[Susan_C]

I have a 2009 CTS with AWD and 139k miles. I started having a loud popping sound and jerking feeling which feels like it's coming from the front when backing or turning the wheel at slow speed, mostly after driving for a few minutes. Took it to a GM dealer who said the rear differential needed a fluid change. They changed the fluid and said to drive it a little and it should work itself out. They also said there was no shavings or debris in the drained fluid.

Drove it a couple of days and called GM dealer to tell them problem wasn't solved. They had me bring it back and after 2 days, told me they couldn't diagnosis the issue because they needed "special tools" that only a Cadillac dealer would have. Took it to the Cadillac dealer who after keeping the car over night said the "transfer case" needs replaced because it "locked up."

Remember...it only does it when turning the wheel (left or right) and when backing. Drives down the road fine. No other symptoms. No warning lights on. No leaks. New tires put on a couple of months ago. I had a 2005 SRX that locked up the transfer case, and when it did, the car stopped dead in it's tracks and made a horrible sound it you tried to move the vehicle at all.

I'm just not sure it's a transfer case issue and I don't want to keep paying for diagnoses and "repairs" to have the same problem. Anyone else have this issue?

 

[AAIIIC]

Moved from the CTS-V forum to the CTS forum. I'm sure your fellow CTS4 owners can offer some suggestions.

 

[Long]

Welcome, Susan_C-- sorry to hear of your recent troubles.

If you expressed originally that the noise you were hearing was coming from the front of the vehicle, I'm not certain why a rear differential service was performed. I'm equally uncertain of what tools a Cadillac dealer would have exclusively that another GM franchise would not.

Do you feel any vibration in the steering wheel when your CTS makes these noises? Has the transfer case been serviced? What about the front differential? At 139k, these items are past due. While this issue you are describing could be the transfer case, there are some things that could easily be checked to narrow down the source of the noise.
1. Driveshaft.

• Check the entire shaft for play or sloppiness.
• Inspect the driveshaft retaining bolts. Are any missing? They have been known to shear, causing the retaining clips to swing around and strike other parts of the vehicle.
• Inspect the driveshaft bushings. Over time, these can degrade and cause play as well.

2. Engine mounts.

• USE CAUTION HERE! Secure vehicle with wheel blocks, hood open. Have someone place the vehicle in drive with their foot on the brake. While holding the brake with your left foot, add throttle with your right foot while a second person watches for engine movement from a safe area. If the engine moves up and down in conjunction with the throttle, the engine mounts probably are in need of replacement. This could be causing the engine to come into contact with another part of the car.

These are a few items I would scrutinize before moving ahead with any more repairs.

 

[tinman]

Non-AWD driver here. One possibility could be your new tires. If you got some "sticky" tires (you mentioned new tires recently) those tires may "crab walk" when you have the steering wheel turned hard. While it is "not normal" in the real world it is normal for these cars. As I mentioned, this is one possibility. The AWD folks will definitely chime in.

 

[Juggernaught]

When I bought my CTS4 coupe a couple of months ago, I noticed some of this behavior when I made sharp right or left turns in a parking lot or pulling the car into the garage. I ordered some GM limited slip additive and added it to the rear diff. It cleared the up the symptoms about 80% and it's much less noticeable. The previous owner had the rear diff and TC serviced, and I wondered if enough limited slip additive was added during the service. Some scrubbing is normal in these cars due to the nature of the 4 wheel drive system.

There is also an old thread here where someone stated that the anti-slip additive needs to be replenished every so often because it "wears out". Don't know if that's true.

 

[Joseph Upson]

Welcome, Susan_C-- sorry to hear of your recent troubles.

If you expressed originally that the noise you were hearing was coming from the front of the vehicle, I'm not certain why a rear differential service was performed. I'm equally uncertain of what tools a Cadillac dealer would have exclusively that another GM franchise would not.

You know why they did a rear differential service, it was safe to do and get paid for. I don't believe the bit about the tools either, considering this was an diagnostic/inspection. If you don't have the tools, you send the customer to someone who does.

Interesting they knew not to tamper with the forward unit, or perhaps they didn't see it.

 

[jammgm]

I had a similar problem of what I would call shuddering in the front wheels when making hard turns left or right.
I changed the front and rear diff fluids and used mobil 1 w/slip differential additive and also changed the transfer case with fluid from the dealer on the recommendation of Long, Tinman, and others.
The car has been fine ever since. I changed it around 60k where the maintenance schedule is around 50k.
Sounds like it may be your cause and is way over due.

 

[Long]

You know why they did a rear differential service, it was safe to do and get paid for. I don't believe the bit about the tools either, considering this was an diagnostic/inspection. If you don't have the tools, you send the customer to someone who does.

Interesting they knew not to tamper with the forward unit, or perhaps they didn't see it.

The rear differential is the easiest of the three (F&R diff, TC) to change. Coincidence? I think not.
Was it due for service? Yes. Did it have anything to do with the customers concern? Likely not.
It's discouraging that this method of practice occurs at all, let alone at a GM establishment.

 

[Joseph Upson]

The front diff isn't difficult to access for a shop, the drain plug is right next to the oil pan and the filler not much more of a challenge than the rear for a shop with the vehicle in the air. The idea of them servicing the rear differential tells me they suspected a problem with the front diff and were not experienced enough to deal with it and didn't want to touch it.

