What Types Of Gear Oil Used In 1967 Cj-5?

Oh jeez. You are right Pete. I made a mistake. The wheels will turn the opposite direction if an open differential and the driveshaft is locked. If the driveshaft is locked and it's a LSD or locker, the wheels won't turn at all. They will turn the same direction if the driveshaft can turn.

 

It appears that 80w90 GL-5 destroys the synchros by peeling off metal from what I've been reading. That begs the question. What is different about manual transmissions in newer cars that can use GL-5 that allows them to use Gl-5 without having their synchros wrecked??

 

My transmission & transfer case leak and so I don't want to put expensive gear oil in them. In about a year, I'll have the time to re-seal them and at that time I'll probably use the expensive gl-4 stuff.

In the interim, I'm going to either add low cost motor oil or else gl-1 gear oil because they are both reasonably priced.

Does anyone have any idea if 10w40 motor oil would be better or worse than 80w90 gl-1 to use?

 

By the gallon, Staylube GL-4 is six bucks a quart.
How much are you really going to save by going to an inferior grade - compared to the cost of the components involved?

 

My Jeep leaks a lot. For all I know, it could leak gallons per year.

And the reasonably priced 80w90 GL-1 oil I have is really thick and gooey and looks like it would leak out slowly. I'm leaning towards putting that in rather than 15w40 motor oil unless someone here knows something that makes it look like 15w40 would be better than 80w90 GL-1.

 

Amazon has it for $26.05 a gal.

 

Check out tractor supply if you have one close by. I changed the oil in my ax-5 yesterday with some GL-1 from there.
Traveller Ford Tractor All Mineral 90 Transmission Fluid, 2 gal. - For Life Out Here

 

DO NOT USE MOTOR OIL IN YOUR MANUAL TRANSMISSION UNLESS IT CALLS FOR IT. And very few do.
I'm not trying to be mean here but this sounds like a case of trying to save pennies now in order to spend dollars, lots of dollars, down the road. Hard parts like gears and shafts for the T-86 can be expensive and hard to find. Not to mention GOOD parts are getting harder to find for the 18 transfer case. If the Jeep leaks so bad that you are afraid to spend a few bucks on the proper gear oil perhaps it should not be driven until it can be repaired. Using the wrong lubricant can destroy these components.
GL-5 is fine in the differentials. If you have a limited slip, then use the friction modifier as required. GL-4 only in the transmission unless you live in a very, very cold climate, then a lighter oil can be used, but follow the recommendations. In the transfer case I'd use the GL-4 as some migration of oil can happen between the transfer case and transmission on these, although the transfer case by itself can handle GL-5 fine.

Later model transmissions are made from different materials and processes. That's why later model units call for or can handle different lubricants than older vehicles and components.

 

Someone on the Net who is known for being a specialist in oils told me not to use GL-1 80w90 gear oil but that a Diesel 20w50 would give gl-4 protection. I still have some emails going with him to find out if it is mandatory that the bottle of 20w50 oil actually state that it is at GL-4 protection or not. I found 20w50 at Walmart for only about $11 for a 5 quart bottle. I'll keep gathering information on potential alternatives to the high priced oil.

So far, I haven't added any oil to my transfer case or transmission and haven't driven my Jeep at all and I'm going to keep gathering information before deciding what to do.

Whenever I finally do add oil, I'm going to check the levels frequently so I can keep better track of the rate the oil leaks out of my transmission.

If anyone knows of any tests done on gear oils by an independent organization, please let me know. In particular, independent tests that tell what the various levels of GL protection (GL-1, ....,GL-4, GL-5) actually do in practice, if anything.

Oil companies have been caught making bogus claims for their higher priced gasolines numerous times by independent testing organizations.

One tester I found on the Net also caught them making bogus claims for many of their motor oils, but unfortunately he never tested gear oils.

When Jeeps like mine are properly re-sealed, do they leak as little as typical new cars or do they have some sort of problems where they will still leak a lot?

 

Good rehab can definitely reduce fluid losses, if attention to detail is given.

BUT - No sixty year old engineering is going to be as leak-free as modern cars. (Although I also doubt any modern design will be around in sixty years from now.) These older vehicles were intended to be actively maintained, possibly into perpetuity. Modern equipment is meant to be "service free," but has a finite lifetime.

I prefer the older philosophy. In that light, a few quarts of oil is part of the price of owning and enjoying a classic, and should be accepted as such.

