Gear Oil Weight Thoughts

[drew43a]

I just got my new Differential from Dr Diff and he recommends 85 140 weight  gear oil. the 140 seems high to me. Isn't 85 and 140 the winter summer weight numbers? Could you not go summer lower weight depending on where you live?  I have even heard some people use transmission fluid.  any thoughts on all this?

[Chryco Psycho]

I have always used 80-90w non synthetic

[docmel]

I get what you are saying, but its new, Dr Dif, they made it, etc.......................I'd go with what Dr Dif recommends  ANd I would never use Auto tranny fluid in a rear end

[anlauto]

I have always used 80-90w non synthetic

Yup....I just bought some yesterday for the 71 Cuda I'm doing right now. I buy sure grip additive also from my local Chrysler dealership too.

[headejm]

I just got my new Differential from Dr Diff and he recommends 85 140 weight  gear oil. the 140 seems high to me. Isn't 85 and 140 the winter summer weight numbers? Could you not go summer lower weight depending on where you live?  I have even heard some people use transmission fluid.  any thoughts on all this?

You just spent a good chunk of change with Dr. Diff so I would follow their recommendation. You bought from them for a reason - they know what they are doing. 

[dodj]

You just spent a good chunk of change with Dr. Diff so I would follow their recommendation. You bought from them for a reason - they know what they are doing. 

I would follow the doctors orders...

The numbers are the cold and hot viscous numbers. They do not have any relationship to motor oil numbers. 

[nsmall]

I have always used 80-90w non synthetic

That's what I was recommended by doctor diff along with the Ford additive versus the Mopar.  He has on his website exactly what to buy.