Cadillac CTS 4 Rear Differential Noise

[pajeff02]

So I drove the car for around 40 miles today. The "growl" starts right about 25 mph and you can hear it until the car gets up to around 50 mph or so and then it is kind of drowned out. It is definitely in the driveline as the noise stays the same both on and off the throttle -- engine rpm alone does not alter the noise. If I let off and coast there is no change in the noise, however, it does go up and down with the speed of the vehicle. Shifting into neutral at speed made no difference. Applying cornering pressure to the steering wheel while at speed also has no impact and road surface has no impact. I am thinking maybe the carrier bearing on the drive shaft now.

[Cutlass]

I've replaced a few driveshafts for noise concerns. It's not super common but it does happen.
I've also had rear wheel bearings that aren't very sensitive to the classic side to side wheel bearing swerve test.

[pajeff02]

Were you able to determine which bearing by running it on a lift?

[Cutlass]

Yes. Listened to them at 25-30mph.

[pajeff02]

I tried hard this afternoon to discern the location on our ride up to the in-laws', but just cannot say for certain. Back on the lift she goes...

[Cutlass]

Now you know my daily struggle. Hard to make money when I waste time trying to figure weird noises.

[pajeff02]

I'll take a good old electrical issue any day of the week over a noise issue.

[pajeff02]

Car went up on the lift this evening and I had my brother run it up to around 25 mph. With all four wheels spinning, I went from wheel to wheel and could not hear anything. I then used the automotive stethoscope and carefully checked each wheel hub and the rear differential. I could not hear a growl emanating from any of the wheels and the differential was silent. Standing under the carrier bearing, which I can not access with the stethoscope due to the heat shield, I couldn't hear anything over the noise of the engine.

We then went for a drive and took turns riding in the back seat. The noise definitely seems to emanate from the rear of the car and we both though that it was loudest in the center. Placing my ear against the center of the seat cushion seemed to be where the noise was loudest. Sitting in the center we both thought that we could feel a slight amount of vibration too. I may drill a hole in the heat shield in order to access the carrier bearing with the stethoscope. Even with Stabiltrack off, we managed to totally piss off the computer and had messages on the display for ABS inoperative, Traction Control, it disabled the four wheel drive, and a failed brake booster.

[Cutlass]

There might be a little flap in the heat shield that you can flip over to access the d/shaft center bearing.
Also, there is a recall on those rear d/shafts on certain years of those CTS. Maybe you can get it replaced for free under the recall if it applies to your year CTS.

[pajeff02]

I popped the retainer pins for the back of the heat shield and managed to get on the carrier bearing with the stethoscope. In drive, with the traction control turned off, no apparent noise at the carrier bearing. I will need an assistant in the garage to run up the r's and will try it again later this afternoon.

Thanks again for all your assistance with this, Aaron. This one has me puzzled.

[pajeff02]

At speed, the carrier bearing is completely silent. Going to repeat the test again in a bit just to be sure.

[pajeff02]

Well... it turned out to be the front right wheel bearing. Swapped it out last night and the noise is now gone. Running on the lift, you could hear the faintest of noise from it with the stethoscope. I had my brother listen to everything without telling him what I heard and he came up with the same finding. Around $130 for the part and just over an hour to change it. The steering knuckle is bare aluminum and the bearing is bare steel - not a good combination. I had to beat the hell out of it with a cold chisel and my largest hammer to get it to break free.

[Cutlass]

And you swore it was in the rear!
I've been down that tricky road before. Glad you got it fixed.

[pajeff02]

Yep, I would have bet $$ on it being somewhere in the back half of the car. Thanks again for all your assistance!

[Cutlass]

If you ever have to do a rear wheel bearing on your CTS, they really get stuck in there too. I usually pull off the whole rear knuckle and use the press to get them out.

[pajeff02]

Thanks for the tip. Wheel bearings can be fun to play with. I had a pretty good fight with a Dodge Dakota wheel bearing earlier this year and before that I found out in person just how stupid the wheel bearing setup is on an '04 VW.