rearend fluid - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Low68 · 01-23-2003, 11:27 AM

I am putting a new diff cover on and am replacing the fluid. I have some full synthetic fluid and was told that if you use full synthetic fluid, you don't have to put that posi fluid stuff in. I don't know exactly what it is, but I know you have to put in some kind of fluid if you have posi. I don't have any of that stuff and don't want to get it if I don't have to. Anyone know? Thanks
Low68

crazy longhorn · 01-23-2003, 11:36 AM

You might check to see if the lube has an addative, but I am running Richmond syn in my 12 bolt, & no GM addative with a factory eaton unit......crazyL

**1971Stepside** · 01-23-2003, 01:04 PM

My new Eaton 3.73 posi came with a big warning sticker that said not to run synthetic oil in the rearend. It recommended 80-90W gear oil and the little bottle of posi lube came with the kit.

lukecp · 01-23-2003, 01:49 PM

The bottle of oil will say if it is reccomend for "conventional" (one-legger) or limited slip (positraction) differentials. Most oil is OK to use for both.

01-23-2003, 11:27 AM	#1
Low68 Registered User Join Date: May 2001 Location: Arizona Posts: 758	rearend fluid I am putting a new diff cover on and am replacing the fluid. I have some full synthetic fluid and was told that if you use full synthetic fluid, you don't have to put that posi fluid stuff in. I don't know exactly what it is, but I know you have to put in some kind of fluid if you have posi. I don't have any of that stuff and don't want to get it if I don't have to. Anyone know? Thanks Low68 __________________ Build Thread

01-23-2003, 11:36 AM	#2
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	You might check to see if the lube has an addative, but I am running Richmond syn in my 12 bolt, & no GM addative with a factory eaton unit......crazyL __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

01-23-2003, 01:04 PM	#3
1971Stepside Almost Satisfied Join Date: Mar 2002 Location: Springfield, MO Posts: 2,932	My new Eaton 3.73 posi came with a big warning sticker that said not to run synthetic oil in the rearend. It recommended 80-90W gear oil and the little bottle of posi lube came with the kit. __________________ 1971 C10 Stepside. LSx 6.0 with BTR Stage IV, Speed Engineering Headers, 4L80e transmission w/3200 Circle-D Stall. 3.73. Posi. Purchased this truck when I was 17. I started the rebuild (or take apart) in 1993. I have drug it around all over the country in pieces. Finally back on the road in 2021. "I can't complain, but sometimes I still do. Life's been good to me so far."

01-23-2003, 01:49 PM	#4
lukecp Formerly yellow72custom Join Date: May 2001 Location: Austin, TX Posts: 7,531	The bottle of oil will say if it is reccomend for "conventional" (one-legger) or limited slip (positraction) differentials. Most oil is OK to use for both. __________________ '72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg



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