Differential fluid type 1975
Thread Starter
Cruising
Joined: Mar 2016
Posts: 13
Likes: 0
Differential fluid type 1975
i am unable to get to my manual due to storage and this is my first diff fluid change. what weight should i use? i already have my GM additive, should i stick with GM gear oil? or is any other brand non-snyth oil okay?
Racer
Joined: Jul 2013
Posts: 366
Likes: 19
Rear fluid
Hello. There has been much discussion on this topic. Many feel modern synthetic fluid is fine. Others say stick with the GM fluid. My 73 sat for MANY years. When I finally was able to drive it, had a clunking noise. Suctioned out the new fluid, with a turkey baster and tube, took a while, but worked. Put in GM fluid, and two 4 oz bottles of additive. Drove in figure 8's, or opposite circles, to exercise it, noise gone! Plenty to read on the topic on this forum, which is a great forum! Good Luck!
Le Mans Master
Joined: Aug 2006
Posts: 7,419
Likes: 1,554
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
SAE 80W or SAE 80W-90 GL-5.
To get the nut off use a 8 point 5/8 socket.
https://www.gmheritagecenter.com/gm-...tion-kits.html
To get the nut off use a 8 point 5/8 socket.
https://www.gmheritagecenter.com/gm-...tion-kits.html
Le Mans Master
Joined: Oct 2007
Posts: 7,444
Likes: 970
From: Tennessee/Rhode Island
I have used Mobil 1 75W-90 synthetic for 26 years now with no friction modifier and the diff is perfect...go synthetic...friction modifier or not
Last edited by jb78L-82; Apr 6, 2016 at 06:47 PM.
