My observations with 50wt in tranny

[moriboy]

While my truck was down with an IP problem, I had some time to do some PM work. One being a tranny service.

After many hours of reading SS threads on this highly debated subject, I decided to change out the 90wt gear oil, and put 50wt motor oil back in.

Note, my test drive last night was only 50 miles, but here is what I noticed:

While shifting both up and down, it seemed like the trans "snapped" into gear a little easier. Last time I drove her, I noticed that in particular the jump from 3rd-4th sometimes took a little more effort than the other changes. I did not notice this last night. Finding 4th just seemed easier.

Now could this just be my imagination? Sure! Is 50 miles enough to really enough to make any real conclusions? No! But, my opinion is that maybe some of the EP addiditives in gear oil might slightly hinder the function of the syncros.....

 

[Bob H]

90wt gear oil and 50wt motor oil have virtually identical viscosities.

 

[Beerslayer]

I noticed that my deuce transmission runs pretty hot, so for that reason I have kept the 90w in there.

Have you checked to see what temperature you are running?

 

[moriboy]

True, viscosity is about the same but they have different additive/friction packages.

I don't have any temp info.

 

[rosco]

Transmissions/rear ends will often run hot, like several hundred degrees. That is normal when the work.

Your right Moriboy. Lots of the old iron, doesn't get along with the EP additives, especially the transmissions. They call for straight mineral lub, WO the EP. One place this shows up, in transmissions, is between the gear changes, where helicale gears are used. Under loads, the helicle cut gearing causing side thrust. That can help cause them to jump out of gear, one way or the other. As in accelleration, or de-accelleration. Usually, along with wear, the EP stuff is too slippery, the detents can't hold the gear changes in place, and it comes out of gear, under loads!

So under one load, the normal thrust might pop the tranny out, but under opposit loads, it can pull it into gear. The gearing is cut different in different trannys, so its hard to say how each reacts, in each gear.

 

[Katahdin]

I'm not the most experienced gear finder by any stretch of the imagination, but on one approach to my driveway I'm going up a hill and I have to downshift from 4th-to-3rd-to-2nd. I'm using an All Mineral GL-1 Ford Tractor Transmission Oil from Tractor Supply and haven't missed or come out of gear yet.

 

[Marlboro]

on the type of oil i use...

 

[deathrowdave]

Correct 90w gear oil 50w lube oil are the same viscosity . Should not make any difference in resistance in gears and internal trans parts

 

[M543A2]

As an alternate oil we use the transdraulic oil recommended for farm tractors. It helps shifting in really cold weather. You have to watch that your seals are in good shape or it can get away faster than gear oil. We have a 5 ton that was balky about kicking in the front drive. We put transdraulic in the transfer case and the problem is now much better. We used it in an M715 Jeep that with gear oil would not hardly move at first in cold weather. It was no problem with the transdraulic oil in all of the cases. We figure that this oil holds up under high horsepower loading in gear cases in farm tractors that get hot and run for hours at a time, so the truck application is not a problem. So far this has proven to be true.
Regards Marti

 

[M543A2]

I firmly believe that if a transmission is popping out of gear with any oil there is wear or incorrect clearances in it causing the problem, not EP oil.
Regards Marti

 

[Clay James]

I put 50 weight in both my trucks and it made a huge difference on both. I also put in some Lucas so that may have helped some. Before it would be tough to get into gear sometimes, and 2nd was particulary hard. One time at a light I got stuck trying to get it into 1st and just couldn't do it so I had to start in 2nd. With the 50 weight I rarely have trouble anymore. Sometimes 4th on my 109 will grind a little going into gear if I shift it too fast trying to deal with the 3rd to 4th gap.

 

[MyothersanM1]

Running 50wt Rotella HD engine oil in the 818 now. I made the move after reading many discussions here and other sites regarding this same issue. I have driven little since, but it is feeling a little smoother.

 

[moriboy]

I'm convinced I made the right choice. I drove my truck to work yesterday and today, and the transmission felt so good.

 

[plym49]

It's true that there is not much difference in terms of viscosity.

I was taught that the difference is in the additives. Gear oil additives are optimized for heavy point contact. Motor oil is optimized for sliding friction with the load spread over a large area.

The first question is what matters. Transmissions spend a tiny amount of time shifting; the majority of the time they are, well, transmitting power. So should you optimize the transmission lube for shifting, or for power transfer?

Some manual transmissions are designed to use lubricants like ATF. OK, if that is what they are designed for, no problem. Our Deuce transmissions specify gear oil.

So the question then becomes whether modern motor oils are so 'good' that any shortcoming traditional motor oils had in terms of handling high point loads is overcome by modern additives. Maybe our transmissions specify gear oil because that is all they had. Maybe. But they still specified a lubricant that can handle high point loads.

As far as I know, no one has ever factually answered that question. We'd probably need a lubrication engineer and a powertrain engineer to weigh in.

Until that happens, or perhaps until someone can convince me otherwise, I will use gear oil in my transmissions. I don;t care if the effort to shift is a bit higher. Double clutch. It''s a Deuce, not a buttery-soft Lexus.

A question for those who put motor oil in their transmissions: do you also put motor oil in your third members? If not, why not?

I again state that the above is based on what I was taught supplemented by logical thought. I welcome factual information that can help explain this on a engineering basis.

 

[Flyingvan911]

I have GL-5 in my deuce (for 1 year and 2,000 miles) and haven't had an issue. Not to restart the civil war of lubes, but, I think an expert opinion would really help. There are so many questions and info that would be good to know.

 

[mobileauto2000]

There is a friction modifier in gl5 that can make the syncos not work well.
If your transmission shifts fine with it great. If yours was like mine and almost imposable to get into second and tough in 3 and 4 gear without double clutching switch to motor oil. You will notice a improvement right away and it will get even better with time as the friction modifier from the gl5 wears off.

There is another line of thought that the friction modifier cause the needle bearings in the second gear set to fail at high speeds. This is beyond my expertise weather its true or not.

There also was another thread on this where someone posted the Rockwell specs and they wanted motor oil not gl5

 

[Katahdin]

I looked up some gear lube viscosities and was surprised at what I found. Maybe some SAE90s are thicker than others explaining why 50 weight motor oil seems easier to shift?

Napa GL-1 seems off the chart but its the spec listed here.

 

[mobileauto2000]

Syncro's are basically clutches that slow down or speed up a gear to make it mate with the other. The friction modifier can reduce the efficiency of the syncro and make it hard to shift. It is not the viscosity that causes the problem it's the friction modifier.
Also not all transmissions are effected by it.

 

[jasonjc]

There is a friction modifier in gl5 that can make the syncos not work well.
If your transmission shifts fine with it great. If yours was like mine and almost imposable to get into second and tough in 3 and 4 gear without double clutching switch to motor oil. You will notice a improvement right away and it will get even better with time as the friction modifier from the gl5 wears off.

There is another line of thought that the friction modifier cause the needle bearings in the second gear set to fail at high speeds. This is beyond my expertise weather its true or not.

There also was another thread on this where someone posted the Rockwell specs and they wanted motor oil not gl5

The syncos are between 2&3 and 4&5. There is not one for 1st. That is why it's harder to get into 2nd. As for the oil or lube. I'm so confussed

 

[glcaines]

I use GL-1 straight mineral oil and have zero issues with my transmission. Plus, GL-1 is yellow-metal compatible, and it is low-cost.