Gear oil for a posi rear end - The 1947 - Present Chevrolet & GMC Truck Message Board Network

cdcd · 04-15-2002, 01:26 AM

What's the recommended oil to use in the rear diff with a posi unit?

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72 c-10 lwb 350/4speed/3.73 posi

71GMC_3/4T · 04-15-2002, 08:47 AM

Chevy Garage has the stuff. Not sure of the P/N and I remember it wasn't exactly cheap.

71Chev · 04-15-2002, 08:51 AM

Not sure if you need the additive for your posi, but my 96 required it. I got the gearlube and the additive for my 96 from the dealer.

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71 Chevy CST Long Fleet 350/350/3.07 leaf rear.

Norwegian · 04-15-2002, 09:11 AM

In the drivers manual for my GMC truck 910 from 68 it saies you need a special oil with pn. 5786991. I wonder if the number is stil in use?

**MJN** · 04-15-2002, 10:08 AM

Use 80-90 gear lube with the GM posi additive. If you don't use the additive then the clutches wear and the posi will clunk and make noise. I added it to my '72 and it quieted down and works much smoother.

cdcd · 04-16-2002, 01:18 AM

Thanks for the input.

ddsmith · 04-16-2002, 04:42 AM

This is a very important subject. Here is a little of my history. I changed the rear end oil in my Corvette. I used an oil which claimed it was for GM posi rear and then the bad stuff started happening. I was young and thought that the rear end needed to be replaced because I would have to rev the 454 up to 2000 rpm when pulling away from a stop sign and turning. The cause was improper lubricant gumming up the clutch packs. I remeber my suprise when the Chevy dealer said it was ready for pickup and the price was like $30.00. Okay it was a long time ago. All they did was flush the rear out and put in the right gear lube. I think I have some in the garage. Special lube is GM1052271 and the additive is GM1052358. This is what was called out for my 87 Firebird or the Vette but I think you'll find this might also be correct for other limited-slip rears. The no-spin rear is a different story. I'm pretty sure you use 80-90 gear lube for that application. No clutch pack to worry about.

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66 Chevy C30 Stakebody Dump, PS,PB, 327cu in
71 Corvette Coupe 454 4 speed
79 Chevy 4X4 (Tom's old truck)

04-15-2002, 01:26 AM	#1
cdcd Registered User Join Date: May 2000 Location: New Mexico Posts: 32	Gear oil for a posi rear end What's the recommended oil to use in the rear diff with a posi unit? ------------------ 72 c-10 lwb 350/4speed/3.73 posi __________________ 72 c-10 lwb 350/4speed/3.73 posi

04-15-2002, 08:47 AM	#2
71GMC_3/4T Weapons Of Construction Join Date: Apr 2000 Location: Colorado, USA Posts: 1,095	Chevy Garage has the stuff. Not sure of the P/N and I remember it wasn't exactly cheap. __________________ 1971 GMC 2500, 402/TH400 4.10 Daily Driver Lafayette, CO

04-15-2002, 08:51 AM	#3
71Chev Senior Member Join Date: Dec 2000 Location: Indiana Posts: 3,074	Not sure if you need the additive for your posi, but my 96 required it. I got the gearlube and the additive for my 96 from the dealer. ------------------ 71 Chevy CST Long Fleet 350/350/3.07 leaf rear. __________________ 71 Chevy CST Long Fleet 350/350/3.07 leaf rear.

04-15-2002, 09:11 AM	#4
Norwegian Registered User Join Date: Mar 2002 Location: Andenes, Norway Posts: 16	In the drivers manual for my GMC truck 910 from 68 it saies you need a special oil with pn. 5786991. I wonder if the number is stil in use? __________________ 75 Blazer K5 cab 66 Chevrolet Impala 2dht 68 GMC 4x4 pickup (project) 43 GMC CCKW 6x6

04-15-2002, 10:08 AM	#5
MJN Registered User Join Date: Feb 2000 Location: Maquoketa, Ia/ Orr, Mn Posts: 2,967	Use 80-90 gear lube with the GM posi additive. If you don't use the additive then the clutches wear and the posi will clunk and make noise. I added it to my '72 and it quieted down and works much smoother. __________________ '51 South Bend Model "9A" '56 Chevy 3600 NAPCO '74 Chevy Cheyenne Super K20-restored on 37's '72 GMC Sierra Custom K2500- in progress '08 GMC Envoy Denali '12 GMC Sierra 2500HD Denali '17 GMC Yukon XL VCCA member #58596 http://www.nohrco.com

04-16-2002, 01:18 AM	#6
cdcd Registered User Join Date: May 2000 Location: New Mexico Posts: 32	Thanks for the input. __________________ 72 c-10 lwb 350/4speed/3.73 posi

04-16-2002, 04:42 AM	#7
ddsmith Glowing since 1978 Join Date: Mar 2001 Location: Lusby,MD,USA Posts: 532	This is a very important subject. Here is a little of my history. I changed the rear end oil in my Corvette. I used an oil which claimed it was for GM posi rear and then the bad stuff started happening. I was young and thought that the rear end needed to be replaced because I would have to rev the 454 up to 2000 rpm when pulling away from a stop sign and turning. The cause was improper lubricant gumming up the clutch packs. I remeber my suprise when the Chevy dealer said it was ready for pickup and the price was like $30.00. Okay it was a long time ago. All they did was flush the rear out and put in the right gear lube. I think I have some in the garage. Special lube is GM1052271 and the additive is GM1052358. This is what was called out for my 87 Firebird or the Vette but I think you'll find this might also be correct for other limited-slip rears. The no-spin rear is a different story. I'm pretty sure you use 80-90 gear lube for that application. No clutch pack to worry about. ------------------ 66 Chevy C30 Stakebody Dump, PS,PB, 327cu in 71 Corvette Coupe 454 4 speed 79 Chevy 4X4 (Tom's old truck) __________________ 66 Chevy C30 Stakebody Dump, PS,PB, 327cu in 71 Corvette Coupe 454 4 speed 69 Chevy C20 Custom Camper



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