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| | | Joined: Apr 2005 Posts: 396 Shop Shark | | Shop Shark Joined: Apr 2005 Posts: 396 | I have asked here about using it in the steering gear box and it seems to work good there. What if I were to fill my SM420 transmission with it? Would I run into problems? What about the rear end? I have that elusive HO72 with 4:11 gears and would hate to ruin that one as they are near impossible to find anymore.I only drive the truck in the summer, Never out there in Minnesota Cold , snow, Ice etc.This past winter in Minnesota it seemed was almost Forever. Some say Minnesota winter is 9 months of Tough Sledding! Then it is 3 months of road construction. The truck is usually in my heated shop over winter with me working on the projects I want completed for the next year. Jerry
Jerry
| | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | Why?
The grade of oil for that transmission is specified by GM. SAE 90 (with SAE 80 being OK in the winter).
Steering gear grease is a muck thicker lubricant than specified by GM for use in that transmission.
| | | | | Joined: Jan 2010 Posts: 120 Shop Shark | | Shop Shark Joined: Jan 2010 Posts: 120 | SM420 and diff want 90 grade hypoid. Corn head grease is 600 grade and I would say it would cavitate out of the working surfaces and you would wreck things. Yes perfect for the steering box only.
'47 Canadian RHD 1.5 ton truck
| | | | | Joined: Oct 2013 Posts: 219 Shop Shark | | Shop Shark Joined: Oct 2013 Posts: 219 | My 2 pennies worth... I use GL4 in my SM420 and Rear diff. The parts house guys might tell you GL5 is better but it is not. SM420s have brass components in them and GL5 contains salt that will leach away your metals. You need to order GL4 company direct and it is a little more pricey but it will quiet it down a bit and shift like butter.
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