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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Rear Drivelines, Drive Axles and Gearing => Topic started by: GUITAR1989 on February 03, 2011, 11:04:14 pm

Title: 12 bolt rear end...what kind of gear lube to use? :)
Post by: GUITAR1989 on February 03, 2011, 11:04:14 pm

Hey guys I need to change the fluid in my trucks rear end :) I was just wondering what kind of gear lubricant to use. The rear end is a GM 12 bolt. Thanks for your time
 Shayne

Title: Re: 12 bolt rear end...what kind of gear lube to use? :)
Post by: SAATR on February 03, 2011, 11:30:21 pm

Likely a 75w90 or an 80w90.  I like Royal Purple and Valvoline Durablend, both have served me well in the past.  If you have a clutch type posi, be sure to put some limited slip additive in first to prevent it from chattering.

Title: Re: 12 bolt rear end...what kind of gear lube to use? :)
Post by: Grim 82 on February 04, 2011, 12:04:40 am

+1
80w90. I've been using synthetic Valvoline on my last few trucks with good results. If you have a performance diff figure out what you have and use the oil or additive you need for that application.

Title: Re: 12 bolt rear end...what kind of gear lube to use? :)
Post by: GUITAR1989 on February 04, 2011, 12:14:14 am

nice thanks guys. I think what my truck has is called open differential..When I have the rear jacked up I can spin a wheel and the other one doesnt move. Does that need an additive?

Title: Re: 12 bolt rear end...what kind of gear lube to use? :)
Post by: Grim 82 on February 04, 2011, 12:56:19 am

You probably have a stock open diff, so you can just use a conventional oil. Pop the cover and if it has all kinds of gadgets in there take a pic and we can tell you if it's something different.