Thinnest gear oil???
#2993053
12/07/21 09:56 PM
12/07/21 09:56 PM
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Joined: Jan 2005
Posts: 12,419 Kalispell Mt.
HotRodDave
OP
I Live Here
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OP
I Live Here
Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
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What is the thinnest oil that would work at least somewhat adequate in a 8.25 open diff in a light weight very low power kind of car? Just thinking about doing some more MPG experiments and was wondering if I could use something lighter like slick-50 or maybe ATF+4 since they use it in FWD auto tranns with differential gears in them. Not nessacarily looking for 200,000 miles out of it but if I could get 50,000 - 100-000 miles out of one.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: Thinnest gear oil???
[Re: HotRodDave]
#2993077
12/07/21 10:52 PM
12/07/21 10:52 PM
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Joined: Dec 2004
Posts: 10,552 Rittman Ohio
fourgearsavoy
I Live Here
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I Live Here
Joined: Dec 2004
Posts: 10,552
Rittman Ohio
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I would go to maybe a straight 30 wt. motor oil. That is what Honda used to use in their manual gear boxes. Gus
64 Plymouth Savoy 493 Indy EZ's by Nick at Compu-Flow 5-Speed Richmond faceplate Liberty box Dana 60
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Re: Thinnest gear oil???
[Re: HotRodDave]
#2993095
12/08/21 01:37 AM
12/08/21 01:37 AM
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Joined: Jul 2008
Posts: 607 Boise
Moparteacher
mopar
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mopar
Joined: Jul 2008
Posts: 607
Boise
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Motor oil may work, but hypoid cut gears found in the 8.25" differential require difference properties than helical or straight cut gears found in manual transmissions and transaxles. If it's relatively light duty application then a good motor oil might last. If it's an experiment then go I wouldn't bother with slick 50. I would go straight to a 0w20. The 80w90 gear oil has approximately the same viscosity as 30w or 40 w sae motor oil. Take a looky. https://www.kewengineering.co.uk/Auto_oils/oil_viscosity_explained.htm
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Re: Thinnest gear oil???
[Re: Moparteacher]
#2993106
12/08/21 03:12 AM
12/08/21 03:12 AM
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Joined: Aug 2003
Posts: 43,128 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,128
Bend,OR USA
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I know a well known and accomplished drag racer that ruined a set of fairly new 4:86 gears in his 1971 Dodge Demon 8 3/4 in one run trying either 30 or50 Wt. racing oil in the rear end for one run I use ATF in my NP833 18 spline pro shifted drag racing 4 speed for 2 1/2 years in my old 1970 Hemi Cuda, worked good, lasted a long time I would change it about every 40 runs after doing maintenance on the gears and sliders
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Thinnest gear oil???
[Re: topside]
#2993220
12/08/21 01:38 PM
12/08/21 01:38 PM
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Joined: Jan 2003
Posts: 5,894 Florida
Locomotion
master
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master
Joined: Jan 2003
Posts: 5,894
Florida
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In some cases there is always the option of running less of the proper, but lighter viscosity gear oil, to reduce friction/windage. Testing would involve figuring out what the minimum amount is. Some have told me that 1 quart is enough in an 8 3/4 application, but don't know if that's for limited runs or constant. I never tried less than 1 1/2 qts. for limited runs (drag racing). I'm sure there would be a difference between a spooled or open rear compared to a Sure Grip equipped differential.
Last edited by Locomotion; 12/08/21 01:42 PM.
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