Proper gear lube for Muncie SM465 with brass - The 1947 - Present Chevrolet & GMC Truck Message Board Network

CCCC · 12-12-2017, 06:37 PM

After rebuilding the transmission I filled it with the proper weight/rating gear lube. Later noticed that the container was labeled "GL-5 rated". Now i have seen that the GL-5 lube will be hard on the brass synchros in there - supposedly will eat them up. The lube has been in there for a few weeks, but have driven the truck only about 50 miles.

I will change the lube as soon as possible, but so far have not been able to find the older GL-4 lube at any of our independent parts stores or at the "duh" chain stores. I did find LUCAS Universal Hydraulic and Transmission Fluid and the label says "meets API GL-4" requirements.

Two questions for those in the know:
1. Is that Lucas product good and proper for this Muncie with brass synchros?
2. How much "damage" might I expect to that brass from this short period/usage?

Thanks for any help>

homemade87 · 12-12-2017, 07:23 PM

Take a look at the bottle and see if it has w/ mt1 additive in it . If it does then your ok . This additive is for things that have brass in them . I still did not like using it because it still has the additive for posi rears .

I use brad penn gl-4 in my muncie . I get it at summit. This one is specifically made for this . I like you was not able to find anything suitable from the local places .

Unfortunate if you truly have the wrong stuff in there , there is no way to get it off the parts until it is tour down and cleaned . This I was told by autogear who makes the super case muncies which I have .

Here you go . I found it but it looks like they have renamed it to penngrade . https://www.summitracing.com/parts/bpo-023-7729

CCCC · 12-12-2017, 11:30 PM

Thanks homemade87 - I copied the info on the PennGrade and will order that if I can't find GL-4 in the big city next week. Will also look for the "w/mt1" designation on the Lucas product - maybe that one will work.

This situation is a pain, and I'm not going to remove and tear down that gearbox again. Maybe I will simply drain the GL-5 from the case, fill it with the best solvent I can ID and, after it sits for a while, run the trans slowly with the rear wheels up - go through all gears for a few minutes. Then quickly drain it and let it dry our before i install the proper lube.

With all of the old Chevs/GMCs I've had - and have - hard to accept believe I had never learned this about GL-5. Thanks again.

Does anyone out there use the Lucas product I mentioned? Anyone else have a thought?

Alex V. · 12-13-2017, 10:54 AM

I've owned multiple older stick shifts I'm sure had GL5 in them - even some I put GL5 in before I knew any better. I won't say they couldn't have worked better, but they were always satisfactory. Amsoil, Sta-Lube, and others make GL4 oils - my local Napa keeps the Sta-Lube and Amsoil is really good stuff.

12-12-2017, 06:37 PM	#1
CCCC Registered User Join Date: Mar 2007 Location: San Pedro River, SE Arizona Posts: 734	Proper gear lube for Muncie SM465 with brass After rebuilding the transmission I filled it with the proper weight/rating gear lube. Later noticed that the container was labeled "GL-5 rated". Now i have seen that the GL-5 lube will be hard on the brass synchros in there - supposedly will eat them up. The lube has been in there for a few weeks, but have driven the truck only about 50 miles. I will change the lube as soon as possible, but so far have not been able to find the older GL-4 lube at any of our independent parts stores or at the "duh" chain stores. I did find LUCAS Universal Hydraulic and Transmission Fluid and the label says "meets API GL-4" requirements. Two questions for those in the know: 1. Is that Lucas product good and proper for this Muncie with brass synchros? 2. How much "damage" might I expect to that brass from this short period/usage? Thanks for any help> __________________ CCCC 67 Sting Ray Coupe 327 4sp; 68 K10 Suburban 327 4sp; 69 K20 Lifted 383 4sp; 69 C80 Fire Truck 478 V6 5sp/2sp; 69 C20 Longhorn 327 4sp; 70 C30 Wrecker 350 4sp; 70 C30 Flat Bed 350 4sp; 71 C20 LWB 350 4sp; 72 K5 Blazer 350 4sp; 72 C30 Flat Bed Gooseneck Hauler with sleeper 350/TH400; 72 C20 Longhorn 402 4sp; 52 Mack LTL Supercharged Cummins 5sp x 3sp; 01 Dodge 5.9 HO Cummins 6spd; 02 Safari Trek 2430 8.1 Vortec on Workhorse Chassis; 03 Silverado 2500 HD 4wd Duramax/Allison Moved but still in the family 70 C20 Custom Camper 350/TH350; 72 K5 Blazer CST Highlander 350/TH350 Recently sent to new homes 72 C30 MoHome 402 4sp; 72 K5 Blazer Conv 350 4sp; 75 GMC 6000 Aerial 350 w Allison; 72 GMC 3500 Utility 350 4sp; 70 GMC 3500, 350 4sp

