SM465 Gear Oil Question

[Desert_Eagle02]

Hey guys, I'm going to change the gear oil in my SM465 trans and my NP205 t-case. I picked up 7 quarts of Valvoline High Performance 80W-90 gear oil. That's what I read that they took after doing a bit of research.

Anyway looking at the back of the bottle it says
"Designed for use in non-synchronized manual transmissions where GL-5 is specified and for hypoid differentials where API GL-4 or GL-5 is specified."

"Differential: API Service GL-4, GL-5
Non-Synchronized Manual Transmission: API Service GL-5"

So can I use it in my SM465 since it is synchronized? Or should I pick up something else?

Thanks

[kwmech]

80-90 will work just fine

[Desert_Eagle02]

Well I talked to Valvoline and they said that it being GL-5 and hypoid it could corrode and damage the sychros in the trans so they recommended not using it. It is good to go in the t-case and differentials though, so I will use it for that.

So I'm going to pick up some 80W-90 GL-4 for the transmission just to be on the safe side.

[andyh1956]

The crap they write on containers is maddening! I have gone thru this with the petroleum manufacturing people & they swear it aint them doing it but the containers will be marked GL4 & GL5 compatible!
It's either GL5 for Hypoid gears or it's GL4 for transmissions!
Here is a PDF Tutorial I had for you to save for future reference. It is from, of all places a Corvair Forum but read between the lines & the info will apply to our trucks as well as the lowly Corvair.
But anyway rant over your on the right path!
http://www.widman.biz/uploads/Transaxle_oil.pdf

[tucsonjwt]

I topped off my 83 C20 SM465 about 16 years ago with Autozone 80/90 gear oil and have not done anything to it since. I am considering a drain and refill since the PTO covers are leaking a bit. So, I guess I will look for GL-4 for the fill up.

[Desert_Eagle02]

Thanks for the PDF, I saved it for future reference.

Yeah I was all ready to change the oils today and for some reason decided to read the back of the containers. The reason I bought it is because it said "meets or exceeds API Services GL-5 or GL-4", so I thought it was good to go. But on the back it says "For non-synchronized manual transmissions." Good thing I questioned it and did further research. Pretty confusing if you ask me, and should be a lot more straight forward to people who aren't in the know with oil types. I was pretty irritated about it, but at least I can still use it in my t-case and differentials. I'd also rather be irritated for a bit than ruining my transmission haha.

I looked and called around local auto parts stores and nobody carries GL-4, so I ended up ordering Joe Gibbs Driven GL-4 gear oil safe for yellow metals and synchros.

For future reference to those that need it, from what I can find for who makes GL-4 gear oil safe for our manual transmissions, (I'm sure they may be others) are these

Coventional:
Joe Gibbs Driven GL-4
Brad Penn PennGrade GL-4

Synthetic:
Amsoil GL-4
Redline GL-4

[Jeepwm69]

NAPA usually carries GL4, FYI.

[hatzie]

Just look in the Maintenance and Lubrication section of the GM service manual for the GM recommended fluids...

From the 1987 Service Manual;
3-Speed (RPO M62 and M64) & 4-Speed (RPO M20) | SAE-80W GL-5 or SAE-80W-90 GL-5 gear lubricant GM part No. 1052271 (use SAE-80W GL-5 in Canada)

**Edit**
It's worth noting that even the 1973 Service Manual also calls for SAE 80 or SAE 90 GL-5 in the manual transmissions. The GM Engineers, being fairly conservative on things, apparently didn't trust multi-weight gear oils in 1972 when they put the 1973 manual together. They did call for the GL-5 rating straight through 1991 in the squarebody service manuals.

The engineers at GM called for GL-5 in the SM465 and Saginaw 3 speeds in these trucks. We aren't talking about a pre-1993 VW/Porsche/Audi/Skoda/Seat or antique GM Corvair or some other vehicle that the MFG called for GL-4 in the transmission/transaxle. I would use what the MFG called for.

The first half of this thread on Bob Is The Oil Guy about GL-4 & GL-5 oils is fairly informative... Page down to what Road Rage has to say for a distillation. Shortly after his post it devolves into off-topic religious arguments about what oil to use in more modern transmissions like the T56, NV3500, and NV4500 https://www.bobistheoilguy.com/forum...06251&page=all
GL-5 oils from major petrochemical companies, at this late date, should no longer have active sulfur compounds. The folks on BITOG agree with homemade87. API MT-1 certification means you can be positive they are yellow metal safe.
**Edit**

[homemade87]

If it has this MT-1 listed on the back label its supposed to be fine for yellow metals . I have used the valvoline with the MT-1 in my muncies with no problem but since then I have used PennGrade Multipurpose Classic GL-4 Gear Oil 77296 .This is made specifically for brass or yellow metals .

Gl-4 in parts store is hard to fine since what they have is rated for both . I guess the dont stock it for a couple reasons . Double inventory and less demand .

