differential worn out?

I can't see a worn differential contributing to excessive tire wear. Maybe in severe conditions where the limited slip clutch plates were stuck and you were doing continuous tight figure eights.

There is a howling noise while I am driving only. Its most constant when I am doing about 45 MPH. The noise sound changes in loudness and HUMMING when I increase and decrease speed. I think it is coming from the rear differential. Am I right, and what would the repair cost if needed. Thanks michael

It's either a axle bearing or carrier bearg, or pinion, and has to be further diagnosed b4 the how much can be answered!

when i turn my car on i proceed to put it in drive gear it will not move unless i turn car off step on brake then put the key back in the ingntion turn car on then it moves into drive gear. what could that be
?

Are you stepping on the brake the first time around, I would assume you are, but it does not say so. There may be an issue with the shift lock solenoid, or the signal that it needs.

On my 2005 cts I have a whing in my differential I had it for awhile. My understanding cadillac had this problem for awhile. Is there anything that I can do to make the whing to go away besides replacing the differential? Thank you.

It depends on what is damaged-you just have to inspect it to determine if it needs replacemebt

check the trans filter it maybe clogged.

This is a CTS-V , 6 speed. Will not go into gear unless engine is shut off. What would approximate cost of repair be? Also what is approximate cost to repair rear differential which is "cracked" and makes a thumping noise upon acceleration.

sounds like a clutch is bad, you'll have to check locally although i'd say you are looking at close to $4000 for clutch and maybe a rear end housing. you might check and see if you can get the rear end used.

Noise from rear end. tires and hub bearings have been check. what type of charges to exspect with differential repair?

All depends on the severity of damage. It could get easily into 1000 to 2000 or more. Alldata doesn't show any labor times.