12-12-2017, 07:23 PM	#2
homemade87 Registered User Join Date: Apr 2010 Location: Guntersville Alabama Posts: 1,073	Re: Proper gear lube for Muncie SM465 with brass Take a look at the bottle and see if it has w/ mt1 additive in it . If it does then your ok . This additive is for things that have brass in them . I still did not like using it because it still has the additive for posi rears . I use brad penn gl-4 in my muncie . I get it at summit. This one is specifically made for this . I like you was not able to find anything suitable from the local places . Unfortunate if you truly have the wrong stuff in there , there is no way to get it off the parts until it is tour down and cleaned . This I was told by autogear who makes the super case muncies which I have . Here you go . I found it but it looks like they have renamed it to penngrade . https://www.summitracing.com/parts/bpo-023-7729 Last edited by homemade87; 12-12-2017 at 07:36 PM.

12-12-2017, 11:30 PM	#3
CCCC Registered User Join Date: Mar 2007 Location: San Pedro River, SE Arizona Posts: 734	Re: Proper gear lube for Muncie SM465 with brass Thanks homemade87 - I copied the info on the PennGrade and will order that if I can't find GL-4 in the big city next week. Will also look for the "w/mt1" designation on the Lucas product - maybe that one will work. This situation is a pain, and I'm not going to remove and tear down that gearbox again. Maybe I will simply drain the GL-5 from the case, fill it with the best solvent I can ID and, after it sits for a while, run the trans slowly with the rear wheels up - go through all gears for a few minutes. Then quickly drain it and let it dry our before i install the proper lube. With all of the old Chevs/GMCs I've had - and have - hard to accept believe I had never learned this about GL-5. Thanks again. Does anyone out there use the Lucas product I mentioned? Anyone else have a thought? __________________ CCCC 67 Sting Ray Coupe 327 4sp; 68 K10 Suburban 327 4sp; 69 K20 Lifted 383 4sp; 69 C80 Fire Truck 478 V6 5sp/2sp; 69 C20 Longhorn 327 4sp; 70 C30 Wrecker 350 4sp; 70 C30 Flat Bed 350 4sp; 71 C20 LWB 350 4sp; 72 K5 Blazer 350 4sp; 72 C30 Flat Bed Gooseneck Hauler with sleeper 350/TH400; 72 C20 Longhorn 402 4sp; 52 Mack LTL Supercharged Cummins 5sp x 3sp; 01 Dodge 5.9 HO Cummins 6spd; 02 Safari Trek 2430 8.1 Vortec on Workhorse Chassis; 03 Silverado 2500 HD 4wd Duramax/Allison Moved but still in the family 70 C20 Custom Camper 350/TH350; 72 K5 Blazer CST Highlander 350/TH350 Recently sent to new homes 72 C30 MoHome 402 4sp; 72 K5 Blazer Conv 350 4sp; 75 GMC 6000 Aerial 350 w Allison; 72 GMC 3500 Utility 350 4sp; 70 GMC 3500, 350 4sp

12-13-2017, 10:54 AM	#4
Alex V. Registered User Join Date: Mar 2013 Location: Campbellsville, KY Posts: 888	Re: Proper gear lube for Muncie SM465 with brass I've owned multiple older stick shifts I'm sure had GL5 in them - even some I put GL5 in before I knew any better. I won't say they couldn't have worked better, but they were always satisfactory. Amsoil, Sta-Lube, and others make GL4 oils - my local Napa keeps the Sta-Lube and Amsoil is really good stuff. __________________ Alex V. ------ 1967 C10 Suburban, 350/NP435, Green/Green, PS, PB, HD cooling, charging, shocks, and springs. 1985 GMC C3500 SRW, Sierra Classic, 454/TH400, white/blue.



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