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xjcowboy01 04-09-2013 11:43 AM

Whining at 40 mph
 
Hey guys,
I've managed to get a ton of vibrations and noises sorted out with my jeep but theres just one last gremlin I haven't been able to figure out. A noise occurs starting at aroun 30 mph and grows louders until about 40 mph where it just about drives me nuts. After that the whine/howl cuts down a lot. The sound is just like the road noise produced by a tractor trailers tires.

There is very little vibration from this sound, it can only be felt as a sort of groan throught the steering wheel. The noise is completely independant of front driveshaft and of engine rpm's or load, meaning it doesn't matter if the front shaft is in or not and it does not change (at least not very much) from acceleration, deceleration, rpm, or what gear its in.

I did not notice this noise until a few months ago but 2 years prior I had replaced both the front hub bearings with Timken bearings and replaced both of the rear wheel bearings as well with Napa parts. Tires are DynoPro AT's and seem to be in pretty good shape but are slightly feathered with about 10k miles on them. Rotating them did not make a perceiveable difference.

One last little note, I had a Tom Woods driveshaft in for at least 5k miles that did not mate perfectly to the transfer case output yoke and thus caused the driveshaft to act out of round and out of balance. That problem is solved but could have let to others.

Jeep Info: 2001 XJ 4.0L NP231 Chrysler 8.25, 3.55 gears, 31" all terrains, Dana 30 LP, Pro Comp HD SYE.

What do you guys think could be causing this constant whine/howl at 40?
Please help, and thank you for taking the time to read this.

habbyguy 04-09-2013 12:34 PM

You'll need to give us some more input to get any kind of good guesses. Does it change at all during acceleration or deceleration? How about going around curves at speed?

FWIW, my Chrysler 8.25 rear diff howled like a lovesick wolf by the time I finally broke down and overhauled it. Then again, so did the hard-as-a-rock tires that were on it when I bought it.

redding1327 04-09-2013 12:38 PM

I'm just guessing that if you let off the accelerator when it is howling it nearly stops instantly. If so, I would think carrier bearings. Mine is doing the exact same thing. It happened just a few weeks ago after I had to tear my rear end down. I think I set the carrier wrong.

xjcowboy01 04-09-2013 12:48 PM

Habbyguy: As stated in my post the noise does not change with respect to anything but speed. Accel, decel, turning, hard braking, rpm's gear, nothing changes it but speed.

Redding1327: No it does not go away when I jet off the gas.

habbyguy 04-09-2013 02:09 PM

My money's on either tires or those Napa bearings on the rear axle. The best diagnosis would be to borrow a set of wheels from someone else to see if the problem goes away with different rubber.

xjcowboy01 04-09-2013 02:50 PM

I agree with you 100% sir, but I haven't been able to find someone with a set of good tires that I couldswap with. I am wondering about those bearings as well. It's a shame I replaced them because I was chasing a vibration problem and the factory ones were'nt even bad. Any suggestions for the best set of rear wheel bearings?

habbyguy 04-09-2013 03:13 PM

You can't go wrong with Timken bearings. You know what you're getting that way. There are some manufacturers who build spec parts that might not have a perfect fit, or could have quality or material issues. I'm cheap, but will normally try to buy the good stuff for those applications where a failure could cause real problems or be a huge hassle to repair.

It occurs to me that you would get different sound from the tires (if that's the source of the problem) on different road surfaces, particularly on the wet (or better, snow, though you do have to be careful testing it at over 40mph then!). ;-) If you still hear the same noise when you're on a soft dirt road or gravel, you can pretty much rule out the tires.

Jeepy84 04-09-2013 06:10 PM

Even different pavement surfaces would change the pitch of the sound.

What about u-joints? You said you have been busy chasing down vibrations, maybe you didn't get one fixed soon enough and maybe you burned up some needle bearings?

xjcowboy01 04-09-2013 09:56 PM

The pitch does not chanfe with respect to road surface at all, its always they same. As far as u joints I have had 3 different driveshafts in ther while chasing down those other vibrations , all of them with new ujoints and 2 of them were completely rebuilt twice during this and the whine did not change. I was thinking either tires or wheel bearings but since the wheel bearings were fairly new I wasn't sure whether to look into getting an axle rebuilt if the carrier bearings were bad.

Since the sound dos not change at all is it safe to say that it is in the front axle? I need to pull the diff cover and look at the front but I have done the rear diff recently and it looked perfect.

**Almost forgot to add that the sound seems to pulsate ever so slightly at about the same rpm's as the tire/wheel bearing rpm.

Does the fact that this happens from 30-40 mph point toward anything in particular?

habbyguy 04-10-2013 07:20 AM

The fact the noise is constant on different road surfaces pretty much rules out the tires (good news / bad news).

It's hard to imagine that such new wheel bearings would go bad, but that's always a possibility. At the very least I'd jack up the front end and see if you can feel anything but silky smoothness from those new(ish) wheel bearings.

It may be pointless, but have you tried driving with the rear driveshaft out? At least it's a relatively easy test that might tell you something.

Barring anything definitive showing up otherwise, I suppose the carrier bearings are very likely suspects. I don't know of any easy way to test them though.

pipedreamphoto 05-07-2013 10:08 PM

I have, what sounds like, the exact same issue but with a bit of vibration as well. I noticed when I checked my front drive shaft for joint play that there was actually play in the shaft but that it seem to be in the diff not the joint. I have lots of other issues that need to be dealt with before I tackle the front diff. Both front U-joints being the next major job I need to tackle. Is there play in your front shaft where it meets the diff? I have a 97, mostly stock. Should be pretty close to the same vehicle as yours.

xjdantheman 05-09-2013 04:08 PM

i think in an other thread of a similar noise the issue turned out to be the roof rack was too far forward causing a whistle sound.

xjcowboy01 05-11-2013 08:55 AM

Wells guys sorry its taken me a while to get back, I've been too busy with work. So this whining has gotten much worse lately but I'm almost certain its the tires I just haven't found a good set of tires to try swapping with to see for sure. Heres how I came to that conclusion:

The other day on the way home from work as I was drivng down the freeway the sund got much worse just before my rear passenger side tire sidewall blew out. So I put n the spare and drovedown to discount for a new one and in less than a mile I could tell the difference in the noise with the spare on. It seemed to be much better. So discount gives me a new tire but notices I have one fairly new tire on the fron passenger side (wich they had replaced because I had a tire with severe cupping). They swapped the newish tire from the front to the rear drivers side (yeah criss-cross I know).

After leaving there the sound has been much worse since and gets bad if I hit the breaks at about 40mph. So it appears when the front tires have more load on them when breaking the sound ghets worse. I took a look at the drivers front tire and it appears to be delaminating just like the other did. Discount refuses to replace the tire because "it's not bad enough to be a safety concern". What a bunch of BS. When I get a set of different tires on there I'll know for sure.

So now after a little research I'm starting to believe the problem is from cupped tires especially since the sound showed up right after a rotation and balance. My question is what could be causing the cupped tires? My shocks are bilstein 5125s and they are in good shape I believe. All other suspension components appear to be in good shape as well. I just don't want this to happena again if I get new tires. Any tire gurus out there that can help?


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