Synthetic 75-90 Versus 50W In The Deuce Transmission

[SasquatchSanta]

With winter threatening I'm flirting with changing to synthetics in the drive train. Considering the price of diesel fuel it's probably a good investment.

I've been reading through some old threads on lubrication.

Some posts say synthetic 75-90 is OK for everything --- the transmission, transfer case and differentials. (Cold climate environment).

Others say to use 50W in the transmission.

In a perfect world I'd like to stay with one lubricant for all the gear boxes. Is there a problem with running MT-1 (yellow metal compatible) 75-90* in the transmission?

I'm not quite as certain about running the higher priced synthetics in the engine. I'm running an oil pan heating pad so cold starts shouldn't be "quite" as much of a problem as they used to be.

My concern about the higher priced, higher mileage synthetic oil is that (IMHO) multis tend to suffer from fuel/oil dilution in the winter caused by cold weather idling. If you have to change oil because of diesel fuel contamination fears then are the synthetics really worth the added expense?

 

[gringeltaube]

A lot of opinions here: http://www.steelsoldiers.com/index.php?name=PNphpBB2&file=viewtopic&t=2858&highlight=tranny+lube

 

[jwaller]

I use the Mt1 75-90 mobil 1 in everything except the engine.

 

[OPCOM]

no problems after 6000 miles with 80-90 MT1 in the tranny and transfer.

 

[m-35tom]

you can run 30 in the trans and transfer in cold areas and 50 in warm, but you will still have to use hypoid 90 in the rears. i have 30 in mine now and the biggest problem is that it shifts easier.

 

[SasquatchSanta]

m-35tom sez:

you can run 30 in the trans and transfer in cold areas and 50 in warm, but you will still have to use hypoid 90 in the rears. i have 30 in mine now and the biggest problem is that it shifts easier.

I like the idea of running 30W in the transmission. I assume it would be good practice to change back to 50W in the summer even in Northern Minnesota? What say you?

PS: I don't want to detract you for too long from your work on the .71/.69 OD project . Keep me on your list.

 

[sprucemt]

Remember, the government already did the thinking on this subject. My opinion would be to stick with the military specifications. The specifications are for all weather usage.

 

[SasquatchSanta]

sprucemt wrote:

Remember, the government already did the thinking on this subject. My opinion would be to stick with the military specifications. The specifications are for all weather usage.

Yes ... you're 100% right.

My take on this subject though (IMHO) is that the government made those decisions over 40 years ago based on 1950s and 60s technology. Given that we are probably looking down the barrel of $4.00 + diesel fuel prices I can't help but believe that there are more modern products that reduce cold weather roll-over friction thereby giving better fuel economy. Given the sad state of my Power Wagon my Deuce may turn into a daily driver before spring therefore I'm out for all the fuel mileage tricks I can find.

I also plan on running cold weather before and after tests and posting the results

 

[emmado22]

I gotta agree with Spruce MT on this.. Uncle Sam has done LOTS of research on this stuff, and many times, when the MV Hobbyist does something to "improve" on Uncles thinking, it sometimes doesnt go so well. Someone on SS poured solvent into their tank thinking the multifuel could handle it.. He destroyed all the rubber parts in his fuel system. Syntheic oil historically doesnt go great in older engines due to the wear with the gaskets, and creates leaks.. WVO and other "made it myself" fuels really dont have the type of testing they need to see the long term effects on rubber components, lack of lube for the IP, ect... Even if you do save a MPG or so, at what point does the cost of the oil change pay for itself?

The TM says 80-90W for the axles, transfer, tranny, and winch. Engine can take 15W-30. 2 oils for the whole truck. Pretty easy.

I'll stick to what Uncle says.. If your trying to save a MPG here or there, the duece is the wrong vehicle to do it in. Moving 13,000# of metal is gonna take some fuel.

 

[sprucemt]

1960's, 70's, 80's and 90s, technoligies have changed the lubricant products. But the vehicles you are putting it in have not changed and still require a specific specification. Other than a few very minor changes the government still uses what was originally spec'd for the vehicle. Your vehicle, your choice. I am just a believer in keeping it simple and understand that the government has spent millions of dollars already figuring it out. In the case of vehicle maintenence, incredibily well.

 

[Bill W]

Hey Guys remember that the military likes to standardize ( the reason behind M-series ) and for the sake of supply/inventory will use one oil that work on all the mil vehicles., So what might be a perfect oil (ie 90w) for a M-37 tranny will only be marginal in a M-35 but still acceptable, heck look at GAA ( Grease,Automotive AND artillery ) thats a do all product. Heck all mil trucks use to use 30w, now the same vehicles take 15-40., As mentioned technology has improved in the past 40+years

 

[OPCOM]

Today I was lazy and took the M35 to the diesel shop to have the chassis lube and transmission, transfer, and differentials serviced.

I was offered 50W synthetic GL-5/MT-1 for the transmission and transfer, but I stuck with what I have been using, the 80-90W GL-5/MT-1. I declined because I ws not sure the thinner oil would do as good a job keeping the oil film.

The move to thinner oil over time looks like a ecology/green-pushed initiative. Therefore it may not have the best interests of the existing fleet in mind but rather focuses on fuel economy and expects the automotive industry to keep up.

I realize the TM calls for GL-1, but I have found it to be very thin at high temperatures and the transmission seems to be a bit harsher and noisier when hot, as if it is not being lubricated.

For the lube job I brought my own non-synthetic 80-90W MT-1 rated GL-5. It lasts a long time before "losing it" due to heat, and the deuce transmission does get very warm. Sometimes it is downright hot, like after a highway run.

GL-5 is an evolution of lube that is better in many ways than the original GL-1. GL-1 itself does not seem to have the chemicals in it that attack the M35 transmission and transfers and so would be inherently MT-1. I believe important thing is to always make sure the lube is rated for MT-1 service, meaning it is compatible with yellow metals found in the M35 transmission and transfer.

The axles got 80-140 non synthetic gear oil. MT-1 is not required for the differentials.

So, right at 20K miles to date on 80-90 MT-1 rated GL-5 and no problems. The transmission does not make any more or louder noises than it ever has, and everything seems fine, works smoothly.

 

[thehaas]

castrolo syngear 50 meets m1 does not corrode brass parts perfect viscosity tryed 75 90 shifted to hard also added one quart lucus pure synthetic also use in tranfer case way slippery oil notice quieter on road less heat