Cadillac CTS differential / transfer case noise

[Nassif]

Hi guy,

I would like share that I buyed a used 2008 CTS in Nov 2015 with 95K kms on meter. Several week after I found a vibration and felt it like a problem somewhere in the suspension. I was not sure it about it, but the same happen with my old car Escalade 2007. Well I took it the same garage that I used to take my car. They told me that there is some problem in the front differential/transfer case so they replace that first. But after replacing it the problem was still there. When I took my vehicle and came back it has the same noise. I took back my car to dealer and inform him about the same, but now this time they said another story which says output shaft coming from the transmission and the input shaft to the transfer case had been stripped. Well it was hardly understandable to me. 
I smell something that lead me to think that they are unnecessary trying to get whole lot of money in replacing the part from my pocket, I bring my vehicle back honestly don’t want to pay for lazy and unwanted repair anymore. 

What you guy think, Should I place ad for selling the car and buy new one this time? 

Or is there any quick solution that I can give to the dealer to repair my car without a hassle and in small amount? 

 

[gautam]

Hi Nassif,

I am sorry to say the problem you describe is a known problem on your car. You mention that your Escalade had the same problem, but this is because the driveline components on the Escalade are the same as those on your CTS.

Yuu don't mention if the problem is worst in second gear, but this is usually the case. Nonetheless, the problem is caused by tires that are not exactly the same size, or tyres and wheels that are not exactly alingned. Any difference in tire diameters or rolling resitance causes the transfer case on AWD systems to partially engage, which causes a rumbling, whining, or sometimes a whistling noise in second gear, but it could occur in other gears as well, and sometimes in all gears depending on how engaged the transfer case is. In some cases, the noise is accompanied by a vibration, which is the result of the drive line being only partially engaged.

The thing to do is to check your tyres for any sign of uneven wear, but also check that all the tyres are exactly the same diameter. If for instance only the front or rear tyres were recently replaced, it is possible that there is a size difference between the tyres on the front and rear axles.

This will cause noise you describe, because the wheels are rotating at diferent speeds, which causes the transfer case to partialy engage. Replacing all four tyres at the same time is often the only way to fix this problem, but do not replace any more mechanical components before you are sure the tyres are all the same size, type, tread pattern, and inflated to exatly the same pressure.

Infation differences effectively change a tyre's rolling resistance and and circumference, which can also cause this issue. However, if the tyres are exactly the same and the noise/vibration is still present, it is possible that the tranfer case has suffered some mechanical damage already, and the only way to fix this is to replace it.

I hope this helps, and please keep us posted since other members may have the same problem.