If using the dual rated just be sure it has the MT-1 listed on the back of the bottle .

[andyh1956]

Originally Posted by hatzie

Just look in the Maintenance and Lubrication section of the GM service manual for the GM recommended fluids...

From the 1987 Service Manual;
3-Speed (RPO M62 and M64) & 4-Speed (RPO M20) | SAE-80W GL-5 or SAE-80W-90 GL-5 gear lubricant GM part No. 1052271 (use SAE-80W GL-5 in Canada)

**Edit**
It's worth noting that even the 1973 Service Manual also calls for SAE 80 or SAE 90 GL-5 in the manual transmissions. The GM Engineers, being fairly conservative on things, apparently didn't trust multi-weight gear oils in 1972 when they put the 1973 manual together. They did call for the GL-5 rating straight through 1991 in the squarebody service manuals.

The engineers at GM called for GL-5 in the SM465 and Saginaw 3 speeds in these trucks. We aren't talking about a pre-1993 VW/Porsche/Audi/Skoda/Seat or antique GM Corvair or some other vehicle that the MFG called for GL-4 in the transmission/transaxle. I would use what the MFG called for.

The first half of this thread on Bob Is The Oil Guy about GL-4 & GL-5 oils is fairly informative... Page down to what Road Rage has to say for a distillation. Shortly after his post it devolves into off-topic religious arguments about what oil to use in more modern transmissions like the T56, NV3500, and NV4500 https://www.bobistheoilguy.com/forum...06251&page=all
GL-5 oils from major petrochemical companies, at this late date, should no longer have active sulfur compounds. The folks on BITOG agree with homemade87. API MT-1 certification means you can be positive they are yellow metal safe.
**Edit**

It might be interesting to note after your post to point out that the 4 speed used in the Corvair was a regular Muncie 4 speed trans! The madness continues!
The info about MT 1 is good info, thanks. None of the petroleum engineers I have talked to in several years has mentioned this.
Reason for being in contact with them is for the old T84 & T90 series Warner transmissions used in Jeeps. I typically find yellow oil & corroded sycros in these trans when broken down. Could very well be water contamination as well, or a combo.

[hatzie]

The Corvair transmission was not a regular 4 speed Muncie transmission. It was a transaxle for an air cooled rear engine RWD vehicle that was designed and built in the early to mid 1960's. It has more in common with a VW Bus than a V8 RWD A-Body GM.

That being said I would use what the manufacturer said to use in it for oil. VW called for GL-4 in their manual transaxles at least through the late 1980's.

http://www.youtube.com/watch?v=etlTPXcWoRg

[Desert_Eagle02]

Thanks guys. Lots of good info. So GL-5 MT-1 would be the correct oil? Good to know. I checked my Valvoline bottle and there is not MT-1 anywhere on it, so I'm still out of luck with that haha. But I will use it in the t-case and the diffs.

I did read on a few other forums when I was doing some research that people claim the have harder shifts using GL-5 in the SM465. They claim its too slippery for the sychros to work correctly. Others say they have used it with no problems. Seems like it can be a debatable topic haha.

[andyh1956]

Originally Posted by hatzie

The Corvair transmission was not a regular 4 speed Muncie transmission. It was a transaxle for an air cooled rear engine RWD vehicle that was designed and built in the early to mid 1960's. It has more in common with a VW Bus than a V8 RWD A-Body GM.

That being said I would use what the manufacturer said to use in it for oil. VW called for GL-4 in their manual transaxles at least through the late 1980's.

http://www.youtube.com/watch?v=etlTPXcWoRg

You are correct that the trans is in a "Transaxle" Configuration, but all the parts inside except for the mainshaft are "Regular Muncie 4 Speed Parts".
I have used the gears outta several of them before to repair the Muncies in my 55 & 57.
Corvair transaxles could be had for scrap price, while a "Scrap" Muncie was still expensive!

[hatzie]

They're worth a wee bit more now than they were in the 60's & 70's.
If the gears are cut the same direction as the 50's front engine transmissions then GM must've spun the Corvair engine "backwards". That's a piece of trivia I didn't know. I never had more than a passing acquaintance with the Corvair. In 1979 they were out of my price range and beginning to climb in value. I had four watercooled and one Air cooled VW along with a couple Datsuns and some GM and Chrysler station wagons and land yachts in the early 80s. None of them lasted long in the Northeastern salt.

[andyh1956]

One of my son's buds has a 66 Corvair w/ a v8 of some sort adapted to the transaxle & spun it around & now it's in the backseat! They race it on some kinda roadcourse racing where they set up the cones.
I asked him about the rotation of everything & he told me it has a marine starbord side camshaft that's cw rotation looking at the flywheel- I think I got that right- been a while since he told me that!
(I think I coulda found something ez-er to hot rod on myself, like a truck!)