Time to address the diff leak. I plan on having the job done at a local Corvette shop but before I do I have a couple questions. Is there any upgrade/improved gasket or side cover I should be aware of and make sure the shop I am bringing it to uses it? Is there any method of repair that is better than another? Finally, it appears it is just leaking from the left side. Should both sides be repaired? Thanks in advance.

 

When I bought my 04 in 2014, had a leaky left butt. Only changed the seal in the left. So far, 7 years later, the right has not leaked. I go by the thought, if it ain't broken, don't fix it. But your choice.

 

The divers side is the most common to leak.
There is a bulletin on using a special red sealant for the case cover, its for Anaerobic curing.
There was a axle seal upgrade as well, you most likely will get this new style when you buy a new seal.
When I did this last year, I left the passenger side alone as it had no signs of any leaks.

 

 

I'm getting ready to do this over the next few days. I have everything out from under the car now to replace the rear main seal.
I'm replacing both seals because it's really easy to do with it out from under the car and my car has 205k miles on it. I also have only the driver's side leaking.
There is a new improved seal if your using original AC Delco parts. You can get a pair online from a couple of places for $25 bucks. I think the new seals are what you get almost by default. If I remember I'll post the part number when I get home.
Lots of good YouTube videos if you want to consider doing it yourself and saving a few bucks. Not really that bad with the diff in place either.
Good luck!!

 

Taking a little different approach, just something to consider.

I had a persistent diff leak after replacing all the seals when the diff was out of the car (didn't do the anaerobic seal method mentioned above). Even replaced one of the axle seals a 2nd time with no change.

Then I came across posts on this forum about a stuck differential vent valve, like this one: https://www.corvetteforum.com/forums...d-removal.html

Think about it, if the diff's check valve breather vent is stuck, then pressure is allowed to build up in the diff. The axle seals are the weak link with regards to withstanding pressure, so that's where a leak is most likely to occur.

What I did was replace the valve with a breather line, but that still allowed fumes in my garage when the fluid was hot.
I wound up And took just the spring, diaphragm, and top cap by removing them from the new valve and placing them onto my diff.
So far so good! (no leaks that I can discern, no diff fluid odor)

For reference, the diff was leaking slightly when I bought my Z06 with 56k miles. I finally swapped the valve parts @ 74k miles.

EDIT: Well the diff started leaking again after replacing the valve components. Guess I need to go back to the breather hose and deal with the temporary fumes in my garage.