G80 Gear Oil?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

DanMcG

Full Access Member
Joined
Jun 28, 2014
Posts
1,076
Reaction score
1,881
Location
Central NY
First Name
Dan
Truck Year
1978 1985
Truck Model
k10 k10
Engine Size
400 350
I'm looking for some confirmation on the right lube to use in my 85 G80 locking differential.
I'm pretty sure this is the stuff.

Valvoline High Performance 80W-90 Conventional Gear Oil​



And what's the preferred method for sealing it back up gasket or RTV?
 
Last edited:

1979 c20

Full Access Member
Joined
Jun 28, 2022
Posts
369
Reaction score
172
Location
Oregon
First Name
Rat
Truck Year
1979
Truck Model
C20
Engine Size
454
I seem to remember that it called for a synthetic on the Tahoe I did axle seals on last year. I think I used rtv to button up.

Let's see what everyone else thinks about it.
 

nvrenuf

Full Access Member
Joined
Jul 30, 2010
Posts
1,685
Reaction score
1,869
Location
Mobile, Al.
First Name
John
Truck Year
1991
Truck Model
K5
Engine Size
454
Don’t these need L/S additive too?
 

DanMcG

Full Access Member
Joined
Jun 28, 2014
Posts
1,076
Reaction score
1,881
Location
Central NY
First Name
Dan
Truck Year
1978 1985
Truck Model
k10 k10
Engine Size
400 350
Don’t these need L/S additive too?
I don't know,...but I don't think so. Limited slip is different then a locking diff.
I'm really clueless about these things.
 

Juggernaut

Full Access Member
Joined
Apr 11, 2021
Posts
203
Reaction score
215
Location
Illinois
First Name
Greg
Truck Year
78
Truck Model
K20
Engine Size
350
The Valvoline 80/90 is what I use in my 14 bolt FF with G80. I have never added any additive. Still works after 34 years I have had it
 

nvrenuf

Full Access Member
Joined
Jul 30, 2010
Posts
1,685
Reaction score
1,869
Location
Mobile, Al.
First Name
John
Truck Year
1991
Truck Model
K5
Engine Size
454
Don’t the Gov Locks still have clutch packs on the sides (in addition to the locking mechanism)?
 

oldretiredafguy

Full Access Member
Joined
Apr 20, 2020
Posts
1,412
Reaction score
3,204
Location
N. Texas
First Name
Mike
Truck Year
1988, 1988, 1991, 1983
Truck Model
GMC V-Jimmy, GMC Suburban 4WD, GMC Suburban 4WD, GMC-2500 CrewCab
Engine Size
350, 350, 350, 350
I don't know if the Valvoline gear oil has the anti-friction modifier in the formula, but it's very cheap to add that 8oz bottle.
 

Turbo4whl

Supporting Member
Supporting Member
Joined
Oct 30, 2019
Posts
2,837
Reaction score
6,356
Location
Downingtown, PA
First Name
Wayne
Truck Year
1974
Truck Model
Jimmy
Engine Size
350
No limited slip additive needed. No friction modifiers either. Newer trucks like @1979 c20 Tahoe calls for synthetic because the seals are for synthetic. Regular 80w90 is what you want.
 

Latest posts

Forum statistics

Threads
41,854
Posts
903,556
Members
33,367
Latest member
texdave
Top