Lubricants for 4 speeds

[Todd H 26112]

Re: back in my drag racing days for better shiftin

Interesting. I'd forgotten about motorcycles sharing their oil or for that matter straight weight oils. Do you have any more specific product info? Besides presumably meeting standard API gas motor oil standards - does it meet any special industry standards?

THis would be like using a straight SAE grade gear oil as far as viscosity goes. How does it shift in colder weather before it's warmed up?

Again, very creative approach!
thanks,

[Duke W.]

Re: back in my drag racing days for better shiftin

I think the "gears shear the oil" story is a myth. Involute gear tooth contact is a pure rolling motion. If there were any sliding contact they wouldn't last very long. Bearings are more likey to "shear" the oil than gear teeth.

My understanding is that oils blended for four-stroke motorcycle engines have more zinc-based anti-wear additive. So do API service categroy CI-4 diesel engine oils that I now recommend for vintage Corvettes.

I always used plain vanilla spark igntion engine oils in my three Honda motorcyles and never had any problems.

Duke

[Clem Z.]

Re: back in my drag racing days for better shiftin

we did it because in drag racing you do not get a chance to warm up the trans and cold gear oil made shifting hard and missed gears. we later used automatic trans fluid in the trans with no problems. the new 6 speed corvette trans uses dextron auto trans fluid so maybe we were just ahead of our times. i did not drive the cars,just built the engines but worked on all the problems that the drivers had. maybe duke or john with their engineering pbackgrounds could shed some light on this from a engineering standpoint. i am just a "lets try this and see how it works guy".

[Clem Z.]

duke all i know about the oil was what i read

motorcycle magazines and they said that was the reason not to use auto engine oil.come to think of it the oil pump does the same thing as the trans gears,right. what do i know they may have just wanted to sell the more expensive motorcycle shop oil.

[Todd H 26112]

Re: back in my drag racing days for better shiftin

I want to say there is 'some' sliding action in a spur gear albeit small compared to a hypoid gear. If so that could cause shearing at least in a multi-weight perhaps?

[Duke W.]

Re: back in my drag racing days for better shiftin

There is no sliding contact in gear teeth - including hypoid - if you have perfect involutes. Of course, there is some deviation due to manufacturing tolerance, but if there was any significant sliding contact the teeth would wear away very quickly.

Check any machine design textbook that has a chapter on gears.

Duke

[Todd H 26112]

Re: back in my drag racing days for better shiftin

In the old days I want to say SAE80(gear) was considered a 'winter' gear oil. Your SAE30(motor) oil is roughly equiv to an 80 to 85 weight. I don't think SAE80s or SAE90s are around anymore at least not in GL4.

Many modern manual transmission makers are using ATF or ATF-like lubricants these days - one school of thought is that these improves economy and I suppose it can be said that these transmissions are designed w/ this type of lubricant in mind from inception.

What I have heard among other things about ATFs in older tranmissions (like say a Muncie) is they can be prone to leaking but shifting may (or may not) be improved. This is why it's good to hear from others that have tried various things and what there experiences have been - thanks!

If you are feeling adventurous still - there is something out for GM and DC cars called Synchromesh. From what I can tell it appears to be a tad 'heavier' in viscosity than an ATF but lighter than a lightweight GL4 like Redlines 70W80 GL4. It's not spec'd to GL-4 but one could almost presume as much since it claims no other applicability besides certain modern manual transmissions. It too could be prone to leaking in an older tranny and I'm not advicing it's use here - just pointint out another potential possibility. I want to say I read somewhere that it does not contain the more aggressive additives commonly found in GL5s that can have a deleterious affect on yellow metals but can't find the reference off hand. Who knows..

[Todd H 26112]

Re: back in my drag racing days for better shiftin

Perhaps I'm mistaken but I was under the impression there was a very modest sliding action in involute gears due to velocity?

[Duke W.]

Re: back in my drag racing days for better shiftin

I'm not sure what you mean by "due to velocity" but properly designed mating involute gear teeth have pure rolling contact at any rotational speed. Manufacturing tolerance can cause slight deviations. Likewise, high loading can cause sufficient deflection to deviate from pure involute geometry, but if the gears are this highly loaded for long periods they will probably fail due to wear or fracture.

Duke

[Duke W.]

Re: back in my drag racing days for better shiftin

One thing to consider is that "SAE weights" of gear oils and motor oils are not the same. Most ATFs are 70W-75 gear oils and their actual viscosity is comparable to SAE 10W motor oil.

SAE 80W-90 gear oils have comparable viscosity to SAE 30 motor oil, and at about 100 degrees the actual viscosity of ATF is probably in the ballpark of a 80W-90 at 200F.

In a drag racing situation where the transmission never warms up, ATF in lieu of 80W-90 makes sense if the risk of blowing a tranmission is worth the potential benefit of better shifting.

Looks like it worked out okay!

Duke

[David H.]

Re: Lubricants for 4 speeds

Yes that is probably it as those numbers all run together after awhile! David

[David H.]

Reback to drag racing

Todd; As a machinist in the power industry I worked with a company out of Baton Rouge to put some special chemicaly applied coatings on some servo cylinders after we honed them to a desired finish. While he was visiting (and trying to sell our company on the product use) he had an example of some rear end gears coated with the product, he said they were top fuel funny car gears and they do not use "any" lubricant in the rear end or on the gears and only put some grease on the bearings in the rear end! Wow! he said the times were much improved for the car and he even produced some performance info from the crew cheif! I was very impressed and thought that was about the coolest thing going and that was in 89/90. I have no idea if this is still being done today? David

[Todd H 26112]

Re: Reback to drag racing

Interesting. Don't some top level motorsports teams qualify cars w/ say no gear oil? Sometimes rules have caused strategies like that to fall out of favor. That's just for a couple few laps but on race day back to regular lubrication.

[John H.]

Re: back in my drag racing days for better shiftin

The "Synchromesh" lube is actually Castrol "SynTorq" synthetic lube, re-packaged in GM and Mopar containers; it was developed jointly by Chrysler and Castrol as a replacement for the original ATF (Dexron II) that was specified for the T-56 tranny in the Viper. Due to the 90-degree V-10's uneven firing cycle, it set up harmonics at idle that caused "neutral gear rattle" with the car idling in neutral, which generated lots of customer complaints. The C5 also uses a version of the T-56 (although the Viper-specific unit uses bigger bearings and different metallurgy for the gears), so GM picked up the Chrysler/Castrol-developed lube and gave it their own name.

[John H.]

Re: Reback to drag racing

Nope - I can assure you that Top Fuel cars don't run a "dry" diff; I discussed this specific issue last month with one of the guys who builds Top Alcohol and Top Fuel cars when I was renewing my NHRA Dragster License, and he indicated that even with the highest-quality lubricants they can find, the 3.10:1 ring and pinion ($2,000 gearset) in a "Strange Engineering" or similar TA/TF diff is history after ten passes, and then they sell them to the spectators as souvenirs. I made ten passes in the car in the link below, and it had both a fill plug and a drain plug.

NASCAR teams frequently qualify with lighter-weight diff lube than they run in a race, but they don't run a "dry" diff either - wouldn't last a lap.