The last few days I have been hearing some fairly loud whining from the rear end. I thought maybe it was my tires because I put my old stock wheels back on the rear temporarily while I am waiting for my new tires. This noise started about the same time. I noticed this morning that I heard a pop and then the noise went away. I think it was coming back after awhile. I will see again tonight.

I have never really looked at how power is transferred etc in the Audi, but could the slightly taller tires still being on the front be causing this, or do I have a problem?

Either way, I should have the new tires on Saturday and everything back to normal. I guess I will see if the noise goes away then. I do have to put another 150 miles on the car between now and then getting back and forth to work? Am I hurting anything with the slightly taller tires on the front (no more than 1/2" taller)

 

I'd be very hesitant to run different front and rear tires at any speeds over 40mph, and then only till you can get the problem resolved..

 

It appears something is toast in the Haldex/Rear Differential. I don't think it was related to the tires. The difference in the tire heights wouldn't be any more than if you had new stock tires on the front and bald ones on the rear.

Anyway, the rear end let go big time on the way home from work. It started making all kinds of bad noises and constant clunks. I suspect a gear inside is broken and maybe worse.

I can spin one wheel and the other one does not spin in the opposite direction (with the driveshaft locked,I.E in gear. I can also spin both tires in the same direction freely with an occasional hangup like a chunk is grabbing.

I knew the diff or a CV joint was toast. Unfortunatly the CV's are fine

I have the bently out now and looking up how to drop it out the easiest way.

I found two other problems while I was under there. The ground strap cable from the body to the Rear diff had broken off on one side (appears to be from years of vibration I guess).

Also the little link that goes from the "control arm" up to a sensor with a wiper arm on it, was broke. It appears the ball socket dried up and this cracked the plastic arm allowing the insert to pop out. I fixed this already with some cleaning and some fresh grease and since the nutsert just pulled out of the arm due to the crack I was able to make something work.

I think these problems explain why I would sometimes get a pop and what felt like a slip in the rear end every great now and then. My car also handled scary bad in the snow last year like it was going to go out of control any second.

Anyone doubt the diff is toast? If so I am sure the debris ground up everything. Think the Haldex is toast as well?

 

Can these rear ends be rubuilt, or are they toast when they go? I hate buying a used one with who knows how much life. The good news is that they don't apear to be too rare and aren't too expensive.

 

I got a used diff/haldex unit off a low mile wreck for $425 locally. I looks as if the previous owner servied it correctly. It has the plastic filter (black).