Diff cover leaking

jmc01gt

Member
Mar 11, 2010
60
4
9
Austin Texas
I just noticed some oil dripping on the floor recently, and when I looked after my car sitting for two days there was a huge puddle of oil under my diff. The bottom of the gas tank is covered along with the sway bar. The obvious fix is to just pop the cover, replace the gasket and RTV, then put it back on (or swap to a heavier cover). But before I do that I want to figure out why it started leaking.

I swapped out to 3.73's almost 5 years ago, no leaks prior to this. I recently upgraded the rear suspension...in January, but no leaks prior to this. I did take it to the track recently, but I have bolt-ons, run street tires that I don't deflate, and only ran a blistering (sarcasm) 14.3 @ 99. I've hit it hard from stoplights before this, and run it at the track prior to the suspension upgrades. So any ideas of why it started leaking now, or is it just one of those things that happens?
 
I know it is coming from the rear as I can see the slow drip from the bottom of the cover.

I had a Mustang specialty shop do the change back in 05 as the car was only driven when I was on leave from Alaska...so I don't know the specifics of what they put in the gear oil. The shop is still in business so I am assuming they do things right. I'll check the breather, but I am pretty sure everything is clear under there.