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Front drive shaft noise

Tyurbs

NAXJA Forum User
Location
Colorado
So I was having some noise from the front of this new to me 1992 xj. After some investigating I found that the front left axle shaft U joint was basically non existent. While investigating I didn't think the front drive shaft U joints seemed bad at all but after fixing the axle shaft joint I still had an odd noise similar to slight grinding noise coming from the front end. I figured I'll just remove the front drive shaft and if the noise goes away then that's the problem. Well, the noise went away but now where does that leave me. What could be making noise in the driveshaft besides the seemingly good u joints? Do I just start replacing the u joints in the driveshaft?
 
You've also got the centering ball and the splines to grease and worry about wear!
 
You've also got D30 pinion and diff bearings that could be making noise. That noise gets harder to hear if you remove the front driveshaft. In my area, I can have the drive shaft rebuilt by a shop for about 80$. They'll replace the centering ball and joints and grease everything up good. I'd say that is money well spent if you can find someone to do it for you for the same cost. I know guys on here have done the rebuild themselves, and maybe that is something you want to attempt.

I'd recommend a change of front diff oil and inspect the front diff carefully as well.

my .02$
 
Will definitely be inspecting the front diff soon. I've never had a Jeep nor 4wd so I just have to dig in and learn exactly what's happening in there. With the ds removed it's quiet. It's hard for me to imagine that the driveshaft would amplify front diff noise in that manner but definitely a possibility I will be looking into. Regardless the front ds is being rebuilt either by me or a shop. I've yet to decide n that it really just depends on what kind of pricing I can find. But shoot 80 doll hairs sounds doable
 
Just completed a visual inspection of the front diff. I opened it,drained it, cleaned it then spun the wheels in hopes of hearing any noise. Nothing out of the ordinary except the fluid was grayish black. Waiting on the Permatex to dry now. Maybe changing the fluid will do the trick. I didn't hear any odd noises like a bad bearing or anything.
 
Unfortunately, you wont be able to hear a bearing noise spinning by hand. You really need to have things spinning at road speeds. Changing the gear lube is a really good start, though.

Locate four jack stands and a mechanic's stethoscope. Get the tires off the ground and have a friend run the truck up to the same speed you hear the noise (in 4wd). start listening to different parts until you hear the noise. Just don't get tangled up into spinning parts.
 
Well as suggested earlier in the conversation I now believe the noise is coming from the front diff and being amplified by the driveshaft. I had the Jeep on jack stands in 4wd with a stethoscope as suggested and the noise is most certainly coming from the diff. It's sounds a lot like a bad bearing/s. I recently was just inspecting in there and the gears looked fine. No metal in the fluid. I did see two bearings in there where the axles come in. How hard is it to replace these ?
 
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