AU IRS diff, humming like a 747

BuckTooth · 19-05-2010, 03:17 PM

Hey guys and gals,

I don't have the faintest idea on what it could be so i'm asking the AU gurus for help.

I have a 2002 AU XR8, story is i've had to replace both the wheel bearings before, but now it has a terrible hum in the rear. I drove to griffith nsw, about 3hrs from home, I had 2 new tyres fitted to the rear of the car. I then drove home, 3hrs again, but when i reached the 50km signs on the edge of town and backed off i picked up a very loud hum in the rear end. It literally does sound like there is a jet in the boot trying to take off. I suspected maybe it was the new tyres so i did a front to back rotation but then upon road testing it the noise is still there and still very noticeable, How ever it is only from inside the car, i've driven past someone standing beside the road for me, and they heard nothing.

I pulled the 2 rear uprights of and tested the wheel bearings separately to the car and found no fault with them.

So just looking for suggestions on what to check next.

Cheers Doug

**Peuty** · 19-05-2010, 04:45 PM

When was the last time the diff oil was changed?

BuckTooth · 19-05-2010, 04:48 PM

I'm not sure, i haven't done it since purchasing the car and i've done 60,000km since i got it. I asked about the oil for it once but the local mechanic had no idea what to put in it.

**Peuty** · 19-05-2010, 04:55 PM

Penrite Limslip gear oil 85w/140 and penrite LSD additive is what I use

DW260 · 19-05-2010, 05:01 PM

What's the condition of the rear brake pads? They didn't take your car for a spin while you were waiting did they?

**Peuty** · 19-05-2010, 05:09 PM

Brake pads would only be noisy when brakes are applied. And you'd be able to hear it from the outside.

DW260 · 19-05-2010, 06:13 PM

Quote:

Originally Posted by Peuty

Brake pads would only be noisy when brakes are applied. And you'd be able to hear it from the outside.

They weren't in my girlfriends car; the roar was unbelievable. Turned out that one of the pads had worn down to backing plate, but the rest only down 50%. Anyway just a thought.

DW260 · 19-05-2010, 06:20 PM

Quote:

Originally Posted by Peuty

Brake pads would only be noisy when brakes are applied. And you'd be able to hear it from the outside.

They weren't in my girlfriends car; the roar was unbelievable. Turned out that one of the pads had worn down to backing plate, but the rest only down 50%. Anyway just a thought.

mik · 20-05-2010, 01:07 AM

perhaps its low on oil.

JK EX CHASER · 20-05-2010, 08:36 AM

Get the miss to jump in the boot and take for a road test to see which side the noise is coming from.

bigred · 21-05-2010, 11:15 AM

I have had that hum since about 200,000 km's. AU2 IRS.

Is ti a constant noise? I had a wheel bearing noise and it had drowned out the diff whine.

Might need a diff reco, let you know how I go this arvo when I get the car back, get the diff and bearings done.

BuckTooth · 21-05-2010, 05:12 PM

Yeah it looks like is the diff, so i'm thinkin it might be time to put the xr8 away till some more funds come up. I've got an AU wagon, its nearly done so i'm gonna drive that.

Cheers for the help guys and girls.

bigred · 21-05-2010, 05:48 PM

Give Northern Differentials a call, they seemed to be very fair price wise.

I'm picking my car up tomorrow full diff reco so car hopefully quiet as a mouse

BuckTooth · 26-05-2010, 03:12 PM

Just an update peoples,

Despite it only being 1 week old and having only done 1200km, the RH wheel bearing had failed again. So i grabbed another one, fitted it and problem solved.

Cheers for the help

bigred · 04-01-2011, 03:03 PM

Quote:

Originally Posted by bigred

Give Northern Differentials a call, they seemed to be very fair price wise.

I'm picking my car up tomorrow full diff reco so car hopefully quiet as a mouse

Sorry to dig up and old thread, but the car needing to go back to northern diffs soon for its first diff oil change since the rebuild has reminded me to post here.

All I can say is that the diff is whisper quiet after 10000 kms and its made a huge difference to the car.

Ended up having to get both bearings done as well, but its made all the difference.

Talk to Ben from Northern and he will sort you out. Gets the job done right.

Cheers
W