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8 3/4” differential fluid?

Huicho417

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What fluid does everyone recommend for a 8 3/4 differential? I have been restoring my Coronet for a long time and the only items left to work on are the spring leaf bushings and changing out the differential fluid.
 
Does it have a sure grip? If so, clutch or cone?
 
No sure grip. If I jack up the car one wheel will spin in one direction and the other the opposite direction. Also, how much fluid should it take? Thanks
 
Then I’d use what was posted.
 
I used Lucas Oil 80w90
and a bottle of Mopar additive I bought from the Dodge Dealer here in town
(oops after posting I noticed you have an open Differential. You do not need the additive)

The 8.75 holds 2.2 quarts so you will need a small amount from a 3rd bottle

01_80W-90GearOil_Group.jpg
 
I used Lucas Oil 80w90
and a bottle of Mopar additive I bought from the Dodge Dealer here in town
(oops after posting I noticed you have an open Differential. You do not need the additive)


The 8.75 holds 2.2 quarts so you will need a small amount from a 3rd bottle

View attachment 1125415
It'll live just fine with the 2.0 quarts though. Been doing it like that since these things were fairly new....
 
No synthetic!

I agree
but to clarify the Lucas Oil 80w-90 is conventional with Lucas oil additives
The synthetic that Lucas Oil offers is 75w-90 or 75w-140 and clearly says synthetic on the bottle
 
I agree
but to clarify the Lucas Oil 80w-90 is conventional with Lucas oil additives
The synthetic that Lucas Oil offers is 75w-90 or 75w-140 and clearly says synthetic on the bottle
Thanks for the agree. I wasnt necessarily referring to your post, and i did notice the Lucas you suggested was not synthetic.
My post was just generic "dont use synthetic ".
I had a good friend, now passed, who ran a one-man rearend shop, specializing in race nine inch fords. If the customer insisted on synthetic lube, he would warrantee his work for six inches/six seconds, which ever came first.
He used nothing but Torco dino oil.
 
Tucson Differential says no on synthetic. They recommend valvoline and Orielly got it for me in two hours.

20201114_084940.jpg
 
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