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Topic: Differential gear oil

in Forum: C3 Driveline Components


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Differential gear oil (1/5)
 12/11/20 9:36pm
BillHanna
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Cana, VA - USA

Vette(s):
1975 Stingray 71 350 engine Flat top pistons Sniper fuel injection Hyperspark ignition Vintage Air air conditioning Borgeson power steering box


Joined: 7/3/2016
Posts: 234

I had my mechanic check the diff oil today, and the level was fine, but he said that it was very thick, like 90+ weight gear oil.

We thought that a posi unit would have had a lighter oil in it.

Are we wrong?

 



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Re: Differential gear oil (2/5)
 12/11/20 10:03pm
manchestersharkLifetime Member
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Equinunk, PA - USA

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1972 conv, 4-speed, 350, 200hp, numbers match, rally wheels, war bonnett yellow w/white top. good condition, nice driver.


Joined: 10/31/2007
Posts: 2047

GM makes a small bottle of additive for all the older positraction rears. I used Pennzoil 70-80 gear oil and two bottles of additive. If in  tight circle or figure eights, the rear chatters or clunks, you need to drain it, put new oil and additive in. THEN drive in tight figure eights for a few minutes, going both directions, it should seat the clutches and quiet the movement.

Re: Differential gear oil (3/5)
 12/11/20 10:44pm
F4Gary
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Grapevine, TX - USA

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Joined: 8/26/2006
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I think some of the newer synthetic diff oil already has the additive in it.



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Re: Differential gear oil (4/5)
 12/11/20 11:21pm
BillHanna
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Cana, VA - USA

Vette(s):
1975 Stingray 71 350 engine Flat top pistons Sniper fuel injection Hyperspark ignition Vintage Air air conditioning Borgeson power steering box


Joined: 7/3/2016
Posts: 234

Well, there is no clicking noise, although after the last install of the engine I hear a whining noise somewhere in the drive-line.

I didn't know if I would be better just leaving it as is, or have the gear oil changed.  Sometimes changing things can create problems afterwards . . .

 



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Re: Differential gear oil (5/5)
 12/12/20 12:15am
73shark
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Overland Park, KS - USA

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1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 659

I don't remember for sure but I believe I put 80W in my differential plus the Positraction additive from GM.



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1973 L-82 4 spd

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