Drivetrain Rear Differential Noise

Chenn2389

Member
Apr 30, 2020
3
1
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31
Arizona
Hey, I am a new member and this is my first post. I purchased a 1994 gt project car that I have been working on for the past 5 months. The car has 104k on the dash. So far I have started out by getting the chassis and drive line ready for more power. In the front I have replaced the rack and pinion, tie rod ends, front control arms, bushings, ball joints, struts, springs, hubs, rotors and pads. In the rear I have replaced upper and lower control arms, upper axle bushings, quad shocks, shocks, axle bearings and seals, differential fluid and motocraft friction modifier, rotors and pads. New Nitto NT555 G2 tires all around 275 in the rear 245 up front.

Now that everything is back is spec and suspension slop is gone I am getting howling/grinding noise coming from the rear end. The noises only comes turning sharp right at low speeds or taking a smooth banked turn to the right. The sound only happens while coasting or having the clutch depressed. It’s a complete mystery to me. I took it to AZ Differential Specialists two days ago and had them drive it. They were unsure of what it was. The gave me another bottle of friction modifier and told me to put it in the diff and then over fill the pumpkin until it leaks out and they didn’t charge me anything. I tried this 2 days ago but did not help. I have driven the car 30 miles since then and the symptoms haven’t changed. Tires are perfectly balanced and the alignment is dead on. I am stumped as to what’s going on.

I am getting my fresh top end back from the machine shop on Friday. Edelbrock performer 170cc heads and Edelbrock performer upper and lower intake. I want to get these issues with the rear end fixed before I send more torque through it.
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revhead347

Just rub Vaseline all over
15 Year Member
Jun 14, 2004
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So basically when the axle is not under load, it's making noise. That's not good. I doubt you'll figure it out until you get the differential cover off and look. Check to make sure the driveshaft bolts haven't come loose or something like that first.

Kurt
 

jozsefsz

Mustang Master
Aug 11, 2013
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Even though new, I'd suspect one of your rear wheel bearings. Was it howling before you changed those? 100k miles isn't a lot, I'd suspect the originals were ok. It's possible to damage one on installation and get all kinds of noise. Other things to check are the U-joints, I've had one bind almost completely due to old grease drying out. Last thing I've had create weird howling and noise (which seemed to come from the rear) was the transmission fluid. The old ATF breaks down from just sitting. If you haven't replaced that in a while, it doesn't hurt. You could also have something going wrong in the diff itself - as revhead mentions. Pinion bearing, too little endplay in the diff setup, etc. If someone cranked down on the pinion nut at some point to help fix a leaky seal, that could be the problem.
 

revhead347

Just rub Vaseline all over
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Acworth, GA
I don't know. If it happened right after the axle fluid change, then I would guess that it's something in the pumpkin. Axle bearing would be making noise all the time. U-joints are possible. The description indicates to me that the locker isn't unlocking properly, which has to do with the fluid.

Kurt
 

Chenn2389

Member
Apr 30, 2020
3
1
13
31
Arizona
I don't know. If it happened right after the axle fluid change, then I would guess that it's something in the pumpkin. Axle bearing would be making noise all the time. U-joints are possible. The description indicates to me that the locker isn't unlocking properly, which has to do with the fluid.

Kurt

Thanks Kurt,

I suspect the clutch plates, carrier bearing, or spider gear on the drive side axle of the limited slip has gone bad since that the side that gets loaded turning right. It did make the noise prior but got much worse after I changed the fluid and axle bearings and all the suspension.
 

Chenn2389

Member
Apr 30, 2020
3
1
13
31
Arizona
I took a video this morning. This is on a cold start going 10 mph down the street. It gets much worse when it’s warmed up and been driving for ten minutes. The manager at Arizona Differential drove it this morning said the carrier is loose. Gonna replace the carrier and pinion bearings and clutch plates over the weekend and I‘ll have it Monday.

View: https://youtu.be/6uivLlrj4SQ
 

revhead347

Just rub Vaseline all over
15 Year Member
Jun 14, 2004
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Acworth, GA
Video is great. If you have everything out, might as well change the wheel bearings while it's apart. When those go bad, they ruin the axles.

Kurt