Non-synchro GL-5 gear oil for a Muncie

[Duke W.]

Re: Non-synchro GL-5 gear oil for a Muncie

As you stated, I also don't understand why the Valvoline product would be labeled for non-synchromesh transmissions. Maybe they bought into the yellow metal corrosion myth. In any event, you summarized the GM recommendation - Mil-L-2105 followed by the commercial equivalent, which is GL-5. The mil-spec was canceled over a decade ago and replaced by GL-5.

So the equivalent of current GL-5 has been specified for C1-C3 manual transmissions and axles for at least 60 years. I have never seen nor heard of actual observed brass synchronizer corrosion in an automotive manual transmission. It can occur, but only at temperatures well above typical operating temperatures.

So, again, I go by the old adage "if it works don't fix it" and continue to recommend SAE 80W-90 GL-5 for vintage manual transmissions and axles. Of course each owner can choose whatever lubricant he deems appropriate regardless of what GM recommended. Everyone is free to experiment with their own car.

I might add that beginning around the mid-1970s new design transmissions typically specified lighter lubricants. For example, the BW T-50 five-speed in my Cosworth Vega recommendation is ATF, which is basically a 70W-75 GL-4. The recommendation for my '88 MBZ 190E 2.6 is ATF or non-detergent SAE 20-20W. For my '91 MR2 the recommendation is SAE 75W-90 GL-4. The final drive gear set in a sidewinder transaxle is a big helical set, to they don't need GL-5, which is necessary for hypoid gear sets.

Perhaps Valvoline did not look back beyond the seventies. Most manual transmissions from that period to today do not specify GL-5. One must remember that modern automotive lubricants are formulated for "modern" cars - say no more than 20-30 years old.

Maybe someone with a modern Corvette can look at their owner's or service manual and tell us what the lubricant spec is for the manual transmission and axle. Modern Corvettes are known to have "transaxles", but that's a misnomer. The transmission and axle are bolted directly to each other, but are sealed relative to each other and have separate lubricant supplies. My guess is that the trans is GL-4 and the axle, which has a hypoid gear set is GL-5.

Duke

[Robert G.]

Re: Non-synchro GL-5 gear oil for a Muncie

Here's Valvoline's product information sheet about the high performance gear oil:

http://content.valvoline.com/pdf/high_performance_gear.pdf

and for synchronized manual transmissions they say to use Professional Series Manual Transmision Fluid or Synchromesh Manual Transmission Fluid

http://content.valvoline.com/pdf/vps_manual_transmission_fluid.pdf

[Mark E.]

Re: Non-synchro GL-5 gear oil for a Muncie

Here's Valvoline's product information sheet about the high performance gear oil:

http://content.valvoline.com/pdf/high_performance_gear.pdf

and for synchronized manual transmissions they say to use Professional Series Manual Transmission Fluid or Synchromesh Manual Transmission Fluid

http://content.valvoline.com/pdf/vps...sion_fluid.pdf

According to the second link, this manual tranny fluid is GL-4, not GL-5... so we're saying we shouldn't use it for our Muncies?

[Duke W.]

Re: Non-synchro GL-5 gear oil for a Muncie

Do you really think Valvoline took into account the requirements of transmissions designed 50-80 years ago? The original GM spec is Mil-L-2105, which was later superseded by SAE 80W-90 GL-5 that you can still buy, today, including the Valvoline brand.

Like S-category engine oil, which is formulated for modern catalyst equipped engines with "roller everything" valve trains, not vintage engines with sliding surface valve trains, VPS is formulated for MODERN manual transmissions designed in the last 40 years that have a lighter viscosity lubrication requirement.

The VPS data sheet does not even specify the SAE viscosity range. Maybe it's only a 70W-75 like ATF. Would you put ATF in your vintage manual transmission?

As I said, if you want to do a research project with your vintage BW or Muncie transmission, be my guest and let us know the results after you accumulate a few million miles of testing.

It's really time to put this one to bed and let everyone use the data and facts presented and make their own decision.

Duke

[Joe L.]

Re: Non-synchro GL-5 gear oil for a Muncie

Here's Valvoline's product information sheet about the high performance gear oil:

http://content.valvoline.com/pdf/high_performance_gear.pdf

and for synchronized manual transmissions they say to use Professional Series Manual Transmision Fluid or Synchromesh Manual Transmission Fluid

http://content.valvoline.com/pdf/vps...sion_fluid.pdf

Robert------


I think a lot of the confusion here is caused by the use of the term "synchromesh". The fact of the matter is that virtually all manual transmissions have been "synchromesh" for years. So, if the Valvoline Synchromesh Manual Transmission Fluid is indeed applicable to all "synchromesh" manual transmissions, then that would mean that it's applicable to virtually manual transmission made for the last 50+ years. I don't think so. I think the term "synchromesh" used in the context of transmission fluid applicability has some other meaning, although I do not know what it is.

You will note that the Valvoline Synchromesh Manual Transmission fluid spec sheet mentions that it is suitable for applications using GM #1052931, GM #12345349, and GM #12345577 (which is now GM #8890033). All of these were/are SPECIALTY transmission lubricants. For example, the 1052931 is a 5W-30 fluid used for, among other applications, the 1989-96 Corvette ZF 6 speed transmission. The 12345349, 12345577, and 8890033 do not specify a GL-rating nor do they specify a viscosity rating.

The fact of the matter is that for all 63-74 Muncie applications GM specified an 80W or 80W-90 lubricant meeting spec. Mil-L-2105B as Duke mentions. That spec is superceded by spec GL-5. So, I fail to understand why there is any confusion and endless discussion here regarding what is the correct specification lubricant to use for a 63-74 Muncie.