How to distinguish between rear end noise and tire/road noise?

boostfrk

10 Year Member
Aug 30, 2011
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Colorado
Since I got a quieter exhaust on my '90 5.0 hatch I can notice a low growling noise (for lack of a better term) coming from the back of the car. It seems most noticeable at lower speeds, but perhaps that's just because everything else isn't as loud. I can hear it best if I turn my head and look out the passenger window (ie: through my right ear).

Since it's a hatch I imagine NVH is transmitted more into the cabin from the rear end. I have UPR's rear upper and lower control arms, as well as all new shocks/struts within the past 100 miles.

How can I distinguish between a problem noise from the rear end and just regular tire/road noise? The tires are pretty well worn, so it's not unreasonable to think the noise is coming from the tires. I just want to make sure there isn't a bigger problem I need to take care of. Is the only way to test this buy new tires and see if it goes away?

I imagine jacking the rear of the car up, setting it on stands, and CAREFULLY running it through first and second gear wouldn't help. I would think the rear end would may behave (and sound) differently when subjected to a load as it is when it's sitting on the ground.
 
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Well to try to rule out tire noise I would try a couple of things, try driving the car on a different road surface, gravel or blacktop and see if it goes away or changes also try overinflating them temporarily and see if it changes but be aware that overinflating could cause safety issues ,blowout etc.........
also try to listen to see if the noise stops or changes when making turns. Or could you possibly borrow another set of tires from a friend .

I would lean towards a bad axle bearing
 
Does the sound change on accel, float, or decel-or is it always there? Growling noises are no fun...mine has a not so nice little roar to it...last guy I had listen to it said I might have a pinion bearing with incorrect preload...possibly from the idiot corksoaker that set up the axle with new parts supplied by me...


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Does the sound change on accel, float, or decel-or is it always there? Growling noises are no fun...mine has a not so nice little roar to it...last guy I had listen to it said I might have a pinion bearing with incorrect preload...possibly from the idiot corksoaker that set up the axle with new parts supplied by me...


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Sounds like it's pretty much always there regardless of accel, float or decel. Of course it's easiest to hear it when I'm at a steady speed, probably because the engine noise is constant, etc. The only exception would be in first gear. If I'm driving through a parking lot let's say, run it up to 2,500 or 3,000 and then let off the gas and engine brake there is a higher pitched whine/growl, but it comes from the drivetrain area in general, not just the rear end. This seems to be somewhat typical though with any manual transmission car; I figured mine was just louder because the car is 20 years old.

I hope I don't have to have the rear end re-built, although if I did it would be a good excuse to put in new gears. Anyone know a good shop to do this around the Cape Canaveral, FL area? Worst case would be to take it to Orlando, which is about 45 minutes from me.
 
In my experience gears that are set up incorrectly (whether the noise be on accel or decel) usually will whine as opposed to growl. usually a wa,wa,wa,wa sound. could be a pinion bearing, carrier bearing but I would check the axle bearings first.
 
In my experience gears that are set up incorrectly (whether the noise be on accel or decel) usually will whine as opposed to growl. usually a wa,wa,wa,wa sound. could be a pinion bearing, carrier bearing but I would check the axle bearings first.

Well tires are up next. I'll replace those and see if the noise decreases, otherwise maybe I'll replace the axle bearings just to rule them out. I read up a little bit on them and it didn't seem to be too hard.

I certainly don't have a whine, and I don't have a wa wa wa wa sound (ie: a cyclic sound)