Droning noise - thinking it's driveline related

Well, finally got this thing on the road after 5mo of sitting. New 3" lift, 31" tires, brakes, all new fluids, tune-up, etc. Real project so far, but I like it. Only put 25 miles on it since all of this and today, on mile 17, at about 40mph I start hearing a droning sound. I only hear it when on throttle, but with a load. I verified this by shifting into neutral and revving and no noise. Also no noise when coasting. At first I thought it was from under me - trans or TC, but it started to sound more like the rear. Don't notice it much slower than that and it's not real loud, but definitely audible. I didn't get over 45, so I have no idea if it gets louder, shakes, etc. What should I be looking into?

Rear driveshaft u-joint could be the main culprit.

Try throwing some washers into your crossmember, to drop the t-case a little, and see if that helps. If it does, I'd look into either an aftermarket t-case drop, a better home-brew one, or a SYE kit.

I was originally planning on a TC drop, but was also planning on 4.5". Since I stayed w/ only 3", I decided not to b/c it seems that most early XJs (mine is a '91) don't usually require them. I'll pick one up though - at least they're cheap!!

Sorry don't mean to hijack

Funny, I get thoese symptoms too.

But, I am STOCK.

You suggest I install a TC drop???

moparmatt said:

Sorry don't mean to hijack

Funny, I get thoese symptoms too.

But, I am STOCK.

You suggest I install a TC drop???

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Um, I'm not an expect, but it shouldn't be an issue to solve a stock suspension - your driveline angle is fine. I'd guess that you have something on it's way out - u-joint somewhere.

I have the same problem... Chrysler 8.25 rear end. I hear it at about 30mph on the road while on the gas. Not as much when coasting.

I lifted up the rear and put it in gear at about 30mph I heard a howling/light metal scraping noise from the pumpkin. It just started about a week ago. I installed new u-joints about 6 months ago for maintence reasons. I would love to know what this is before I tear it apart or get another assembly

kjpeter said:

I have the same problem... Chrysler 8.25 rear end. I hear it at about 30mph on the road while on the gas. Not as much when coasting.

I lifted up the rear and put it in gear at about 30mph I heard a howling/light metal scraping noise from the pumpkin. It just started about a week ago. I installed new u-joints about 6 months ago for maintence reasons. I would love to know what this is before I tear it apart or get another assembly

Click to expand...

Well, I've had a rear go out before and I guess it was just a louder version of this sound. I just can't see why out of the blue this happened. I'm pulling my diff. soon - by this weekend at least to inspect.

I remember seeing pictures of a guy that did what you said - vehicle lifted and in gear - needless to say it came off it's jackstands or whatever he was using and flew through the garage door. I think he had it up to 60 or something though!!

just found this on a website....

"I had a similar-ish problem. i'd get a humming sound on accleration, and nothing on decel. I took apart the rear axle. Nothing looked bad. All the bearings looked fine. No pitting, etching, nothing. I pulled out the rear drive shaft and found that the bearing that the yoke of the rear drive shaft rides on was all scored up... By the time that happened, the t-case was junk anyways. I drained the fluid and it came out looking like strawberry milk...."

Might be the problem since we are running different differential assemblies

Hmmm. I recently changed my tc fluid and it looked like used oil - that was about 40 miles ago and then 30 miles ago I went muddin' and got pretty deep. Haven't changed the fluid after that incident, but it was on my list of ASAP items - just had to get this lift & brakes done first. Guess I'll find out this weekend when I hank the rear diff too.

TC did cross my mind though - along w/ tranny b/c when I first heard it I thought it was coming from under me. I'll check fluids and drop TC an inch and see what happens from there - hopefully just a u-joint.

Ok I'll try to help by adding my recent experience...hopfully it'll save you guys a little leg work during the trouble shooting process.I have the same exact drone starting around 35mph.....

I originally thought ds ujoints but they are new(ruled that out by removing rear ds,see below),cant be t-case its brand new from jb conversions with sye.I suspected rear axle so I removed rear driveshaft and drove on the front shaft up to the speed that the noise would normally start and the noise is gone.What I've narrowed my noise down to is either a rear pinion bearing or shot ring and pinion.I was also thinking rear axle shaft bearings but thats not it because with the rear shaft removed the axle shafts are still spinning so if it were those bearings they would be making the noise,although this may or may not be your case.The only way to find out is to remove the rear shaft and test drive it to see if the noise goes away.
**caution**If you don't have a sye make sure you seal the rear output on your t-case so you don't loose t-case fluid!!!

HTH.atriot:

I removed the rear DS... brought it up to 35 and noise is gone. Brought DS to a driveline shop and had them install new u-joints and balance the shaft (I accidentaly dented the old one). havnt been able to test drive it but Im sure its still going to be there. if it is i get to replace bearings.