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  #1  
Old October 27th, 2005, 17:37
witstick witstick is offline
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howl from rear

Hello, my 98 classic has a rather loud howl comming from the rear when goING about 40-50 mph . Sound changes when i get onor off gas. I dont hear it at other speeds. What could it be? bad rear end?
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  #2  
Old October 27th, 2005, 18:06
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Kejtar Kejtar is offline
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Re: howl from rear

Quote:
Originally Posted by witstick
Hello, my 98 classic has a rather loud howl comming from the rear when goING about 40-50 mph . Sound changes when i get onor off gas. I dont hear it at other speeds. What could it be? bad rear end?
bad pinion bearing? hungry kids?
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  #3  
Old October 27th, 2005, 18:07
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Fergie Fergie is offline
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Re: howl from rear

8.25" rear?

Live with it, or switch axles.

Fergie
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  #4  
Old October 27th, 2005, 18:18
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Kejtar Kejtar is offline
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Re: howl from rear

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Originally Posted by Fergie
8.25" rear?

Live with it, or switch axles.

Fergie
my 8.25 never howled.... In either jeep.
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  #5  
Old October 27th, 2005, 18:20
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Re: howl from rear

Quote:
Originally Posted by Kejtar
my 8.25 never howled.... In either jeep.
Soooo...what does YOUR Jeep have to do with HIS axle??


Oh yeah, nothing at all.
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  #6  
Old October 27th, 2005, 18:22
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Kejtar Kejtar is offline
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Re: howl from rear

Quote:
Originally Posted by Fergie
Soooo...what does YOUR Jeep have to do with HIS axle??


Oh yeah, nothing at all.
Nothing except it means that he doesn't have to live with it: if there is something that is howling he can address it and things should be quiet again.
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  #7  
Old October 27th, 2005, 21:34
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BeJay1981 BeJay1981 is offline
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Re: howl from rear

I would lean towards a bearing going bad. Although having a silent axle is a rare thing. My 01 with a 8.25 has a very faint whine.

Did you recently tow something heavy or take a long trip? If it is a bearing have it checked out fast cause if there is now playin the bearing it could wear the ring and pinion funny causing a premanent whine, and that is no fun.
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  #8  
Old October 28th, 2005, 06:19
BrianB BrianB is offline
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Re: howl from rear

'93 8.25 I am pretty sure. It howled from day one and I took it in under warranty to have it checked out and of course the dealer said it was normal.

My whine comes in when kind of steady on the pedal at roughly 55 mph. I don't believe it's gotten worse over the years, but the axle swap is on my list of things to do when gas goes back down to $1.89 a gallon.

Brian
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  #9  
Old October 28th, 2005, 07:45
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rumblebelly rumblebelly is offline
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Re: howl from rear

Sure it's not the exhaust? I get a weird resonant howl from where the tailpipe bends up over the axle on my 00 Classic at roughly 1700, 2500, and 3000 rpms.

I've learned to live with it, even though it can easily be heard over a moderately loud radio.
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  #10  
Old October 28th, 2005, 08:16
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Re: howl from rear

The trick is to figure out if it's the axle bearings, the pinion bearings, the carrier bearings or something else.
Axle bearings often change pitch in a turn and most always start seeping gear lube onto the brake backing plate.
Pinion bearings can often be felt, if you push the pinion yoke to the side or up and down. Seal also often starts seeping.
Carrier bearings (and/or pinion) often change pitch in reverse.
Might want to have a look at the spider gears, if they overheat, the gears will often be rounded at the tips, instead of a sharp or defined edge.
Carrier bearings are pretty easy to check, with a medium pry bar. Get the bar in under the carrier (or ring gear) and lift. If you can feel, most any play, they are questionable. If they are bad, the carrier will flop around in there quit a bit.
I've had gear sets whine for 30-40,000 miles, one diff for 150,000. Unless they get really annoying, I just check for excessive bearing play and mostly ignore them, if they are healthy.
A couple of other things that will cause noise, is a chipped tooth or a really loose set-up from the factory, that is wearing toward unacceptable.
Liquid Moly gear lube, will often quiet them down by 50%, as will 140 weight gear oil.
Gear oil shears and gets thinner over the years (hey that rhymes). One reason synthetic gear oils are superior, they shear less. I work with many gear boxes, mostly industrial, but the theory is the same. We check gear oil for shear periodically, which is often a better indicator of the health of the lube, than age, usage or color.
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  #11  
Old October 28th, 2005, 08:37
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AZ Jeff AZ Jeff is offline
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Re: howl from rear

Bearing howl on "coast" is often the front pinion bearing. Bearing howl on "drive" is usually the rear pinion bearing. Either one of the usually causes pinion seal failure and leaks.

Carrier bearings are hard to spot, but 8Mud's idea of checking with a pry bar is as good as any method.

Wheel bearing related noise on a 8.25 are VERY hard to find by ear. On axles with tapered roller bearings out at the wheel, the noise increases when the suspect wheel is on the OUTSIDE of a high speed turn. On an 8.25, I found that is NOT the case, and wheel (axle) bearing noise is always constant, regardless of turning into or out of the defective bearing. An 8.25 rear wheel bearing will increase in noise steadily with speed, and will only lessen if the load is taken off the wheel (by jacking it up.) When my 8.25 wheel bearing failed (actually the shaft itself became brinnelled, and needed to be replaced), it was noisy as hell, but NO leaks at the seal.

Fortunately, wheel bearing issues are easy to visually confirm by pulling the axle shaft and examining that shaft and/or the bearings.
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  #12  
Old October 28th, 2005, 09:19
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Re: howl from rear

The only problems I've ever had with a 8.25, was over compressing the drive shaft and crunching the pinion crush sleeve (collapsible bushing or whatever it's called). Or maybe it was over torqued with the drive shaft at an extreme angle. It sure enough got noisy and the pinion pretty much flopped around in there and was really loose. The other problem was the lockig tab for the carrier bearing retainer (adjuster) came loose and allowed the bearing retainer to back out a bit.
AZJeff is right, I was visualizing a Dana and Chev diff, when posting. Forgot it was a Chrysler.
You might try wiggling (up and down) the axle a bit at the brake end. They usually have a few thousandths of play (hardly noticeable).
I do gears a lot, by feel.

Last edited by 8Mud; October 28th, 2005 at 09:45.
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  #13  
Old October 28th, 2005, 10:16
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DeftwillP DeftwillP is offline
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Re: howl from rear

I've always had a slight growl from the rear on 8.25 when letting off the gas at highway speeds. This past weekend, while putting in 4.10s and new bearings, we noticed that one of the carrier races had some pitting in it. Problem solved?

No. It still makes the noise at coast, but for only a second or two. Now with the different gears( and different operating rpms), it seems to lock right into the right rpm where it makes the growl even when in cruise and chugging down the highway. This is even after installing new bearings, front and rear, on the pinion.

My conclusion: Perhaps the rear ujoint. Otherwise, live with the fact the 8.25 is a noisy axle.
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  #14  
Old October 28th, 2005, 18:22
witstick witstick is offline
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Re: howl from rear

thanks for all the replys, i guess i will just have to live with it being noisy for now. Is there any kind of additive or oil i can add to the real that might quiet it down a little?? thanks alot,............... Chris.i
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  #15  
Old October 28th, 2005, 19:29
glub glub is offline
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Re: howl from rear

My D35 had vibes once. Mechanic said might be the pinion bearing. Luckily when he pulled the driveshaft, the u-joint fell apart. So that's all it was - the u-joint. I'd say replace it and see if that fixed it.
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