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Discussion Starter #1
My rear end blew out and I made a huge mistake of taking it the transmission shop that had recently rebuilt the rear end in my Avalanche vs. to my regular BMW guy. Dumb, dumb, DUMB.



Anyway, I had them install a Turner LSD. After I got it back I am getting a horrible drone above 60 MPH with it really bad around 75. It has a slight vibration too. The source of the drone seems to be coming from the front of the car. When I took it in for the follow up they replaced the driver side rear axle (which I replaced 14,000 miles ago). He also said he thought it was the front wheel bearing which I also replaced 14,000 miles ago. Luckily I caught him before he installed them and I replaced them again. Long story short, it made no difference. The guibo looks solid and it looks like it was hooked up right based on the arrows. Any ideas what the probable source might be?



Thanks,
 

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My rear end blew out and I made a huge mistake of taking it the transmission shop that had recently rebuilt the rear end in my Avalanche vs. to my regular BMW guy. Dumb, dumb, DUMB.



Anyway, I had them install a Turner LSD. After I got it back I am getting a horrible drone above 60 MPH with it really bad around 75. It has a slight vibration too. The source of the drone seems to be coming from the front of the car. When I took it in for the follow up they replaced the driver side rear axle (which I replaced 14,000 miles ago). He also said he thought it was the front wheel bearing which I also replaced 14,000 miles ago. Luckily I caught him before he installed them and I replaced them again. Long story short, it made no difference. The guibo looks solid and it looks like it was hooked up right based on the arrows. Any ideas what the probable source might be?



Thanks,
Yep, the backlash and pinion depth are probably not set up correctly which causes the noise in the rear diff.
 

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Discussion Starter #3
Yep, the backlash and pinion depth are probably not set up correctly which causes the noise in the rear diff.
Thanks. I'll either have them check that or take it to my BMW guy like I should have done in the first place.
 

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First, make sure the csb is preloaded forwards, and then loosen the center driveshaft gland, give everything a good wiggle, and then retighten.

A diff does not drone, usually- it'll whine, howl, sizzle or grind, depending on how it's mis- set. I'd be far more suspicious of the driveshaft, since it would have
been pulled and reinstalled by a non- specialist. It may also have a binding u- joint.

If it's a high- frequency vibration (way over what you'd get with a tire) it's almost guaranteed to be driveshaft.

hth

t
 

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well first thing that comes to mind when saying you have noise after putting in a LS diff is the diff. gear builder doesn’t set r & p perfectly you’re gonna get noise. limited slip unit same thing.

but you said the drone is from the front. so that doesn’t fit. so I suggest you pinpoint the area of the drone and proceed after that.

it could certainly be the something in the driveline, but that usually has vibration issues related.

and then who knows if they messed with your exhaust hooking up your diff and driveline? this is much less likely as it would be more heard.

curious did you get your gear ratio switched too? something shorter and not as tall?
 

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You're going to need to diagnose where the noise is coming from and then why.
Driveshafts are pesky noise transmitting tubes and have the ability to take a differential noise (if that's the issue?) and send it very far forward.

You can test it at home, but it's dangerous. Raise up the car onto jackstands with the rear suspension compressed. Run the car in gear and get to the 'zone" where the noise happens and gather clues. Running the car with the suspension drooped will stretch the rear axles and A) put unwanted force on the bearings/cages. B) produce false conditions for testing.
Should at any point it fall off of the jackstands...........

I see you're in Cincinnati. Brett Anderson of Koala Motorsport builds hundreds of differentials, albeit the Turner one you have is from another guy. You will likely counter some resistance if you seek out his diagnosis. Albeit supremely qualified to do so.
 

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Discussion Starter #7
Thanks all. While not a BMW specialist, the shop is a transmission/drivetrain specialist. The only reason I took it to him is because they did a good job on my Avalanche rear end and I noticed an E46 in their lot when I was picking it up. The LSD was bought as a complete unit (housing and all) from Turner Motorsports.

TobyB - Thanks. I was thinking either guibo or center support bearing as well.

Alex325ci - I'm sure it's not the exhaust. That thought did cross my mind. To test it, I got it up to 70 and once the drone was really going, I took it out of gear and let off the gas. The drone only fluctuates with rotation, not with engine speed. Oh, and yeah, I did switch to a 3.46 gear ratio. I wanted something with a bit more pep without killing fuel economy.

MrMCar - Thanks. I thought about what you mention regarding testing on jackstands but I don't have the guts to try it. This is an argument to get a full lift (jk).

I'll see if the CSB is something I feel comfortable with. If not, I may give them one last chance to make it right or do what I should have done initially and take it to my regular BMW guy.
 

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like I said, you’re going to have to pinpoint the area of “drone”.

I don’t have the car in front of me but my money is on the new 3.46 LSD.
 
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