Differential fluid change

[stevolwevol]

I am preparing to replace the differential fluid in my 79 (Eaton). I've read some say always use GM additive, and I've also read using NAPA etc is fine also. Is there a real difference? Is there such a thing as too much additive? My plan is Valvoline GL5, plus NAPA additive. Input would be helpful.

 

[Tom Bryant]

I've never used anything other than GM lubes. The part numbers have changed over the years but the product is what is recommended for a GM posi rear axle. If the other brands meet the same specifications they should be alright. I can't say from experience though.

GM AC Delco Axle Lubricant 89021669

GM AC Delco Fluid 88900330 Limited Slip Axle Lubricant Additive.

 

[stevolwevol]

I've never used anything other than GM lubes. The part numbers have changed over the years but the product is what is recommended for a GM posi rear axle. If the other brands meet the same specifications they should be alright. I can't say from experience though.

GM AC Delco Axle Lubricant 89021669

GM AC Delco Fluid 88900330 Limited Slip Axle Lubricant Additive.

Thank you Tom, I ended up taking the big leap and used the NAPA stuff. The differential and posi work fine. Thanks again.

 

[douglasamariani]

A

lways use GM additive ​