Lubricants for 4 speeds

**David H.** · October 1, 2003, 10:48 PM

Re: Lubricants for 4 speeds

Tod; I build these trannys regularly enough to at least offer input. My experience with the muncie has led me to use a multi-grade gear oil like 85/120 so the old trannys will work good after they get hot, especiall the big-blocks with the large under car exhaust. A good example was a 68 BB car with only 33,000 miles on it and after it warmed up would not shift at all! I mean you could not move the shifter in any gear. We removed it from the car while it was still hot and after removing the side cover and shift forks I still could not move the sliders. After it cooled off it worked great even with the shifter installed. There was what seemed like an extra amount of clearance under the sliders (to the hubs), and I know these parts are suposedly matched at the factory, so my conclusion was that it was missed at QC. After putting in some penzoil 85/120 the tranny worked perfect at all times. Now maybe the old oil was bad or broken down but it looked clean and was the original oil. The only change that was made was the oil! This problem may have contributed to the low miliage of the car as while driveing for only 20 min. the tranny was starting to get progressively harder to get into gears.

I have used this oil on all of these "show" cars because they don't see alot of use and the frictional loss due to heavier oil is negate. I have been wanting to use redline oil or an additive in a muncie on the cars that drive alot so I hope others post about their experiences. regards; David

**Todd H 26112** · October 1, 2003, 10:58 PM

Re: Lubricants for 4 speeds

Thanks David, good input. I don't believe Pennzoil makes an 85W120. At least not currently. Did you possibly mean 85W140 GL5 or is this a discontinues oil?

**Duke W.** · October 2, 2003, 12:09 AM

Re: Lubricants for 4 speeds

I prefer the lubricant specified my my 1963 Corvette Shop manual - Mil-L-2105D.

Duke

**Gary S.** · October 2, 2003, 06:40 AM

Re: Lubricants for 4 speeds

Here comes the qualifier: I am only a shade tree mechanic but I use Mobil 1 synthetic gear lube with two containers of GM brand positraction additive to the differential and the same Mobil 1 with one bottle of posi additive for the transmission. I also use Mobil 1 gear lube in vehicles that sit outside all year long (obviously not a Corvette). Ever since I was in the Air Force in Alaska and had a Ford F-250 that would barely shift during the January cold, I have been using synthetic gear lubes. The only way to go imho.
Gary

**Richard D.** · October 2, 2003, 08:21 AM

Re: Lubricants for 4 speeds

I switched over to Mobil syn. in my trans (M-20) and noticed it shifted easier.

I am also going to use Mobil (or another syn. like Redline) for the rear when I get a chance to change it along with the GM additive. Some people have mentioned that when they changed over to synthetic, they did not even use the additive, and never had any problems, but I will use the additive when I do mine.

After switching over in the trans, I have not noticed any leaking. I mention that because although I did not have a leaking problem before, some people have mentioned that a changover to synthetics in motor or trans sometimes results in slight leaking through old gaskets.

Rich

**Todd H 26112** · October 2, 2003, 09:30 AM

Re: Lubricants for 4 speeds

How different is MiL-L-2105D from API's GL-5? I see them mentioned together.

**John M.** · October 2, 2003, 10:48 AM

Re: Lubricants for 4 speeds

Gary, I don't think its recommended to put the additive in the transmission. If you look at the Redline site you'll see they have a different formula for transmissions, which need a little friction for the synchros to work well.

**Dave McDufford** · October 2, 2003, 11:10 AM

Re: Lubricants for 4 speeds

Duke,

You lubricate your transmission with a Military Standard?

Sorry, I expect the engineer in you to be more precise.

Dave

**Duke W.** · October 2, 2003, 11:21 AM

Re: Lubricants for 4 speeds

80W-90 GL-5 is the same at the milspec. Apparently the commercial spec did not exist back in the early sixties for gear oil, so GM referenced the milspec.

If you go to www.api.org and search "gear oil" you will find a couple of downloadable PDF files - one on gear oil and one on motor oil. You'll get a good education on what they are about, how to differential them, and which one to use for your application.

Duke

http://eee.api.org

**Todd H 26112** · October 2, 2003, 11:29 AM

Re: Lubricants for 4 speeds

Thanks. Am already familiar w/ the GL specs from API but not the old MIL specs. The GL specs can I suppose be further broken down by the summary of ASTM tests.

Question: Since you seem familiar w/ the API information, why did GM spec GL5s for it's manual transmissions instead of GL4?

**Duke W.** · October 2, 2003, 11:53 AM

Re: Lubricants for 4 speeds

Don't know anything about the specific tests to qualify as a GL-5, but GL-5s are required for hypoid gears, which is why they are always specified for conventional axles. GL-4s are usually specified for tranmissions or transaxles that only have spur or helical gears. For example, my MR2 transaxle specifies a GL-4 because the final drive is a big helical pair - not hypoid - which is typical of transverse transaxles.

Given the above one would think that our four-speeds would require GL-4, but GM specifies GL-5 or the 2105 milspec, which is equivalent. I've never understood why this is the case.

Redline's technical information claims that GL-5s are "too slippery" for transmissions due to their use of EP additives to meet the GL-5 spec. Synchronizers need a certain level of friction to function properly. Also, Redline claims that the sulphur compound EP additives in GL-5s can be corrosive to brass at high temperatures.

Since I don't have the factilities or particular desire to do a long term durability test of GL-4 in my T-10, I stick with the original GM recommendation, which is satisfied by modern GL-5s, but just to be safe I use the GM 1052271 gear oil in both the axle and T-10 with the 1052358 additive in the axle, but NOT in the T-10.

Duke

**Todd H 26112** · October 2, 2003, 12:15 PM

Re: Lubricants for 4 speeds

Well then I'm not alone in not understanding their GL5 recomendation - many other automakers spec GL4 in the same viscosities in their manual trannies and I've never seen anything about a Muncie for example that makes it unique from other makes.

Some GL5s are purportedly better or easier on yellow metal alloys than others. However it's not part of the GL5 spec and there is no guarantee w/ a GL5 in a transmission using yellow metal alloys in their synchros.

I have a hard time finding specs or details on manufacturer labeled lubricants but I'm presuming the GM 1052271 gear oil is a GL5 90 or 80W90? I'm curious about the labeling if you care to fill me in here or email.

thanks,

**Duke W.** · October 2, 2003, 12:24 PM

Re: Lubricants for 4 speeds

I don't think the ...271 bottle label has anything about viscosity or GL- spec. I just take it on faith that its good for GM axles and our old four speeds. I also use it in the positraction axle (along with the additive) on my Cosworth
Vega and have never experienced any problems.

The CV B-W T-50 five-speed specifies ATF as do many modern manual transmissions.

Duke

**Clem Z.** · October 2, 2003, 12:36 PM

back in my drag racing days for better shifting

we used 30 weight 4 stroke motorcycle engine oil in our 4 speeds and the reason we used motorcycle oil is because it was to have some additive to prevent the gear teeth from "shearing" the oil molecules since 4 stroke motorcycle engine oil also lubes the trans. it seemed to work as we never had any lube related failures.

Lubricants for 4 speeds

Lubricants for 4 speeds

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