[Smith]

I have lost fluid out of the breather at the top of the differential on two different occasions on the track. The first time Ford said it was overfilled at the factory; to correct they lowered the fluid level.

No problem on the track until I change out the ring and pinion. Differential probably got filled to the bottom of the fill hole, as noted in the Maintenance Specifications. Next trip to TMS and I came back with a pint of 75W-140 on the undercarriage and rear breaks, which cause another set of problems.

The rear axel is picking up a lot of heat for the rear end, axles, breaks and exhaust. Anyone else having this kind of a problem?

[madmaxx69]

The rear axle gets very hot on all cars/trucks the ring and pinion running together causes a lot of heat, thats why the heavy oil 75/140.

As far has losing gear oil seems odd because when filled to the bottom of the check hole is correct.

Just wondering why would you change the gear in a 2009 Mustang, you killed the drive train warranty....

[Smith]

Replaced with Ford Racing Performance Parts (3.73) by Dealer. The problem occurred once before the parts change and again after the parts change. In both cases this happened during the fourth 30 minute session on the track and the axel would have been exceedingly hot. Not sure how much heat I am picking up from the rear breaks.

I appreciate your input and look forward to your reply.

One correction on post; year model is 2008 not 2009, my typing error.

[Smith]

Why change ratio:

I drove a GT500KR which has the 3.73 and enjoyed the noticeable change from the 3.31 in the GT500. I don't need the higher top end on a road course.

[GT500Girl]

Hmmm...no...don't know of anyone that's had that problem.