SM465 fluid - i used gear lube, maybe synthetic gear lube - what now

[AuroraGirl]

I was reading about how you should use mineral oil in a sm465 instead of gear lube. 4 years ago i put new fluid in the transmission and i followed the manual which called for gear lube, but it was supertech brand that may have been synthetic.

THe trans definitely shifts better now that the engine runs right and the fluid was replaced, but L and R will make a whinning noise thats directly variable to speed, but they are less severe than the past. If that means anything. They do move fine and shift into gear fine, sometimes requires a little persuasion to push into L or R but nothing bad.

 

[MrMarty51]

The old four speed units all used motor oil, or so I`m a thinking. If not the Montana DOT been doing it all wrong for a lot of years. LOL
I know the newer overdrive units uses some kind of a friction modified stuff to allow the synchros to properly function.
Might be someone will come in and correct My way of thinking.

 

[71RAT]

SM465 is a pretty rugged transmission. That being said they are not the slickest shifting manual transmission, by any means.
We use the Red Line MT-90 or 75 90 NS, in a lot of the older manuals. Auto Gear likes Driven racing oil, but that's harder to find.

 

[WFO]

The SM465 should use the hard to find GL-4 lube. GL-5 or newer lubes can be corrosive to the synchronizers in older type transmissions.

 

[Grit dog]

You’ve been using the oil 4 years and it shifts better.
What’s the question?
It’s an old gearbox full of not old oil. It’s fine.

 

[AuroraGirl]

I was told it could be detrimental. Id prefer something that isnt And its more like its been sitting for 3 years used for 1 year periodically.

 

[HotRodPC]

I was reading about how you should use mineral oil in a sm465 instead of gear lube. 4 years ago i put new fluid in the transmission and i followed the manual which called for gear lube, but it was supertech brand that may have been synthetic.

THe trans definitely shifts better now that the engine runs right and the fluid was replaced, but L and R will make a whinning noise thats directly variable to speed, but they are less severe than the past. If that means anything. They do move fine and shift into gear fine, sometimes requires a little persuasion to push into L or R but nothing bad.

I'd say the whine is likely normal. I mean, we don't get to hear it, but those 2 gears are low enough, that the rpms vs the counter gear are spinning much faster than the other gears and they'll be nosier by default. Kinda of like a spinning a top. You put a spin on it, it makes a little noise, you really crank it up and put a real fast spin on it, it whines louder. I'd say it's gear ratio related most likely and normal if it's not much louder than the other gears. A little persuation is normal too. As said, they're spinning faster and the synchros have to slow them down. Whenever you feel the persuation needed, let the clutch up a hair, not to fully engage but just enough to synch the rpms with the engine and you'll feel it suck it right on it there without persuation.

 

[SquareRoot]

Be happy your not talking about an nv4500. Don't get me started.

 

[DoubleDingo]

The SM465 should use the hard to find GL-4 lube. GL-5 or newer lubes can be corrosive to the synchronizers in older type transmissions.

^^^THIS^^^

Use mineral oil from Napa, they sell it by the gallon.

 

[eskimomann209]

Be happy your not talking about an nv4500. Don't get me started.

LMFAO. Even shops **** this one up.

OP, If you followed the manual I think you should be alright. The argument vs synthetic and non synthetic gets tiresome. Some even label their stuff as synthetic and it isn’t.
If it’s running and isn’t making a ton of scary noises, I’d run it.

 

[Lu Blunt]

I’ve had good experience with brad penn gl-4 80w-90 gear oil. Supposed to safe for brass bronze and copper synchros. looks like they changed the label but here’s the summit link

https://www.summitracing.com/parts/bpo-77296

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[AuroraGirl]

^^^THIS^^^

Use mineral oil from Napa, they sell it by the gallon.

I have an old jug of mineral oil, but its gotta be 20 years old and its opened. So I think Ill stop by NAPA next time im in town, Ive been working a lot of hours. Is mineral oil like gear lube but gl-4? I guess Im not sure what defines something mineral oil vs gear lube.

Be happy your not talking about an nv4500. Don't get me started.

What do you mean? Im sorry to get you started, but I guess Im not sure of what your hinting at. Is it very specific about the fluid you put in it?

 

[AuroraGirl]

I'd say the whine is likely normal. I mean, we don't get to hear it, but those 2 gears are low enough, that the rpms vs the counter gear are spinning much faster than the other gears and they'll be nosier by default. Kinda of like a spinning a top. You put a spin on it, it makes a little noise, you really crank it up and put a real fast spin on it, it whines louder. I'd say it's gear ratio related most likely and normal if it's not much louder than the other gears. A little persuation is normal too. As said, they're spinning faster and the synchros have to slow them down. Whenever you feel the persuation needed, let the clutch up a hair, not to fully engage but just enough to synch the rpms with the engine and you'll feel it suck it right on it there without persuation.

Well I know L and R arent synchronized, at least thats my understanding, and have found the clutch trick to help it a bit. But I guess the shear loudness of the reverse gear, which seems a tad worse than Low, but 1st(2nd) makes no noise. I dont actually know how 2nd and 3rd sound too much, I dont ever get into those gears. I have used 2nd, but for only 5 to 10 seconds max haha. Isnt reverse a similar gear ratio to 1st?

 

[SquareRoot]

I have an old jug of mineral oil, but its gotta be 20 years old and its opened. So I think Ill stop by NAPA next time im in town, Ive been working a lot of hours. Is mineral oil like gear lube but gl-4? I guess Im not sure what defines something mineral oil vs gear lube.


What do you mean? Im sorry to get you started, but I guess Im not sure of what your hinting at. Is it very specific about the fluid you put in it?

Yes. It has carbon fiber syncros that use a very specific synthetic fluid that is almost impossible to find anymore. If you put regular gear oil in it, it's game over. I have two nv 4500's and one was properly maintained and one wasn't. I found the correct fluid, but it goes for about $23/quart. The upside is, the 4500 is considered to be the most durable, smooth shifting, 5 speed overdrive manual trans GM ever made. We shall see.

 

[HotRodPC]

Those aren't the most quiet gearboxes by default. Normally when you have a noisy gearbox due to a bad bearing, especially input shaft bearing, it'll be real noisy in all gears EXCEPT whatever gear is your 1 to 1 ratio. Reason that is, is because at the 1 to 1 ratio, the gears and shaft are almost just straight through the center of the transmission and no side torque strain to speak of. So it's probably just normal heavy duty transmission gear noise you're hearing is my guess.