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Rearend oil & limited slip additive? #954260 03/20/11 02:50 AM 03/20/11 02:50 AM
Joined: Jan 2003 Posts: 1,046 Colorado Springs T/A CARe OP super stock
T/A CARe OP super stock Joined: Jan 2003 Posts: 1,046 Colorado Springs	I'm putting a 4.56 limited slip chunk in my 8 3/4. Primary use will be street. What oil wt. should I use (and why)? Also, what's a good limited slip additive? Is the additive Auto Zone sells any good?

Re: Rearend oil & limited slip additive? [Re: T/A CARe] #954261 03/20/11 07:03 AM 03/20/11 07:03 AM
Joined: Nov 2004 Posts: 843 Suffolk,VA I ireland383 super stock
ireland383 super stock I Joined: Nov 2004 Posts: 843 Suffolk,VA	Quote: I'm putting a 4.56 limited slip chunk in my 8 3/4. Primary use will be street. What oil wt. should I use (and why)? Also, what's a good limited slip additive? Is the additive Auto Zone sells any good? As far as additive I used Amsoil's Slip lock from Napa and for oil a GL-5 rated 80/90 will do.

Re: Rearend oil & limited slip additive? [Re: ireland383] #954262 03/20/11 07:07 AM 03/20/11 07:07 AM
Joined: Feb 2010 Posts: 18,493 Granite Bay CA Kern Dog Striving for excellence
Kern Dog Striving for excellence Joined: Feb 2010 Posts: 18,493 Granite Bay CA	Make sure you use the HYPOID rated oil too. It includes friction modifiers.

Re: Rearend oil & limited slip additive? [Re: T/A CARe] #954263 03/20/11 11:03 AM 03/20/11 11:03 AM
Joined: Nov 2003 Posts: 2,715 closer to Canadian beer! torkrules I'm neurotic
torkrules I'm neurotic Joined: Nov 2003 Posts: 2,715 closer to Canadian beer!	I've found the Royal Purple Max Gear works really well and it has the additive already there. I tried Lucas without the additive and at times the rear end sounded like there was something rolling around in the trunk everytime I turned a corner. As for the viscosity....whatever the gear manufacturer says or the FSM says. Failing that I would go 75/140 to be safe.

Re: Rearend oil & limited slip additive? [Re: Kern Dog] #954264 03/20/11 11:57 AM 03/20/11 11:57 AM
Joined: Nov 2007 Posts: 21,831 Kirkland, Washington Pacnorthcuda Too Many Posts
Pacnorthcuda Too Many Posts Joined: Nov 2007 Posts: 21,831 Kirkland, Washington	Quote: Make sure you use the HYPOID rated oil too. It includes friction modifiers. Not true. "Hypoid" refers to the cut of the gears. A "hypoid" lube (like GL-5) has specific extreme pressure additives, meant for ring & pinions--nothing to do with limited slips. A friction modifier is required for the limited slips, and some lubes have them in it, some do not.

Re: Rearend oil & limited slip additive? [Re: Pacnorthcuda] #954265 03/20/11 12:14 PM 03/20/11 12:14 PM
Joined: Jan 2007 Posts: 7,664 IN A ahy master
ahy master A Joined: Jan 2007 Posts: 7,664 IN	In terms of viscosity, OE called for 90 weight, now normally 80W-90. 75 or 85W-140 provides more high temp protection and more "cushion" at lower temps and likley causes a bit more friction and HP loss. Some racers have experimented with lighter lubes for slight ET improvments... I don't have a spare to throw in if mine breaks in an "experiment" so I'm running 85W-140 for the better protection as recommended by the builder of the rear. I've also used Autozone limited slip additive with good results (8.75 clutch type sure grip).

Re: Rearend oil & limited slip additive? [Re: ahy] #954266 03/20/11 02:51 PM 03/20/11 02:51 PM
Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska	Quote: In terms of viscosity, OE called for 90 weight, now normally 80W-90. 75 or 85W-140 provides more high temp protection and more "cushion" at lower temps and likley causes a bit more friction and HP loss. , Many choices & I'd think synthetic would b better (for all apps?) but I will defer to the rear end guy on that & some have the additive already in it & yes it's needed live every 24 hour block of time like it's your last day on earth

Re: Rearend oil & limited slip additive? [Re: Pacnorthcuda] #954267 03/20/11 03:53 PM 03/20/11 03:53 PM
Joined: Jan 2003 Posts: 18,425 UPPER MICHIGAN, MARQUETTE COUN... N NITROUSN I Live Here
NITROUSN I Live Here N Joined: Jan 2003 Posts: 18,425 UPPER MICHIGAN, MARQUETTE COUN...	Quote: Quote: Make sure you use the HYPOID rated oil too. It includes friction modifiers. Not true. "Hypoid" refers to the cut of the gears. A "hypoid" lube (like GL-5) has specific extreme pressure additives, meant for ring & pinions--nothing to do with limited slips. A friction modifier is required for the limited slips, and some lubes have them in it, some do not. Thats exactly right. A lot of companies say compatible with limited slip differentials. That does not mean the additive is in it. I buy all mine direct from the ford dealer parts department. Very good prices.

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