 

[Susan_C]

Thanks for all the posts!
I have maintenance done on the car when I purchased it in October 2018. They changed all the fluids, rear differential, transfer case, etc.

Welcome, Susan_C-- sorry to hear of your recent troubles.

If you expressed originally that the noise you were hearing was coming from the front of the vehicle, I'm not certain why a rear differential service was performed. I'm equally uncertain of what tools a Cadillac dealer would have exclusively that another GM franchise would not.

Do you feel any vibration in the steering wheel when your CTS makes these noises? Has the transfer case been serviced? What about the front differential? At 139k, these items are past due. While this issue you are describing could be the transfer case, there are some things that could easily be checked to narrow down the source of the noise.
1. Driveshaft.

• Check the entire shaft for play or sloppiness.
• Inspect the driveshaft retaining bolts. Are any missing? They have been known to shear, causing the retaining clips to swing around and strike other parts of the vehicle.
• Inspect the driveshaft bushings. Over time, these can degrade and cause play as well.

2. Engine mounts.

• USE CAUTION HERE! Secure vehicle with wheel blocks, hood open. Have someone place the vehicle in drive with their foot on the brake. While holding the brake with your left foot, add throttle with your right foot while a second person watches for engine movement from a safe area. If the engine moves up and down in conjunction with the throttle, the engine mounts probably are in need of replacement. This could be causing the engine to come into contact with another part of the car.

These are a few items I would scrutinize before moving ahead with any more repairs.

Thanks! The dealer said there was a service bulletin on what he thought the problem was, and gave me a copy of it. The Service Bulletin said to change the rear differential. I guess I can't really tell where the sound it coming from. The Service Rep said he had never heard a sound like my car makes when the wheel is turned, and he was afraid to turn the wheel when he took it to the back to the mechanic.

It is a thumping/loud/grinding sound and the steering wheel jerks right and left when it happens. I believe you can also see the wheel jerking. But only at slow speeds. It is perfectly fine when driving down streets and making turns.

 

[Joseph Upson]

Thanks for all the posts!
I have maintenance done on the car when I purchased it in October 2018. They changed all the fluids, rear differential, transfer case, etc.

Thanks! The dealer said there was a service bulletin on what he thought the problem was, and gave me a copy of it. The Service Bulletin said to change the rear differential. I guess I can't really tell where the sound it coming from. The Service Rep said he had never heard a sound like my car makes when the wheel is turned, and he was afraid to turn the wheel when he took it to the back to the mechanic.

It is a thumping/loud/grinding sound and the steering wheel jerks right and left when it happens. I believe you can also see the wheel jerking. But only at slow speeds. It is perfectly fine when driving down streets and making turns.

That additional information is a game changer. That's not the characteristic complaint often made here with differential feedback. The service rep's opinion of it suggests they shouldn't have touched it except to address the problem, as it's clear they knew it wasn't normal. I believe the Cadillac dealer maybe correct that something is broken, but then again the description you've given sounds a lot like a fussy limited slip unit grabbing, which is made more prominent when the steering wheel is turned causing the front wheels to rotate at different speeds. That's probably why there's no problem when you're driving straight ahead.

The fluid at a minimum should be changed in the front differential and drained into a container that will allow it to be examined for metal contaminants. If there are none, perhaps a fresh refill will fix it. Be sure to ask for proof of any other diagnosis. If the transfer case is condemned, ask why. The first tech may not have even driven the car before and after and just serviced the differential. Your symptom description makes it pretty clear the problem is up front.

 

[Susan_C]

Thank you

 

[Long]

An OP just had a discovery in another thread which makes me wonder if it applies here. Just trying to rule out the obvious.

• Were all four of your tires replaced?
• Are all four tires the same size?

 

[Susan_C]

An OP just had a discovery in another thread which makes me wonder if it applies here. Just trying to rule out the obvious.

• Were all four of your tires replaced?
• Are all four tires the same size?

Yes, all 4 tires were replaced and they are the same size.

 

[Long]

OK, good to hear that can be ruled out as a potential cause.
Many times information like that can be unintentionally left out and has a huge impact on the troubleshooting process.

 

[Susan_C]

Thank you!

 

[andersonj006]

Check control arm bolt torques, especially lower control arms.

 

[FTSS]

I would normally just lurk and follow along. But since wind up and release due to ackermann angle (always more pronounced in reverse and at real slow speeds when the tires can't scrub as easily) has not been mentioned even once, I just wondered if that's no longer 'a thing' with newer designs.

And it might just be me, but I always default to any recent prior work as potential cause/ contributor to a new malady. In this case it might be relevant if this condition began either before, or after, the new tires "a couple of months ago".

 

[FMC]

I have a 2012 CTS that was making "popping"/"grinding" noises on slow turns when applying brakes lightly just after brake service at about 63k miles. Thought it was a problem with the work the shop did. Took it back and at first they thought it was "something inside the tire" because the took off the wheel, bounced the tire and "heard a metallic sound" when the tire/wheel was bounced. Off to the tire shop, tire dismounted, inspected, only some rubber pellets/debris inside. Back to the shop for more poking around. They finally figured out that the right front wheel bearing was worn out. oops. Beginning to hear same noise on the other side now.... ugh.
just my 2cents though.