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2013 White Diamond sedan A6
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Discussion Starter · #1 ·
Sounds like my rear diff is making the dreaded whine/howl. I changed the fluid and it's no better at all. It also sometimes makes a bit of a clunking sound at very light throttle when coming from a stop and other times in slow parking lot type turns. Any advice from where to get a reasonably priced rear end? Cadillac dealership wanted over $6K to get and install. Pffft! No way. Also if I continue to drive it like it is will I damage anything else further and wind up spending more?
 

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Rear end can cause catastrophic damage to your vehicle, and if it goes completely fucked and locks up on you while doing 80mph on the interstate, you do the math.
You can get OEM for 3k or whatever they charge forbit nowadays, and it should take you 6 hours to a full day to install, depending how on your skill set. Or dop ~8k on Gforce 9in rear end that comes with everything needed, is bullet proof, but the price is obviously up there.

Edit: check the diff bolts (one in the rear middle and 1 on each side), I can't remember the tq specs, but they could just not be tight, and have some wiggle.
 

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Discussion Starter · #6 ·
Rear end can cause catastrophic damage to your vehicle, and if it goes completely fucked and locks up on you while doing 80mph on the interstate, you do the math.
You can get OEM for 3k or whatever they charge forbit nowadays, and it should take you 6 hours to a full day to install, depending how on your skill set. Or dop ~8k on Gforce 9in rear end that comes with everything needed, is bullet proof, but the price is obviously up there.

Edit: check the diff bolts, I can't remember the tq specs, but they could just not be tight, and have some wiggle.
There goes the cam and trunnion upgrade budget :(
 

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You could be good, just get a torque wrench and re-torque the bolts. Most of our diff's are noisy, so unless it starts clunking while driving and/accelerating, you should be OK.
Also, change your diff fluid like every 2-3 oil changes, or less. I do mine every oil change.
 

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Discussion Starter · #8 ·
You could be good, just get a torque wrench and re-torque the bolts. Most of our diff's are noisy, so unless it starts clunking while driving and/accelerating, you should be OK.
Also, change your diff fluid like every 2-3 oil changes, or less. I do mine every oil change.
Thanks for the heads up on that, do you happen to know the TQ spec for those bolts?
 

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The service was performed by Cadillac and I was assured the fluid used was the GM fluid that included the friction modifier.
It has been established that this is a TERRIBLE assumption. Multiple folks have found the dealer failed to use the additive. Get with the dealer for the part number used… OR, have the couple ounces of additive… added
 

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Discussion Starter · #12 ·
It was not assumed, I deliberately inquired specifically about the LSD friction modifier that was to be used. The rep stated the GM fluid contained said additive in question.
 

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There goes the cam and trunnion upgrade budget :(
Man, I was in the same boat just 2 weeks ago with my '14 sedan. I've been hearing noise from the diff and the drive shaft for months now. The $5500 I had planned for performance mods went to the drive train instead. Oh well, perhaps next year. I had a performance shop in my town put OEM parts back in because that's what they would warranty and I don't plan on putting her on the racetrack.
 

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Discussion Starter · #16 ·
Man, I was in the same boat just 2 weeks ago with my '14 sedan. I've been hearing noise from the diff and the drive shaft for months now. The $5500 I had planned for performance mods went to the drive train instead. Oh well, perhaps next year. I had a performance shop in my town put OEM parts back in because that's what they would warranty and I don't plan on putting her on the racetrack.
Damn $5,500 for a rear end replacement?! I think it’s time I get some proper jack stands and dust off the toolbox.
 

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I wouldn't expect whine to ever be improved by a fluid change. The fluid change helping noise is more for the cold low speed growl when turning. Debating whether or not the dealer actually put friction modifier in if there isn't any noise of that nature is pretty futile.

Lots of these things are driving around with whine, the chance of it just locking up while going down the highway is low. That said, driving it isn't going to cause additional damage to anything you won't be replacing anyway since you'll be pulling the whole unit and swapping it. It's a matter of your tolerance for putting up with the noise it makes.

I'd put a cooler on the new diff though. Even if you aren't tracking it. These diffs run hot. It doesn't take long nor does it take an incredibly hot day for mine to get up to the temp the pump kicks on at.
 

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I wouldn't expect whine to ever be improved by a fluid change. The fluid change helping noise is more for the cold low speed growl when turning. Debating whether or not the dealer actually put friction modifier in if there isn't any noise of that nature is pretty futile.

Lots of these things are driving around with whine, the chance of it just locking up while going down the highway is low. That said, driving it isn't going to cause additional damage to anything you won't be replacing anyway since you'll be pulling the whole unit and swapping it. It's a matter of your tolerance for putting up with the noise it makes.

I'd put a cooler on the new diff though. Even if you aren't tracking it. These diffs run hot. It doesn't take long nor does it take an incredibly hot day for mine to get up to the temp the pump kicks on at.
Which cooler are you running? How do you know the pump is kicking on, can you hear it?
 

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The fluid change helping noise is more for the cold low speed growl when turning. Debating whether or not the dealer actually put friction modifier in if there isn't any noise of that nature is pretty futile.
In post #1, OP stated "clunking sound at very light throttle when coming from a stop and other times in slow parking lot type turns" which precisely points up the additive issue. That's why I asked if the proper fluid install was verified.
And yes, it has nothing to do with the whine, as stated.
We agree.
A side note: I bought the new GM diff through RA last year...and it had a slight amount of whine, fresh out of the box. It isn't much, but it also isn't zero as it should be.
 
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