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'04 1SC CTS
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47 Posts
Discussion Starter · #1 ·
My 2004 FE3 CTS has 106K miles, and I'm finally getting tired of listening to the rearend noise at all speeds above 10 mph.

When i had my '96 Camaro a few years ago, I built my own 9-inch rearend, including setting up the gears and running a pattern. I had no whine. I have all the necessary tools (hydraulic press, depth gauge, gear paint, etc).

I've seen some rear differential assemblies selling for about $300 on eBay, and I'm really starting to think about buying one and swapping it in my car this summer. Obviously a junkyard rearend is prone to have the same kind of whine. At the very least I think I'd buy new axle seals and gaskets, then open up the carrier assembly and at least run a pattern and check for proper backlash.

My only reservation with going the "used" route is the fact that Cadillac doesn't have the same DIY oriented target market as Ford does when it comes to rear ends. For example, you can easily find 9" ring and pinion kits. Not so sure about how easy it would be to find those for the CTS.

Does anybody have any feedback on this? What would it cost me to buy a new assembly from GM (assuming that I'd install it myself)?

Thanks!
 

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06 Cadillac CTS 3.6L [Sold :( ] 02 Mustang GT 5Spd
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1,161 Posts
I don't know much about the mechanical aspect of this but you maybe better off getting an LSD out of an STS. As far as I know they bolt right in and I haven't heard of any issues with them.
 

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Cadillac
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120 Posts
My 2004 FE3 CTS has 106K miles, and I'm finally getting tired of listening to the rearend noise at all speeds above 10 mph.

When i had my '96 Camaro a few years ago, I built my own 9-inch rearend, including setting up the gears and running a pattern. I had no whine. I have all the necessary tools (hydraulic press, depth gauge, gear paint, etc).

I've seen some rear differential assemblies selling for about $300 on eBay, and I'm really starting to think about buying one and swapping it in my car this summer. Obviously a junkyard rearend is prone to have the same kind of whine. At the very least I think I'd buy new axle seals and gaskets, then open up the carrier assembly and at least run a pattern and check for proper backlash.

My only reservation with going the "used" route is the fact that Cadillac doesn't have the same DIY oriented target market as Ford does when it comes to rear ends. For example, you can easily find 9" ring and pinion kits. Not so sure about how easy it would be to find those for the CTS.

Does anybody have any feedback on this? What would it cost me to buy a new assembly from GM (assuming that I'd install it myself)?

Thanks!


I have an open Diff from my 2006. It has the upgraded pinion seal and is vented. It had about 40k on it when I replaced it with a LSD. Unlike a junkyard Diff, I can tell you that it was totally quiet and never leaked a drop. I did ding an Axle seal when I was removing the diff, it should get a new one. You can have it for $225 shipped. ( BTW, the stock LSD Diffs are kinda weak and prone to clunking noise, I almost wish I left mine alone)
Don
 

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2004 cts sport
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856 Posts
i took my original apart not worth it to rebuild it.. get one from a scarpyard or somethign and get a warranty just incase... change out the seals which should run you $150
 

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'04 1SC CTS
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47 Posts
Discussion Starter · #5 ·
Gaetano,

When you say "not worth it", do you mean that the parts to rebuild the reared are really expensive? Can you elaborate?

Thanks
 

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Cadillac Technician
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11,051 Posts
AFAIK the problem with the differentials making noise is a case related issue.
I have never seen one rebuilt that solved the problem.
I don't think there are many parts out there to modify it and it isn't like the old 9 inch where you can shim here and there to get a good pattern.
We just replace the whole unit when they go bad.
 

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2006 CTS-V
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4,969 Posts
I'd go with a 9" rear if you were redoing the whole thing anyway. The CTS-V guys have done it quite a few times and I'm sure its a stronger diff either way.
 

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37,297 Posts
AFAIK the problem with the differentials making noise is a case related issue.
I have never seen one rebuilt that solved the problem.
I don't think there are many parts out there to modify it and it isn't like the old 9 inch where you can shim here and there to get a good pattern.
We just replace the whole unit when they go bad.
:yeah:

They call it "hypoid howl". Replacing the innards with all new components probably would not even get rid of the noise.

As for the V, its diff was borderline. When my CTS-V diff started making noise, they didn't mess with it. They just replaced the diff. But the regular CTS does not have this issue, for the most part.
 

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2004 cts sport
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856 Posts
like ewillard stated the best route is to replace it, seals alone would probably run you 200-300 $$. if you are planning to do this yourself and have some time and knowledge to spare by all means, but i wouldnt
 

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2006 CTS-V
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4,969 Posts
I heard the STS were direct bolt on and had LSD? Not 100 on it, but thats what i've heard
 

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Cadillac
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120 Posts
Yes the STS is a bolt in. I have an 05 STS LSD in my car. Its not a very strong LS, with one wheel off the ground it only takes about 25 lbs of pull on the tire to get it to rotate. I've had 2 of them in my car and both were exactly the same (the pinion bearing failed within 15000 miles on the first one-thank you Lucas Synthetic gear lube-junk!!) They can also be difficult to make run quiet, I still get a tiny bit of clutch groan with Amsoil severe gear oil. Overall probably not worth the bother unless the diff is bad to start with. if I had left the perfectly good open diff in the car I would have $800-1000 more in my pockets today.
 

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Cadillac Technician
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11,051 Posts
I know of no viable street worthy replacement.
The CTS uses a cradle mounted stationary differential assembly with independent suspension.
The replacement would have to fit in the same opening, mount in the same points and have correct input and output mechanisms.
All the attempts that the V guys have made require extensive modifications to the frame, exhaust, suspension, or drive axles all of which is cost prohibitive.
Most older cars that let you "swap in a 9" had a fixed housing that was on coil or leaf springs, not mounted the way the CTS is.
It will be a long and painful, not to mention expensive, process if you go toying with it to "save money". I am certainly saying it is not possible, but from my personal viewpoint it would be pretty wasteful and just outright silly to do.

G80 is limited slip, all variants of these that will "fit" have those with or without G80.
If you get a G80 rear be sure to install the friction modifier and be sure that the gear ratio matches that of the existing one or you will have other problems.
 
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