Can you run Schaeffer 50W oil in a SM465?

[cvanerstrom04]

I have a build that I'm getting close to completion on. Its a 1983 Chevy c30 crew cab originally but has been 4wd swapped and ls swapped by me and I got a nice sm465 and np205 trans/t-case setup and I was wondering what oil I should run. I have a 5 gallon bucket left over of 50w Schaefer oil that I used in my G56 trans in my dodge. Can I run this in my sm465 or will it damage the transmission? also I am going to fill the transfer case, front axle (D44) and rear end (14bolt) and was wondering reasonably priced oil to run in these as well. Any input or information would be greatly appreciated!

 

[bucket]

I've got nothing to add here, I'm just in to see what the consensus is.

 

[mtnmankev]

In my opinion and experience, it seems the viscosity index MIGHT be okay if the climate was cold year round, otherwise probably too low for warm/hot weather, and I seriously doubt it's extreme pressure characteristics and any additives that might protect the gears and bearings.
On the plus side, gear oil STINKS and I have NEVER met anybody who actually liked the smell of it.
At least you won't have to deal with the stench that refuses to go away.

 

[Shorty81]

I use 80W-90 API GL5 Mineral oil. I would stay away from synthetic oil. Always worked well for me. Love Shaeffer oil in my crank case!!

 

[Ricko1966]

You should be using 80/90 gl4 in both, the gl5 is corrosive to some metals. There are different friction modifiers and extreme pressure additives in the gl4 than in motor oil. The extreme pressure capability would be why I'd use gl4.

 

[Shorty81]

You should be using 80/90 gl4 in both, the gl5 is corrosive to some metals. There are different friction modifiers and extreme pressure additives in the gl4 than in motor oil. The extreme pressure capability would be why I'd use gl4.

@Ricko1966 is right. GL4. Don't know what I was thinking....long day!!

 

[DoubleDingo]

Agreed on the GL4. 90w gear or mineral oil is the lubrication needed for the old manual transmissions

 

[bucket]

In my opinion and experience, it seems the viscosity index MIGHT be okay if the climate was cold year round, otherwise probably too low for warm/hot weather, and I seriously doubt it's extreme pressure characteristics and any additives that might protect the gears and bearings.
On the plus side, gear oil STINKS and I have NEVER met anybody who actually liked the smell of it.
At least you won't have to deal with the stench that refuses to go away.

The smell of gear oil doesn't bother me one bit. I won't go so far as to say it smells good, but I don't think it smells bad.

Now, used supercharger oil from a GM 3800 on the other hand...

 

[85K304SPD]

Go with the one that says Syncro Mesh on the label. I think it is Pennzoil. It wont eat the brass synchros.

 

[Ricko1966]

In my opinion and experience, it seems the viscosity index MIGHT be okay if the climate was cold year round, otherwise probably too low for warm/hot weather, and I seriously doubt it's extreme pressure characteristics and any additives that might protect the gears and bearings.
On the plus side, gear oil STINKS and I have NEVER met anybody who actually liked the smell of it.
At least you won't have to deal with the stench that refuses to go away.

FWIW viscosity ratings on gear oil is not the same rating as motor oil. I think 90w gear oil is the same viscosity as 50w motor oil. Not picking on you Kev, just sharing info for you and anyone else that wants/needs to know.

 

[mtnmankev]

I always thought that viscosity index ratings were based on the same criteria, different oils are different thickness and flow accordingly, and the only constant that doesn't change is gravity always applies.

 

[Ricko1966]

I always thought that viscosity index ratings were based on the same criteria, different oils are different thickness and flow accordingly, and the only constant that doesn't change is gravity always applies.

What you said makes sense to you and me. But not engineering geniuses. IDK why.

 

[DoubleDingo]

I believe gear oil has better shear qualities.

 

[Juggernaut]

When I had my SM465 rebuilt for the first time in the early 90's the builder told me to us SAE 50 ND. He told me the non detergent oil won't suspend the dirt in the oil. Dirt collects in the bottom of the case. Ran the transmission on the road until 2002 when I started bogging the truck, so it has seen some abuse. I tore it down in 2020, there was a lot of sludge in the bottom and around the magnet, but very little wear on the gears and syncro's. Only wear I had was from me grinding gears when throwing it in reverse

 

[Mark80K15]

So, it sounds like the consensus for SM465 is SAE-80W-90 GL4. But @AuroraGirl posted a picture from the 1980 owners manual on Oct 9, 2021 in the "2wd SM465 Speedo Gear Problems" forum, which shows SAE-80W-90 GL-5, or in Canada (like me), use SAE-80W GL-5. Why does the manual specify that if GL-5 is actually harmful?

Also, that forum seems to conclude 85W-90 GL-4 CRC gear oil should be used (what is CRC?). So that forum disputes this forum?

Do we have consensus? What about NP205? The same?