Does GL5 Already Have Positrac Additive?
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
Not sure if it includes the friction modifier in it, but no way I'm ever putting that stuff in again. Tried it in a few cars, and basically took most of the posi clutch pack lock up away, making it feel more like an open diff, spinning only one tire. Ended up draining and flushing everything out. I'll put up with the noise around turns.
OK, by request, I edited the post as actually meant the GM friction modifier additive and not the GL5 fluid.
OK, by request, I edited the post as actually meant the GM friction modifier additive and not the GL5 fluid.
Last edited by Vette5.5; Aug 22, 2011 at 02:00 PM.
Melting Slicks
Joined: May 2009
Posts: 3,079
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2024 C3 of the Year Finalist - Unmodified
If you are not certain about what to put in your differential, why not just go to the local GM dealer and buy their lube and additive? Suck the old stuff out, fill it with the new, go find an empty parking lot and spend some time making left hand and right hand circles.
Melting Slicks
Joined: May 2009
Posts: 3,079
Likes: 315
2024 C3 of the Year Finalist - Unmodified
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Le Mans Master
Joined: Oct 2007
Posts: 7,455
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From: RI, Now Franklin/Nashville TN
I have been using Mobil 1 75W-90 GL-5 for over 20 years now in the diff-No chatter, no noise, perfect double patches if you spin the wheels, so a little perplexed by the comment above that GL-5 makes a limited slip diff act like an open differential. Anyone else experienced a GL-5 gear oil not working correctly in their corvette diff?
I have not used any additives in the diff with the GL-5 since 1992-works perfectly!
I have not used any additives in the diff with the GL-5 since 1992-works perfectly!
Last edited by jb78L-82; Aug 22, 2011 at 02:43 PM.
Melting Slicks
Joined: Nov 2001
Posts: 2,668
Likes: 43
From: Eastern US XX
Not sure if it includes the friction modifier in it, but no way I'm ever putting that stuff in again. Tried it in a few cars, and basically took most of the posi clutch pack lock up away, making it feel more like an open diff, spinning only one tire. Ended up draining and flushing everything out. I'll put up with the noise around turns.
I have also been using Mobil 1 75W-90 GL-5 - plus 1 bottle of the GM Posi additive - for many years without and issues - posi works perfectly.
Last edited by pws69; Aug 22, 2011 at 12:25 PM.
Le Mans Master
Joined: Jan 2006
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From: Butler Pa
