Cadillac CTS 4 Rear Differential Noise

**pajeff02** · 12-28-2015, 04:15 AM

At just about 62,000 miles, my daily driven CTS 4 has developed a growling type noise. The noise started last week and is essentially constant. Unlike wheel bearing or tire noise, cornering and road surface had no impact on the sound so I suspected it was something more serious. I put her up in the air this afternoon and after checking each wheel for bearing play started spinning the wheels by hand.

I immediately noticed a "clacking" noise emanating from the rear differential. It almost sounds like a playing card on bicycle spokes is how I can best describe it. I checked and the differential fluid level is fine. This is the 3.23 open rear (non-posi) and I shot two vids this morning.

First video is with the transmission in neutral and the drive shaft spinning:

Second vid is with the transmission in park and the drive shaft stationary:

And a pic of the P/N:

Thoughts?

**Cutlass** · 12-28-2015, 05:50 AM

That noise sounds familiar but I can't recall what it is.

**Cutlass** · 12-28-2015, 06:04 AM

It's normal. I've checked another CTS here and it does it too. Not sure what it is, but don't worry about it.

**pajeff02** · 12-28-2015, 09:42 AM

No kidding. It sounds for sure like something is fragged in the rear.

**pajeff02** · 12-28-2015, 02:25 PM

That is just so weird... I don't doubt you Aaron, but would love to know what is making that noise. It's an open rear, so no clutches, springs or anything of that nature in there. I also have the "growl" that developed within the last week to still contend with then. Ugh.

**Cutlass** · 12-28-2015, 02:47 PM

I'll check out a few more CTS's as they come in for work. The one I checked today was the only one that came in today.
What part of the car is the noise coming from? Front, rear, middle, left, right?

**pajeff02** · 12-28-2015, 05:33 PM

When driving, it is definitely emanating from the rear somewhere. Road surface makes no difference. Cornering makes no difference.

When I spin the rear wheels by hand, not only can I hear the noise that is depicted in the vids, but I can also feel it in the wheels. I dropped the fluid this evening and although the magnetic drain plug had some sludge on it, I would not deem it too excessive. I could not see any metallic particles suspended in the gear oil as I washed it back and forth in a clean, light colored, drain pan. I shoved my bore scope in the fill hole and can view the ring gear which appears fine. Waiting for the rest of the fluid to drip out so I can investigate a bit more tomorrow night.

**pajeff02** · 12-29-2015, 03:31 AM

**35th-ANV-SS** · 12-29-2015, 05:15 AM

Maybe the CTS that came in has the same problem. That sound doesn't sound normal to me, especially if the sound wasn't there before.

**pajeff02** · 12-29-2015, 07:21 AM

I was trying to remember if I ever spun the wheels with the car in the air before. I generally do roll the wheels around to look at the tires when I service a car, but I cannot specifically recall ever doing it before on the Caddie.

***SMWS6TA*** · 12-29-2015, 07:54 AM

Jeff did you take the drive shaft off and check the pinon?

It sounded like mine was doing in the Durango back last spring. It mimic what you described. Once the drive shaft was off it was very easy to tell the pinon bearings were toast.

**Cutlass** · 12-29-2015, 09:01 AM

The fuzzy stuff on the drain plug magnet is normal. I'll make sure to check a few more CTS's out

**Cutlass** · 12-29-2015, 09:40 AM

Found another CTS that makes the exact same noise. I think it's a normal characteristic.

**pajeff02** · 12-29-2015, 12:36 PM

Ok - I think I found an explanation. The rear differential spider gear assembly has a bit of pre-load on the beveled gears and that is why a regular "clacking" can be heard when a wheel is spun with the car on the lift. While spinning the wheel (with the transmission in park) only the spider gear assembly spins inside the differential as it transmits the rotational force to the far wheel (which spins in the opposite direction). The carrier bearings and pinion bearing remain stationary and cannot be the source of the noise.

Granted, this does not explain the "growl" that the car seemed to develop within the past week, but it does offer a plausible explanation for this noise.

Aaron -- thank you again for looking into this!

***SMWS6TA*** · 12-29-2015, 12:42 PM

Interesting...

**Cutlass** · 12-29-2015, 03:24 PM

Here is what I would try. Put the car up on the hoist, engine running, transmission in drive. Have a helper run the throttle up to whatever MPH you think you might hear the noise. Maybe 25-45 mph? Then you get under there and try to locate the noise. Use a long pry bar or screwdriver as a listening device. Listen to both rear wheel bearings, the d/shaft center support bearing, differential, and the transmission/transfer case areas.

**Cutlass** · 12-29-2015, 03:31 PM

If no one is around to help, put the Trans in second gear and stick a prybar between the seat and gas pedal. Use the power seat to adjust the RPM/MPH

**pajeff02** · 12-29-2015, 05:48 PM

Actually did that tonight, but only at idle with the transmission in drive and traction control turned off. I used a mechanic's stethoscope on the transmission, transfer case, rear differential and wheel bearings. I will probably repeat this test as you suggested at a higher speed when I have some help in the garage. Going to drive the car tomorrow and see what I hear.

**Zapper2003** · 12-29-2015, 05:52 PM

I'm only a phone call away

**pajeff02** · 12-30-2015, 03:38 AM

If it keeps acting up your phone may ring. Even Dawn says she noticed that it was noisy the last few times we had it out. I may just have to try the "turn up the radio and ignore it" method for awhile until something definitive pops up. Last night, I did finally look up above the tunnel heat shield and there is a carrier bearing on the drive shaft, so that is one more possibility.