Manual gear oil.

[vw_bud]

Just wanted to check and see if full synthetic 75w-90 gear oil is a good oil to use in my gearbox, it's mild temp here in Georgia so I just wanted to check before I do it because it's all we have at the shop currently

[raygreenwood]

[Wildthings]

[shaggysboss]

Yeah, full synthetic 75w-90 gear oil should work fine for your gearbox, especially with the mild temps in Georgia. It's a good all-around oil and should perform well in most conditions.

[raygreenwood]

[SGKent]

the issue with many late fluids other than GL4 is that they are designed to work with different kinds of synchros. TheMotorOilGeek had a show discussing the importance of getting oils and transmission fluids right. Make sure it is GL4 because if it is too slippery like many GL5, then the transmission may never shift right again based on experiences some transmission builders here have had with clients making that mistake.

In one link below it reads re GL5, "Not for use in systems that contain yellow metal," meaning no brass syncho rings which is what out buses have.

Motor Oil Geek:

[vwmaniaman]

My 65 Bug and my wife's 87 Cabriolet had that typical cold snick when shifting from 1-2. My son recommended that I add some Lucas gear oil to it. I put in about a cup of it when near the end of filling. Drove it and the shift is smooth with no snick. I has stayed that way. It surprised me.
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75 Westy "Pumpkin Van"
86 Westy "Brown Betty"
87 Cabrio

[Wildthings]

[raygreenwood]

[Opossum]

What do you think of Driven STF Synchromesh fluid?

https://drivenracingoil.com/i-30497857-stf-synthetic-synchromesh-transmission-fluid.html
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[raygreenwood]

[Wildthings]

[telford dorr]

When I had my bus trans rebuilt by Transworks, I explained that it was doomed to live its life on the freeway turning 4K. They recommended running full synthetic 75W-140 oil in it, which has so far worked great. FWIW.
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[cdennisg]

[metahacker]

Swepco 201 or 203, depending on how you feel about moly (201 should shift better, 203 box might last longer with big loads)

if you plan to drive when it's quite cold, Swepco + Lubegard gear fluid supplement

Synthetic is not recommended

do not use Redline (in your gear box, their engine oil is very nice)

If you're obsessed with using synthetic, Motul 300V

If you're limping an old crappy gearbox along, GM p/n 88900399


Opinions vary greatly on this topic

Check the Vanagon forums for some very extensive discussion

EDIT: clarified re: moly

[vwmaniaman]

The Lucas that I used was gear oil and I can't recall if it was the 75-90 or the one to 140, but I imagine it was the 75-90. It listed safe for yellow metals on the jug. Beats me why it works so well but I am sure I only put in like a cup of it.
_________________
Working on a VW is like fun with a friend!
65 Beetle
75 Westy "Pumpkin Van"
86 Westy "Brown Betty"
87 Cabrio

[cdennisg]

[W1K1]

Swepco 210 is what was recommended from my rebuilder

https://swepcolube.com/wp-content/uploads/2024/07/SWEPCO-210-Multi-Grade-Gear-Lube.pdf
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1965 squareback 1500E
1971 bay window westy- subi swap

[raygreenwood]

Understanding I AM in the bus forum......the Haynes manual always suggested that the gear oil to use in the 411/412with manual transmission was Castrol Hypoy-C.

Now...Hypoy-C is GL-5. The problem is....and you see this in a lot of other forums where the yellow metal issue and GL-4 and GL-5 are being discussed.....you need to remember exactly what kind of car these other people are discussing.

The common comment is that GL-4 is for the "transmission"....meaning the gear sets with synchros....and GL-5 is for the final drive (and most specifically "hypoid" final drive).

Hint....you are dealing with people whose vehicles generally have a separate final drive.

We do not have that luxury. The final drive in a bus is in the same case and oil pool as the transmission section with its yellow metal synchros. It also does not have a "hypoid" final drive. There is nothing in the 002 or 091 that "requires" the slickness of GL-5.

To make matters worse on my 411's and 412's.....our transmissions DO have a hypoid final drive....which is why they suggested that a GL-5 should be used.

The difference in oils that state they "can" work in GL-4 and GL-5...is that yes, they have the friction mofifiers of GL-5 and SOME sulfur....but they also have LESS sulfur....maybe just enough...and they also have one of several buffer agents to prevent damage to the yellow metals by the sulfur.

The problem is how well is this documented?

Some of the better comments in forums actually suggest that if you have this same issue....yellow metal synchros AND a hypoid final drive in the same case....use what is suggested for SOME older Subaru because they have this set up as well. Not sure how true this is yet.

Ray

[airschooled]

Every VW bus manual clearly states hypoid oil is to be used in bus transaxles. The owners manual even puts hypoid in bold.

Robbie
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