- May 28, 2015
- 1977 light blue
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.