Changing my gear oil but.........

[90Notch]

Ok, so I'm thinking about changing the gear oil in my Mustang (4.6L w/traction loc). The owners manual recommends 80w90 and I was thinking about switching it out for some Royal Purple Max-Gear. The only problem I have is that RP only carries quart sizes for the 75w90 weight or 75w140 weight, the 80w90 weight comes in 5 -gallon pails and I only need 2 quarts.

So is it safe to use the 75w90 or 75W140? I know this stuff already has the friction modifier for traction-loc. Thanks in advance!

 

[tom slick]

75w-90 is a fine replacement for 80w-90

 

[D-Roc]

I would go with Chevron ESI 80W90 if I were you...specs looks great on this oil, and if I didn't have sub freezing zero temps often that is what I would use. Supposed to be superior protection in a regular 80W90 grade.
Other than that, I like Amsoil Severe Gear and Royal Purple...Using Pennzoil 75W90 right now because I got a 5 gallon pail for free....

 

[Jim Allen]

I agree... the 75W90 would be perfectly fine, or the 75W140. I'm not seeing 80W90 any more on any of the Ford recommendations. To my knowledge, they have gone to recommending synthetic 75W90, or 75W140 in trucks. The axles haven't changed.

 

[artificialist]

I have worked on many Crown Vics that take synthetic 75w140.

 

[PT1]

Stick with an 80w90. I have had diffs whine when converted to 75w. Don't ask me why but it has happened.