I was wondering if anyone could verify a few things for me. I have a bad leak coming from the rear diff. on my 2004 mach 1. In the picture, it looks like this is where it is leaking from. What is that? Would that be the pinion seal? Also, how hard is this to replace? Do you have to pull everything, or is there another way? Thanks for any help.

 

This is another shot.

 

Hmmm... I thought mine was the rear gasket and that it had just got splattered around but I replaced it only to find out it was the pinion seal. I have been told it's the exact same amount of work which means a couple hours tops, or like $140 parts/labor to have a shop do it.

 

And fluid/gasket costed me $80 to do it myself so your lookin at about the same.

 

That would be a pinion seal leak. You can do it without tearing the rear apart, but you should make sure that you don't mess up the crush washer by over torquing the pinion nut when you put it back on. A cheap way to do that is to mark the nut and the pinion with a scribe line so that you put the nut back exactly where it was before. Too much torque and you can damage the pinon bearing, too little torque and you might leave some room for it to develop play.

 

Exactly what JD said.

I over torqued mine on another car a few years ago and messed up the crush washer. Just make sure whoever does it is good at doing gears, rears, etc.