Anybody changed their rear diff. fluid yet? Just wondering what weight gear oil to use and how much it holds. Ive been using Royal Purple motor oil with great results and was looking at them for rear end fluid as well. All opinions welcomed!

 

i use royal purple 85w140 in mine and im running 4.10 gears hope this helps

 

I used Mobil 1 75-90 and a tube of autozone friction modifier.

 

GoodQuestion..... i just had a hole new rear be cause i was haveing problems with it and the drive shaft and i put in 3.37's...... from the stock 3.55...but i put the Ford stock stuff...... but i guess it dont matter what you have in their as long as you keep it fresh...... and i tell you the 3.73's are made it alot more fun off the line.... and the gas meter show's it !

 

Red Line 75W 90 for the last 10k kms. It's a premium synthetic. Already contains the friction modifier for limited slip diff's.

 

Royal Purple 75W90

 

Amsoil 75w-90

 

SVT owners manual supplement tells exactly how much it holds.

 

All the major synthetics do not require a friction modifier.Though I here a lot of people still putting it in.( creatures of habit, I guess)

 

I forgot to put that in my last post I did add a bottle of Ford friction modifier when the Royal Purple 75W90 went in.

 

Thanks for the help!! Looks like Ill use the Royal Purple 75W90!

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