loud rear end

[dlb]

i've got reggie (the project car) almost done and have taken him for a few test drives and so far no major problems but the rear end is super loud once i get up to 60+ km/h. i used to think this was caused by road noise coming in the gaping holes in the rear wheel wells but i've dealt with those (pretty funny, will post pics when it's all done) and the sound persists. the car has regular all seasons on it so it's not excessive road noise from aggressive tire treads. i just checked the rear diff fluid level and it's fine but i will drain and replace it tomorrow anyway just to rule it out. it doesn't sound like a bearing because it's more of a hum--definitely not a grind/growl/screech. it can be heard a bit at lower speeds and gets louder with increased speed.

does anyone have any other suggestions on what i might check?

[xirdneh]

probably axle bearings
have someone drive while your in back seat
if it sounds like one side is louder than the other that would be it
i have opened the door and stuck my head out but that is dangerous
would be better to hang out window

[dlb]

i'll try that tomorrow. are axle bearings different than wheel bearings? sorry, i know that sounds like a noob question.

[Lil Beast]

It's definitely a bearing(which one dunno!), they can do a humming winding sound! And yep the axle bearing are the same than the wheel bearing! But it could be a bearing in the diff too!

[dlb]

i got my wife to drive while i rolled around in the back and it sounded like it's coming from the passenger side. i'll get her to help me again though, just to be sure.

[smokerx]

Might be tailpipe or muffler. Etc. vibrating against the Frame. I've seen various fire resistant rubber matting such as flaps of tire tread shoved in various places to prevent vibrations on motor bicycles; as they get very noisy and shaky in the mounts and exhaust and sound as you describe. Tailpipe is also passenger side and ,lol, don't get under the car and rev it to check . I think I remember some noises back there when I had a tailpipe and muffler. must have rusted off on the highway,,,

[dlb]

the exhaust pipe comes off the engine on the passenger side but crosses over to the driver side mid-way down the vehicle. good idea though, thanks.

[Jarf]

DLB - Usually, an internal diff issue (side or pinion brgs), will usually emanate as more of a whine, more often on deceleration or steady cruising and will be worse in 4wd than 2wd.
(diff under load)
You are likely into an axle bearing but it would be worth rotating tires (fr to back) and see if the noise moves.
Tires can produce a huge amount of road noise without having "aggressive" tread, a little cupping on the inside edge can produce a remarkable amount of rumble.

If you run your hand over the tread face (start at the forward side and slide your hand over the tread face towards the rear, so that you are feeling the tire as the road does)
you will get a good idea of how smooth the wear is, if it feels a little lumpy, it WILL cause road noise.
Rotating the tires is about the only way to be sure though.

Failing that, get it up on stands and run it in 4wd and listening with a stethascope, then you will know FOR SURE where the noise is coming from.
Pay close attention to the pinion area and where the axle tubes meet the pumpkin.
If you do find the noise to be centered around the pumpkin, look for some "molyslip" diff and gear treatment, stuff is magic but very hard to find.

My money would be on axle bearings, though.

[dlb]

rotated the tires and drained/refilled the rear diff but the problem persists. i'm glad i did the diff though because i was surprised at the size of the chunks that were stuck to the plug magnet:



i pulled the biggest pieces off and wiped the gear oil away to show how big the shards are. might not look like much here but when you think about these guys floating around all the spinning gears, gouging and grinding and damaging everything, you realize that it was a good idea to change your diff oil.



i like your idea about putting it on stands to get a good listen, jarf. my wife will hate you for volunteering her to help me with this but i'm grateful.

[turdsmell#2]

DLB, I hve dealt with this twice, both time it was the axle bearings.

[dlb]

question: can the rear axles be swapped between left and right or is the gearing on the inner splines different? i ask because the driver side rear axle on my parts car is good but i suspect it is the passenger side rear bearing that is making the rear end loud. if i can just swap them that will save me a trip to the store and some work.

[Petros]

The axles are different lengths, i do not think it is possible.

[Petros]

looks like something is coming apart in the rear axle. If it is the bearing I suggest when you have the rear axle out, you drain the diff and flush a lot of solvent through the axle housing to drain it all out. Pour the solvent in through the axle end where the bearing failed, and allow it to drain into a pan under the diff housing. There is likely much more metal shavings in the axle housing. Than put the plug back in the housing, fill the whole axle housing with solvent, spin the rear diff round and than drain it out again.

Even with a new bearing you could trash the diff with that much metal floating around in the diff. Get as much of it out as possible now to save you grief later. IF you really want to be sure to clean out the axle housing, you can pull the other axle shaft out, and than pull the diff third member out of the center. Than you can clean the whole axle housing out from the large opening on the forward part of the diff housing. Than you can also wash and blow off the diff assembly itself. Not likely you need to go to that much trouble, but it would be the safest way to make sure all of the metal particles are cleaned out.

[xirdneh]

the two rear axles are the same length
the difference is the cover plate that has the 4 holes in it for the studs to pass through
they have a bulge on the bottom to accomodate the weep hole in the brake plate
the bulge has to be on the bottom and aft when installed

if you install the wrong way the bulge will be on the bottom and forward
the weep hole will not be able to weep
and water cannot get totally out
water level could go as high as bottom of hole in plate for axle
that would probably cause bearing to fail sooner that it should
i have installed axle this way on purpose but only as a temporary fix until bearing is fixed on proper axle setup

[dlb]

looks like something is coming apart in the rear axle. If it is the bearing I suggest when you have the rear axle out, you drain the diff and flush a lot of solvent through the axle housing to drain it all out. Pour the solvent in through the axle end where the bearing failed, and allow it to drain into a pan under the diff housing. There is likely much more metal shavings in the axle housing. Than put the plug back in the housing, fill the whole axle housing with solvent, spin the rear diff round and than drain it out again.

i carefully examined the drained diff oil looking for more chunks or grit but found nothing else, peter. that doesn't necessarily mean the diff is grit free and i agree it's probably a good idea to flush it but it appears that the worst of it was stuck to the magnet.

when you say to flush it with solvent, do you mean generic stuff called 'solvent' that i can get at any hardware store or is there anything in particular i should use?