Front/Rear Differential Fluids?

[busa2009]

im wanting to change my front and rear differential with amsoil and was wondering what is the spec on the fluids?
front 75W85 GL5
rear 75W90 GL5
Im hearing it goes by your gearing ratio Is there any service manuals on this in this site if so where

 

[jdefoe0424]

Yeah, weights are listed in the manual. Front is correct(80W90 is not going to make a darn bit of difference except slightly in MPG), rear could be 75W140 if you have the 3.92 gear ratio.
Mopar has a slip lock additive that may be required if you have the factory limited slip, you may or may not need it as some diff fluids already have the friction modifier to some extent. You can try without it first and if you notice that the LSD is grabby and chirping on dry pavement then you can add the slip lock.

You're already an AMSOIL customer?

 

[busa2009]

Yeah, weights are listed in the manual. Front is correct(75W90 is not going to make a darn bit of difference except slightly in MPG), rear could be 75W140 if you have the 3.92 gear ratio.
Mopar has a slip lock additive that may be required if you have the factory limited slip, you may or may not need it as some diff fluids already have the friction modifier to some extent. You can try without it first and if you notice that the LSD is grabby and chirping on dry pavement then you can add the slip lock.

You're already an AMSOIL customer?

No it will def be my first time using amsoil my uncle was telling me what he runs. So your saying I just need to make sure on my gearing and if I have 3.9 gears I need to go with 75w140


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[cskindt]

No it will def be my first time using amsoil my uncle was telling me what he runs. So your saying I just need to make sure on my gearing and if I have 3.9 gears I need to go with 75w140


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You don't need to, just if you tow often or heavy.

It seems people with 392s like to go to them truck pulls and hook up. In which case 140w would offer more protection than 90w, or you could compromise with 120w.

 

[busa2009]

this is what my rear looked like 2019 ram 1500 5.7etorque 116,000 miles

 

[FourByBud]

this is what my rear looked like 2019 ram 1500 5.7etorque 116,000 miles View attachment 151589

Looks delicious Any issues with rear end?

 

[busa2009]

Looks delicious Any issues with rear end?

nope nothing so far but what's weird they so don't change it unless you tow sure looked dirty to me and even may emulsified I will change again on next oil change to see what the fluids look like