The rear end in my cobra was starting howl on decel.

Pulled it out and have a ford racing rebuild kit, 2012/2013 finned aluminum rear diff cover with drain and fill holes, as well as royal purple synthetic lube on roder. I have a new set of ford racing 355's waiting as well.

I have been told synthetic is no good, to go with regular lube. Thoughts?

Have ford racing friction modifier to go in as well.

 

The new ones all use 75w140 synthetic and we very rarely see issues.

 

Stay with the tried tested true dino gear oil. I can show you a pic on what happened to my pinion bearing with having synthetic oil in my GT's diff due to the condensation that was created in the diff housing in having synthetic oil, the moisture pitted the collar on the pinion bearing during storage seasons.
My buddy, a Ford tech said he has had a few stangs come threw in the past few years with similar issues with stangs running synthetic oil in the diff that don't see a lot of road time.


But in the end, it's all a personal choice.

 

Thats what i figured, but have heard mixed reviews about it.

 

Thanks again. My friend is a class A gm mechanic, and said the same thing about synthetic, and to avoid it.
Thanks for the re-inforcement 1low

 

Parts barely made it in before christmas. Starting the tear down tomorrow night. Cant wait for a quiet rear end.

The ford aluminum diff cover looks amazing! Excited to get this thing back in the car. Getting tired of seeing the car on jack stands, lol.