I am going to change the lubricant of the differential on my Electra -70. The Buick Chassis Service Manual is very specific on that a special type of gear lubricant is to be used if the differential is of the positive traction type. They even say to flush the system should just a small amount of regular lubricant be added. Is this information still valid with the lubricants of today? If so, how to know if I have a positive traction differential?
The differential should have a tag on one of the bolts if it's a posi. However that tag may have gotten lost over the years. If you jack up the rear, put it in neutral and turn one wheel, the other one should turn in the same direction if it's posi. Or you could just do a burnout and see if you leave one or two marks.
On a Posi you will put about 2 Quarts of 80-90 w oil along with a small bottle of friction additive. You fill the rear with the oil until it comes out the fill hole, but add the entire bottle of friction additive first.
Yes, but I believe it still uses the friction modifier. Very important! Hope “Monza” will respond. He would know best…
The big 9 3/8” rears had a clutch style unit,but still uses the same oil and additive as the cone units.
Brian has it dead on. Clutch eaton unit and like all LSD rear limited slip diff fluid needs to be added. A body Buick used the cone type Posi unit till 1970 (borg warner / Auburn )... then 8.5 came in with the traction lock square tab clutch AND YES there were still 8.5 cone units also ...I have rebuilt a few of those too. Chevy even had BORG WARNER cone units also... Everything was possible... lol. Jim JD Race
