Repair or replace? Yes I'm an idiot.
 

Drained the front diff while doing the oil change:eek: needless to say by the time I realized it was toast. My question is, should I repair my unit or source a used one?

Oh man sorRy to hear that..I'm sure it would be cheaper to repair than replace.. Good luck man!

Actually - usually with this sort of part, a good used is way cheaper then the bearings/gears/seals/etc needed to repair it - and that's not counting the labor for the job (I rather doubt the OP is skilled in matching gear-mesh.)

I assume there was one small point missing in the OP's post - he drained it - then DROVE it? - with no oil in the diff? How far was it driven and what are the symptoms? Tried refilling it with the correct oil? Might surprise you if the vehicle wasn't run down the highway 100 miles..

I'm going through the same thing with my 911 C4S. I looked at a new part, a rebuild job and at a used part. I ultimately settled on a rebuild. It wasn't cheap, but it was much less expensive than a new part. I liked this option because my front differential is now essentially new, and with a used part, you really don't know the history.

For my C4S, the rebuild was roughly $3,200, which includes parts and labor. I'm not sure how this compares to a Cayenne rebuild.

Yes, I drive about 15 miles or so and then noticed a whinning. Returned home figured out what I did. Added fluid, but whe whine is still present. Any one have a spare diff lying around??

If the whine is still present a bearing isn't happy. Might you find out which bearing? Mebbe - have you ever rebuilt a differential? Do you know about gear-mesh patterns? If not - I see your choice as:

1 - Used part. If it comes from a reputable wrecking yard they will guarantee it. This is the route I'd take. There are yards parting out Cayennes on Ebay on a fairly regular basis.. and since this isn't a high failure rate item, I'd bet it doesn't go for a huge sum.

2 - Find someone to rebuild it. Who? Dunno - the people who used to be able to do that sort of thing are rapidly dying off. New mechanics are trained to replace subassemblies. Rebuilding is too risky (since the dealership and mechanic would eat any errors, and the new parts come with a warranty including labor if done at a dealership) for most mechanics now. You need an old timer who has done a lot of this particular part. I'd bet that's almost impossile to find, at least in the US (mebbe you have someone in Detroit?)

mesh patterns and clearances aren't hard, more time consuming and hopefully you get it right the first time! :D

I think the biggest thing is having the right tools to finish the job. presses, cut off wheels, c-clip tools....giant hammer! lol

I think any competent 4x4 shop can rebuild very easily. And a lot of them will guarantee their work.

I am an idiot as well
 

What did you end up doing to fix your front differential, and how much did it cost?