Swapping axle shafts...will this solve the problem?

So I have a 29 spline 8.25" with 4.10s and an Auburn. At 30-50 mph the rear end starts to make a very loud noise. Under or over those speeds however, there is no noise.

The guy who did the gears has rechecked them twice, and rebuilt the diff once, just to make sure. He says that he thinks it could be an outer bearing of some sort, or an axle shaft.

I just picked up a spare set of shafts, and was thinking of putting those in, and repalcing all the bearings and seals that he did not replace.

So my question to you: Could the shafts or a bearing be the culprit, or should I check something else?

Thanks for the help, and lemme know if you have any other ideas.

Fergie

Fergie said:

So I have a 29 spline 8.25" with 4.10s and an Auburn. At 30-50 mph the rear end starts to make a very loud noise. Under or over those speeds however, there is no noise.

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From what I know the 8.25 is a PITA to setup and it's noisy. Both myself and 2 other guys had same guy do our 8.25 and 2 were quiet (mine included) while one was noisy. IIRC the guy with the noisy one had it redone by someone else and it's nice and quiet now.

Also can you describe the noise? is it a howl? whistle? banging? clunking? Also did you see the pattern? Maybe you should run the pattern yourself to see if he set it up right (I saw the pattern pics from the Yukon install book and even though I'm no expert, not all of them looked to be good even though they were supposed to be: my suspicions were later confirmed by someone who sets the axle up).

Fergie,

unsure of what is causing your noise, but if you end up replacing your shafts let me know if you'd like to sell one of them as a trail spare. I'd be interested.

Have you eliminated the possibility that it's driveline related? Loud sound is not much for us to go on. I'd remove the rear driveline and run it in front wheel drive to see if the sound is still there or if it changes at all. If you don't have an SYE, you'll need a plastic plug for the t-case output to do this.

It is a howling noise that occurs at the speeds I mentioned. I may take the Jeep to a local shop and have them check it out, if the cost isnt too much. I dont mind changing the shafts, and I dont think that checking the pattern would be too bad, but I gotta do some reading to see how involved this will be.

EricsXJ- If I change out the axleshafts, I will sell you one for half the price I bought the pair for, which would be less than $40 including shipping.

Fergie

Goatman said:

Have you eliminated the possibility that it's driveline related? Loud sound is not much for us to go on. I'd remove the rear driveline and run it in front wheel drive to see if the sound is still there or if it changes at all. If you don't have an SYE, you'll need a plastic plug for the t-case output to do this.

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Pretty much eliminated that possibility. The noise was there directly after the axle was swapped out, and the previous owner mentioned the noise to me, but he seemed to think nothing of it, however I would like it solved.

Fergie

Fergie said:

Pretty much eliminated that possibility. The noise was there directly after the axle was swapped out, and the previous owner mentioned the noise to me, but he seemed to think nothing of it, however I would like it solved.

Fergie

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What do you mean "axle swapped out"? I know I'm not hearing the noise, so this is difficult, but I can't see a reason that an axle shaft would cause a noise to come in at 30 and go away at 50. It seems that it would be more vibration/harmonic related. It could be an axle bearing I guess, but they normally will just get louder with speed, not go away after a certain speed.

You said "pretty much eliminated that possibility" referring to driveline.......how?

Goatman said:

What do you mean "axle swapped out"? I know I'm not hearing the noise, so this is difficult, but I can't see a reason that an axle shaft would cause a noise to come in at 30 and go away at 50. It seems that it would be more vibration/harmonic related. It could be an axle bearing I guess, but they normally will just get louder with speed, not go away after a certain speed.

You said "pretty much eliminated that possibility" referring to driveline.......how?

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I swapped out the stock axle, another 8.25", for the one I have now. Could a bent housing be the cause of the noise? It is more of a humming that grows and then disappears, so yeah, it could be harmonic/vibration related.

I know it is not the driveline because the previous owner of the axle told me he had the same noise when he had the axle. The mechanic that did the gears is a guy we both know, and the two of them rebuilt the diff after the first time the gears were set. The mechanic said the noise could be a bearing or sahft, but wasn't sure.

I just have no idea what is causing the noise, and what would cure it. Please helP!!

Fergie

Fergie said:

I just have no idea what is causing the noise, and what would cure it. Please helP!!

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I'm almost willing to bet $$ on a bad gear setup. Talk to SafaryAry as I think he had some whine in his 8.25 from a set of gears a while back.

