Which Diff oil..??
Thread Starter
Cruising
Joined: Aug 2011
Posts: 12
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Which Diff oil..??
What diff oil should I be using in my '72...I assume it should be LSD oil with the GM additive but I'm confused by the various grades. I should state that I just bought the car it runs fine but the oil looks like it was a long while ago that it was changed.?
Le Mans Master
Joined: Sep 2004
Posts: 5,116
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From: Livonia MI
Which ever gear lube you decide on, wouldn't be in any hurry with the additive, as may not need any. The additive allows more posi slip around turns to quiet things down, but sometimes to much, not making the rear feel like posi anymore. Lot easier adding this this suff later, than trying to take it back out. Been there a few times, and know a few things.
Burning Brakes
Joined: Oct 2001
Posts: 1,241
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From: Okinawa Okinawa
I used mobile one w/ additive but any of the major brands will not let you down. Everyone has their favorites. Just do an advanced search for diff fluid and read through some of the posts and make up your own mind. If you don't believe me, look at the motor oil sticky and you will see 1,000 opinions and everyone thinks they are right.
CF Community Team
Joined: Oct 2004
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From: Cape Cod, Mass.
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80/90 weight gear oil with one 4 oz bottle of GM posi lube. I've been using that in all my old Corvettes for 42 years and have never had a rear end issue. That's what they were designed to use. Put the posi lube in first, fill it with the 80/90 and then do some figure eights to work it into the clutches.
Burning Brakes
Joined: Sep 2005
Posts: 1,050
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From: Lewes Delaware
80/90 weight gear oil with one 4 oz bottle of GM posi lube. I've been using that in all my old Corvettes for 42 years and have never had a rear end issue. That's what they were designed to use. Put the posi lube in first, fill it with the 80/90 and then do some figure eights to work it into the clutches.
Did the above in my 73 a few months ago and it eliminated the clicking sounds during right turns. Plus the oil that came out verified it needed changing.
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Le Mans Master
Joined: Sep 2004
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From: Livonia MI
As mentioned before, don't put the friction modifier in, just because other guys automatically do it, because they think it's the right thing to do. I have a C6 ZO6, and the rear end chatters on cold day parking lot tight turns. Lot's of guys just dump in some additive, but not me. Can live with some noisy cold day tight turns knowing I've got got a tight rear diff clutch pack. These cars come from the factory with no diff additive, so just leave it alone. I've let other people borrow the car, and nobody really complains about it.
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Joined: Oct 2004
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From: Cape Cod, Mass.
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As mentioned before, don't put the friction modifier in, just because other guys automatically do it, because they think it's the right thing to do. I have a C6 ZO6, and the rear end chatters on cold day parking lot tight turns. Lot's of guys just dump in some additive, but not me. Can live with some noisy cold day tight turns knowing I've got got a tight rear diff clutch pack. These cars come from the factory with no diff additive, so just leave it alone. I've let other people borrow the car, and nobody really complains about it.
I also have a C6 Z06 that was making the noise from the rear end. I did a rear end fluid change to the newer fluid with the friction modifier in it. The noise stopped. This was designed for the newer Vettes. Still use the 80/90 with the GM posi lube in the old ones.
Melting Slicks
Joined: Nov 2001
Posts: 2,668
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From: Eastern US XX
I guess I'll have to respectfully disagree with you on all counts. The old cars DO need the friction modifier. The longer you hear noise from your rear end the more likely you are to cause damage to the clutches.
I also have a C6 Z06 that was making the noise from the rear end. I did a rear end fluid change to the newer fluid with the friction modifier in it. The noise stopped. This was designed for the newer Vettes. Still use the 80/90 with the GM posi lube in the old ones.
I also have a C6 Z06 that was making the noise from the rear end. I did a rear end fluid change to the newer fluid with the friction modifier in it. The noise stopped. This was designed for the newer Vettes. Still use the 80/90 with the GM posi lube in the old ones.
ABSOLUTELY put it in!
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