What Oil to Run in 12Bolt - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**1971Stepside** · 11-12-2002, 06:14 PM

My new 3.73 Posi, Ring and Pinion should be here via Brown today and the guy that is doing the set up for me recommended a 80 - 90 weight oil named Mystick JT7. He said that they have run this oil for years in his race cars and it will make the rearend run much cooler than conventional oils. It is not a synthetic however.

What are you guys running? Would you recommend a synthetic with the locker? It is a Eaton locker.

Thanks

crazy longhorn · 11-12-2002, 06:31 PM

I am running 75/140 Richmond synthetic in the longhorn. Thats a 12 bolt posi, with richmond 4.10 gears(factory eaton unit)

my new 72 · 11-12-2002, 06:42 PM

Mobil 1 90wt Synthetic. Nothing Better

11-12-2002, 06:14 PM	#1
1971Stepside Almost Satisfied Join Date: Mar 2002 Location: Springfield, MO Posts: 2,932	What Oil to Run in 12Bolt My new 3.73 Posi, Ring and Pinion should be here via Brown today and the guy that is doing the set up for me recommended a 80 - 90 weight oil named Mystick JT7. He said that they have run this oil for years in his race cars and it will make the rearend run much cooler than conventional oils. It is not a synthetic however. What are you guys running? Would you recommend a synthetic with the locker? It is a Eaton locker. Thanks __________________ 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."

11-12-2002, 06:31 PM	#2
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	I am running 75/140 Richmond synthetic in the longhorn. Thats a 12 bolt posi, with richmond 4.10 gears(factory eaton unit) __________________ 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....

11-12-2002, 06:42 PM	#3
my new 72 faster, faster, faster Join Date: Dec 2001 Location: Houston ,Texas ,USA Posts: 1,354	Mobil 1 90wt Synthetic. Nothing Better __________________ I'm going to Law School, wanna debate? It's good practice.



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