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howl from rear

witstick

NAXJA Forum User
Location
Lebanon, PA
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?
 
witstick said:
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?
 
Fergie said:
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.
 
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.
 
'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
 
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.
 
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.
 
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.
 
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.
 
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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.
 
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
 
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.
 
witstick said:
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
Ok, you posted a question and a lot of opinions were offered by people who have not seen your jeep, not heard the howl and so on. This is the point where you go and you crawl underneath and push up on the pinion to see whether there is play in it, maybe drain the fluid and try the prybar trick to see if there is any play in the carrier bearings and so on. This is not a point where you take opinions offered by others as diagnosis as though it was performed on the spot (or at least that's my opinion).

Anyways, I'll get of my :soapbox: now.
 
I am going to go crawl under it and check things out, just didnt get out to do it yet.......sorry i am new to this jeep thing. I just thought that maybee if it is known to be a noisy axle i could add some oil additive to it to help. Anyhow i going to check it out before i post again...
 
Kejtar said:
Ok, you posted a question and a lot of opinions were offered by people who have not seen your jeep, not heard the howl and so on. This is the point where you go and you crawl underneath and push up on the pinion to see whether there is play in it, maybe drain the fluid and try the prybar trick to see if there is any play in the carrier bearings and so on. This is not a point where you take opinions offered by others as diagnosis as though it was performed on the spot (or at least that's my opinion).

Anyways, I'll get of my :soapbox: now.
Come on Kejtar, you know that some of us can diagnose ANY problem without ever actually seeing or hearing the vehicle. I KNOW I CAN!!.
:jester:
 
The thing about drive train noise is, the sound travels and often sounds the loudest, far from where the actual problem is. Localizing it is often hard, sometimes putting it on a lift and listening from underneath while it's in gear with the brakes slightly applied, can help find it. Sometimes it takes the weight of the vehicle on the bearing to make it noisy.
I've been fooled too many times and/or seen other guys get fooled and replace parts unnecessarily. A couple pop to mind, one bearing howl had most everybody convinced it was a rear wheel bearing. It finally turned out to be a rear tranny bearing.
Just a couple of months ago I was convinced I had a noisy front transfer output bearing, which turned out to be a the right front hub. It sure sounded like it was coming from the transfer.
Sounds dumb, but drive train noise has fooled a whole lot of very experienced guys.
All you can do is check the most probable first, then work down the list.
I've found driving by a brick wall, with the windows open and a passenger with good ears to help, often helps localize to source of the noise.
 
This is an OLD thread but I was searching for the same answers. Our '01 XJ with 150,000miles has the Chrysler 8.25 rear end and howls at 30-35mph while holding a steady throttle. Let off and it goes away. This usually occurs only once warmed up. Starting from cold it takes a few miles before this begins.

I'll be looking for another XJ 8.25 in the junkyard to open up and refurb. If I'm lucky it will also have 3.55 gears.

Weekender

Weekender
 
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