Just thinking here, since we have so little to go on, so bear with me.......you asked for help. A sort of humming noise that could be a vibration/harmonic would likely be coming from a part that is turning fast enough at 30-50 mph to make that noise. This points to something turning at pinion/driveline speed rather than wheel/axleshaft speed. Part of diagnosing a problem is ruling out possibilities. I'd still recommend removing the driveline, just to see if anything changes, and to positively rule that out. Maybe the pinion flange/yoke is bent, causing a noise from the pinion u-joint. Maybe the pinion bearing is bad, maybe the gears themselves are defective. Maybe you lost a needle bearing out of the pinion u-joint without noticing it while installing the new rear end.........check out the easy stuff to eliminate it, and don't assume anything. One of the hardest situations to diagnose is when a part is worked on, but another part randomly goes bad at the same time, or both were bad.......it happens.

FYI, I do this for a living. I run a shop, so I get to help the mechanics find the hard stuff. Last week we had a truck with a very slight vibration, the mechanic pulled the driveline and sent it to the driveline shop to get checked out. The driveline shop said the shaft was bent, so they straightened and balanced it. The driveline was installed and nothing changed, the vibration was still there. He got me and we went for a ride, I told him I bet it was a bad double carden joint, even though the driveline shop had just checked it out. Sure enough, that was it, and the driveline shop did the repair at no additional labor cost.

Check everything out, until you know for sure. Have fun,

Kejtar said:

I'm almost willing to bet $$ on a bad gear setup. Talk to SafaryAry as I think he had some whine in his 8.25 from a set of gears a while back.

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Ah, the 8.25 ghosts are back again. I told SafariAry not to build his 8.25, and he did it anyway including parts from my 8.25. That axle is long gone, and I think that now he listens to me .

I rebuilt my 8.25 entirely, including all bearings and alloy shafts, after my initial setup got noisy just like yours (howling noise at 35-50 mph, only on deceleration). Even used a different brand of R&P the second time, and the wear pattern on the first was good upon removal and inspection. It finally got loud enough that I ditched the 8.25.

What is interesting is that mine also had an Auburn, and you have to do some case grinding to get those things in. I wonder if there is something about that setup with lower gears that just makes noise. In any case, I wasted a lot of money trying to get it to go away, and I tend to advise people to be careful building the 8.25 as it can have a tendency to being noisy. For some, this ruins what is otherwise a decent axle. Most people seem to have no problems.

I have very little to offer you other than pessimism. If you have to use a shop to try to cure this problem, your purchase may be getting a lot more expensive to the point you could have bought much better axle. I think that, by the time it was all done, I spent $2,700 on my 8.25 including the final diff rebuild.

Complete
Waste
Of
Money.

Nay

Goatman- What doesnt sit right with me is that the axle made the noise when the previous owner, AND me, so I dont think it would be the driveline.

Anyway, I will try all of these things you have suggested, so I dont have to spend a lot of money. If it turns out to be more, I may just start looking for a D44 with 4.10s and a non factory LSD.

Keep the thoughts and suggestions coming please!

Fergie

quick thought for my edification:

If it were the gears making noise, then wouldnt they make the noise all the time?

Fergie

Ive found my 8.25 to be extremely sensitive to anything and everything! You didnt say what type of driveshaft/sye your using? I had "that" noise after 2 different gear set-ups,most of it was shimming(there was a very narrow range is likes),tried 2.5*,3*,and 4* shims to dial it in.Also needed the driveshaft to be constantly lubed and in PERFECT balance to decrease the hum.I dont even notice it any more!!!!!!!!!!!Forgot to mention the change from a H&T kit to a HD sye kit,it all played a part!

Fergie said:

EricsXJ- If I change out the axleshafts, I will sell you one for half the price I bought the pair for, which would be less than $40 including shipping.

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Thanks!

BTW, I don't know if you read in the other 8.25 thread we had recently but I also have a humming, droning sound but only starts at about 65 mph and ONLY when I am on the gas. Yours may be a bit different but is it possible that both you and the other guy had problems with both your drivelines? Someone in the other thread suggested to me that my problem was a driveshaft vibration as I only notice it now after the 4.56's were installed due to the increase in RPMs. Well... I think they are right and after another measurement I got my actual angles correct. (The mechanic said pinion angle was very good at it looked good eyeballing it...) but... in actuality the angle was at 7* which isn't ideal for a SYE and CV shaft (but I had no vibes before...) so I swapped out my 2* shims for 6* shims which brought my angle to 3*. I did a test drive and unfortunately the droning is still there but seems to be a slight bit improved.

The next thing I will do is get the driveshaft balanced (a 2nd time...) and I also need to shorten it by 1" so might as well do it. Worse case scenario, I can live with my noise since it is pretty minor (and hey maybe if I increase tire size to 35's like I'm planning in the future, it will slow the driveshaft RPMs down to the range I won't hear the noise)

So just curious what your angles are?

Jumpin Jesus on a pogo stick!!

It completely blew my mind that the noise goes away when I let off the gas!

I'll check my angles tomorrow or the next and get back to you guys on it. I am running a 3* shim and no SYE with a 231 and this is a 95' XJ.

Fergie