and grab the tire at 12 and 6 o'clock and push/pull. If it flops around you found your bad unit bearing.
 
This makes me suspect something related to engine torque. Check the motor mount to engine block bolts. Suspect worn out or damaged motor mounts, and/or the transmission mount. Carefully inspect the exhaust looking for signs of contact with the unibody and especially with the transmission cross member. Confirm all the exhaust mounts are present and in functional condition.

Thank you, I’ll look at all that tomorrow and post back.
 
Check your front Unit bearings.

Jack up the front and grab the tire at 12 and 6 o'clock and push/pull. If it flops around you found your bad unit bearing.

Thanks. I’ll do that tomorrow. I did check my front wheel bearings. They seem as tight as dicks hat band
 
Nope! Just be careful as it will drive a little different.
 
Just for those that aren't aware, this "remove the rear drive shaft and go for a drive" trick only works on the 97-01 models, and the portion of the 96s that got the same tcase as a 97+.

On 84-95 and some early 96 models the rear tcase output isn't sealed without the shaft in place, unless you have a slip-yoke eliminator (a.k.a. fixed yoke) conversion installed...
 
Just for those that aren't aware, this "remove the rear drive shaft and go for a drive" trick only works on the 97-01 models, and the portion of the 96s that got the same tcase as a 97+.

On 84-95 and some early 96 models the rear tcase output isn't sealed without the shaft in place, unless you have a slip-yoke eliminator (a.k.a. fixed yoke) conversion installed...

Thanks for the clarification.. you may have saved a few folks!

I took my drive shaft off today and ran it down the road in 4x4 mode. The noise was 100% gone! So it was for sure the rear-end. I had lateral play (in and out) of the pinion yoke. I took a big a$$ break bar and tightened the pinion bolt, it went almost a half turn. After that the in/out play was gone. I reinstalled the DS and went for a test run. The roar sound was a little better (still there) but now I have a slight roar at acceleration. Not sure what else to do. Carrier bearings? Gear? Find me another axle? Actually I may sell the Jeep as-is. I have another XJ that I’m building up and really don’t need two of them anyway.
 
Grab another rear axle from a junkyard. U-pull-it rear ends are about $100. Just be careful to grab the correct ratio.

Or check out Car-Part .com
 
Grab another rear axle from a junkyard. U-pull-it rear ends are about $100. Just be careful to grab the correct ratio.

Or check out Car-Part .com

Thanks. I checked a couple local junk yards who have their inventory online. Found a couple axles, providing gear ratio's match, however both I found have high miles, over 200k. Wonder if I'm getting back into the same situation with installing high mileage axle?
But then I guess anything is better than what I have now. I've helped my brother swap axles on his jeep more than once over the years, and I have good tools, so this is prob the route I will take (if I don't sell it as-is first).
 
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