1962 T10 Transmission Oil

[Christopher R.]

Changing the oil in my '62 with a T10 transmission. Last time, I used Pennzoil GL-5 stuff. I don't think it worked well. But maybe that wasn't the oil's fault. I had some left over from the last time which was around 20 years ago. So I started with that. But it's not enough. Now I can't find that old oil. So I thought I'd just buy some other GL-5 80W-90 oil. There's plenty of that. But they all say that it's for limited slip differentials.

Pennzoil does make a "Synchromesh Transmission Fluid." See: https://www.pennzoil.com/en_us/produ...ion-fluid.html

Looks like a good product. But it doesn't say whether it's GL-4 or GL-5. Doesn't say what the viscosity is.

Any comments? I need to buy more oil to fill the transmission. I don't know if I should buy generic GL-5 oil. or the Pennzoil Synchromesh oil.

[Harry S.]

Re: 1962 T10 Transmission Oil

Chris, this is what I use in my 63 T10...


IMG_1083 (1).JPG

[Duke W.]

Re: 1962 T10 Transmission Oil

If you look at contemporaneous literature like owner's manuals, service manuals, and AMA specs you will find that the specified oil for BOTH manual transmissions and hypoid gear axles is Mil-L-2105D. Back in the day we just called it "gear oil".Mil-L-2105D was replaced in the seventies by the API spec SAE 80W-90 GL-5, and the mil spec was eventually cancelled and the military uses the API spec. GL-5 has an EP additive that is necessary for the highly loaded hypoid gears in the axle.Modern manual transmission/transaxle designs that DON'T have a hypoid gear set use lighter oil like SAE 20-20W non detergent engine oil, ATF, or some other name that may of may not involve an API spec. If and API spec is specified it is usually GL-4, which lacks the EP additive for hypoid gear axles.There is a myth that GL-5 causes "yellow metal corrosion", but that can only occur at temperatures well above the operating temperature of the transmission. I have never seen nor heard of observed corrosion in an old transmission and that includes guys who have overhauled hundreds of them.Many vintage Corvette owners are using GL-4, but I have never heard a rational basis for deviating from the original spec, nor have I ever seen any durability test data for GL-4 in a vintage transmission.Just because a gear oil says "suitable for limiting slip differentials" DOES NOT mean that it actually has the additive. Most don't, so you have to add it when using GL-5 in a clutch type LSD. Do no use the additive with GL-5 in a transmission.SAE 80W-90 GL-5 is a generic product, and you should find a selection at any FLAPS, both national brands, and brands you may not have heard of.Duke

[Duke W.]

Re: 1962 T10 Transmission Oil

Sorry about my above post. All my paragraph spacings were eliminated including trying to edit them back in. Sometimes this happens. I have no idea why.Duke