To answer your question, there are hundreds of sources, if not thousands, to google regarding the technical difference of GL-4 and GL-5, and many cite scientific studies. Many net forums have addressed it numerous times, including here on EarlyCJ5

I don't understand why you are so determined to NOT use the right oil, the one which has been proven effective over many decades. You are willing to trust 'some guy on the net' but not the engineers who won WWII?

It seems like there are a lot of unknown risks and wasted energy in trying to re-invent the wheel, IMHO.

 

Just to follow up on this, you seem determined to follow other counsel than what's given on this forum. You asked, and advice was given. See Nick's response (a credentialed and very experienced expert) above. I'm done.

Regarding leaks, if you search old posts there has been plenty of discussion of leak sealing for these Jeeps. However, getting to zero leakage over infinite time is probably impossible. Can you get to the point where you don't need to top up the fluids every month? Sure. Can you seal it so the Jeep never marks your driveway? Unlikely.

 

I read somewhere that motor oil would give similar protection as gear oil in transmissions. Delvac or similar. Even if this is true, why would you do it unless you had an emergency of some sort? Its not really cheaper and even if it was, water is free, but you wouldn't use that, right?

I have seen what GL5 does to synchronizers. It creates an oxide that rips parts of the synchronizer off. Feel free to use whatever you want, but GL4 does not do that. Thats what i use because as much as I don't mind rebuilding transmissions, I would rather not.

Just because something else might work adequately, if the proper thing is available, why not use it? I understand the specs that some companies and individuals claim their product to be able to pass. I read those articles too. I decided it was prudent to just not experiment with my own stuff.

Post your experience. Maybe we are all wrong. Fix your leaks and rebuild your gear boxes. After all that effort you might want to use the tried and true.

 

I am not determined to not follow the advice here to use 80w90 gl-4. I believe you: I'm already convinced that oil would work fine. I'm simply going to leave no stone unturned to see if I can find anything else that is not so overpriced that would also work fine. If I can't, then I'll use the overpriced stuff.

I don't yet know the rate of the oil leaks in my jeep and if they are large enough, the expense of using 80w90 gl-4 could be huge.

I've been convinced that GL-5 spec oil will ruin my synchros, so that is definitely ruled out.

I'm not going to drive my Jeep until I have oils in it that I trust and if the expense of keeping up fluid levels with those oils becomes too large due to leaks, then I'll stop driving my Jeep until I have the time to work on it and stop the leaks or at least reduce them down to manageable levels.

If I find lower cost oil that seems to me to be ok (and I don't convince easily), I'll post here what I found, exactly why I think the oil is ok to use, and get your opinions.

I did the tests recommended here and found that my rear differential is limited slip but the front differential is not.

I wonder why one is and the other isn't? Wouldn't I get a lot more traction in snow if both differentials were limited slip? It almost seems like a contradiction to have opposite types of differentials being used.

 

Limited slip differential in the front comes with steering and handling issues. This equates to increased liability and the characteristics lead to increased wear and tear factors from the factory/dealer perspective so is an uncommon option.
Common perception also follows that climbing a hill or obstacle weight transfers to the rear so more traction is needed. Also these vehicles are very light in the rear so common for more traction needed in the rear than the front which has more weight bias due to the engine weight.
Something you might want to keep in mind is these are NOT modern vehicles, they were sold during a time when they were utility vehicles commonly used on farms, off road as work vehicles, and modified for specific tasks. Less commonly used as recreational vehicles like commonly used today. As such they have different requirements than modern vehicles for maintenance, repairs, drivability, etc.

 

Sigh, you keep saying overpriced on GL-4. If that is your perception, then try pricing out modern synthetic gear oils. NV-4500 5 speed requires much more expensive oil for which there is no substitute and it requires much more in quantity.
If this one thing makes you balk about using an appropriate oil for the health of your vehicle then perhaps an early CJ may not be the best vehicle for you.

 

You definitely "don't convince easily." But you are ignoring the results of your own research - you have conducted an inquiry among the experts here, and already have gotten unanimously consistent responses from some of the most experienced Jeep people in the world. Do the math.

This 'cheap oil' thing reminds me of the farmer who was trying to cut costs by teaching his pig to eat sawdust.
He says," Dang, that was frustrating. I spent six weeks getting him to eat the stuff, and then just when he does… he dies."

 

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