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Hello everyone, my neighbor just bought a very nice 2011 CTS 4WD with a bad front differential for very cheap and I am going to fix it for him. I am wondering what exactly the procedure is for replacing the front diff. I looked at it and I know that I will need to remove the CV axles and front driveshaft, but I am not sure whether I need to remove the sub frame to get the diff out, looks like I might. So if anyone has done this job or knows the procedure or an easier way of doing it I would really appreciate you letting me know, it looks like taking the sub frame down would be a pain on this car and I would rather avoid doing so if possible, but if that's what I need to do that's fine. Thanks in advance, I really appreciate any advice or suggestions!
 

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Discussion Starter #2
For those of you who are wondering, I have an update. Yes the sub frame does need to come down, but not all the way. I dropped the sub frame about 5 inches on the passengers side where the diff is and lifted the motor up a few inches and I was able to get the old diff out and the new diff in without disconnecting anything from the sub frame other than the steering rack and the motor mounts. I didn't have to lift the motor up enough to require removing the strut bar.

Here's a few tips to anyone who is going to do this job:
1. Lift the front of the car up as high as you safely can, it makes this job a lot easier.

2. The axle shaft that goes through the oil pan comes out, I needed to take it out to have enough room to get the diff in without completely removing the sub frame. Take out the 3 15MM bolts around the plate around where the drivers side CV axle goes into the oil pan and (carefully) whack the other side of the shaft with a hammer, that will push it towards the drivers side and get it out of the way. Once you get the new diff in, just tap the shaft back into the diff from the drivers side and reinstall the 3 15MM bolts.

3. Make sure the sub frame is lined up correctly before reinstalling all the bolts. All the mounting holes must line up, the motor mount holes must line up, and the bottom of the radiator must be sitting in it correctly. Make sure the top of the radiator is still in its mounting brackets too. Once you get it lined up and get all the bolts back in, tighten them a little at a time evenly to prevent it from binding. Do not fully tighten any of the bolts until they are all in. I would say that lining the sub frame up again is the hardest part of this job, especially if you are doing it alone like I was.

4. While everything is apart, inspect other parts for damage like the CV axles, motor mounts, and suspension parts, easier to replace it while everything is apart than to have to take it back apart again. My neighbor's CTS ended up needing ball joints and motor mounts as well, so I did that too while it was apart. If you are installing a used diff it wouldn't be a bad idea to replace the axle seals before you install it to prevent leaks.

5. Make sure the car is level when you fill the new diff with oil. If it isn't level you risk overfilling or underfilling the oil, both of which can cause damage and shorten the life of your replacement differential.

6. As always, take your time. Especially doing a job like this, rushing could result in damage if you force or forget something, so don't try to do this job in a hurry because it likely won't end well.

I hope this information is helpful to someone since there isn't much information available on replacing the front diff on these cars. Any questions feel free to ask :)
 

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**2014 CTS4 Sport Wagon-Luxury**
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sounds like you had quite a job on your hands...were you able to determine what caused the front differential to need replacement???...I think your posts may be the first report of replacing a differential I have read.

thanks for sharing...

Bill
 

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Discussion Starter #4
sounds like you had quite a job on your hands...were you able to determine what caused the front differential to need replacement???...I think your posts may be the first report of replacing a differential I have read.

thanks for sharing...

Bill
I am not sure what caused the failure, possibly a defective casting or abuse. The whole piece that the driveshaft connects to is broken right off, but maybe the failure was caused by low fluid. Before I removed the old unit I pulled the drain plug to drain whatever oil was left in it so I didn't make a mess and there was nothing in it, literally not one drop came out. Whether the oil leaked out and caused the failure or the oil leaked out as a result of the failure I have no idea. I will take and upload pictures of that broken differential later.
 

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These are the posts that make forums worthwhile; pics will be the icing on the cake.
Thank you for the share!
 

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Discussion Starter #6 (Edited)
Unfortunately I didn't think to take pictures of the replacement process, I wish I did. However, I do have these pictures of the old differential.
 

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**2014 CTS4 Sport Wagon-Luxury**
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thanks for sharing what you already have...

Bill
 

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'12 CTS Performance Sports Wagon AWD
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Makes sense then why the transmission shop told me it could be $2000 to replace the seal on the differential... I believe I have a leak on my front differential but not sure where exactly.

Sounds like a major job. Maybe just topping off the fluid for now will be good enough...
 
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