So the Assembly is not made anymore, so here I am with leaking differentials, and the mechanic telling me I need an entire new assembly and case, as its making the axels leak obviously slinging oil everywhere. The problem is this, GM doesn't make most of these parts anymore, so I am looking at some place that builds one and wants like 3000 and thats just the assembly, so looking at almost 6000 for everything, this sounds crazy. But other places I have checked with say they don't even know where to get parts, so they can't even quote me a price. Most places do not want to put on used parts, so I am asking for suggestions, or has anyone been in this predicament, shes fine everywhere else, and truthfully could probably get 5 more years out of her if this is fixed. But 6000 sounds crazy to me. Help!!

 

There are only 4 places the front differential can leak from and they are all seals that can be replaced and are available through multiple parts sources online as well as brick and mortar local parts stores.
Pinion seal, L&R CV(shaft) seals, diff cover seal - that's it unless you have a cracked differential case. If the case is cracked and leaking (which is not a common issue) I have a buddy who has several used cases and I can hook you up with him.
Your "mechanic" either is fleecing you for $ or is an idiot!

1. Locate the leak yourself.
2. Find a differential shop.

 

Welcome to HF.

MOVED. Tech questions belong in the vehicle specific sections ONLY.

The most common cause of Diff Leaks is OVERFILLING. Park it on a level surface and check the level. Look it up if you do not know how.

If you had your "mechanic" service the diffs before this started, I would absolutely check the fluid level myself.

 

Thought about this overnight. A plugged breather nipple, hose or the breather end itself can cause pressure inside the diff and force diff lube out of the seals.
Pull the hose off and stick something down the nipple to clear it, blow through the hose and see if there is an obstruction there also.

 

That is a good one, heat builds pressure if it can't breath.

Hopefully all that thinking did not do any damage.