Best gear oil in 2.5 ton axle

bebyb

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Hello everyone. Since the weather is nice I figured it would be a good time for a gear oil change. I know somewhere in the TMs it says to use 80w90. However, would 85w140 conventional or 75w140 synthetic be better? I figured the thicker oil might protect better than 80w90 but if I need to stick with 80w90 I will. Either way, I know if it ain't broke, don't fix it and I don't want to have to be replacing axles for ANY reason. Thank you so much!
 

Scar59

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Stick w/ the 80/90 called out in the lube orders. Auto Zone has a good price on 5 gallon pails, Get the hand pump that fits the pail bung. Pump away on level ground.
 

Karl kostman

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Stay away from anything synthetic in your truck or it will become a "LEAKER" I have run 80/90 in every truck I own and have owned, its done well in every application!
 

dmetalmiki

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I hope that is not "to the top of the axle!" (case).
It is 'good when you can just touch the oil level through the level plug with a crooked finger.
Just 'dripping out' is fine also, that is how I have them, and with 'Molyslip' added. (In every thing!).
 

cattlerepairman

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I remember reading here, a long time ago, about things to do to make axle seal leaks less likely to occur. One piece of advice was to ensure that the pumpkin does not get overfilled (see "crooked finger" advice above; do not fill higher than that) and to use 85w140 conventional gear oil because the slightly thicker viscosity makes it less likely to seep out. I have no experience using 85w140 conventional, so I cannot say whether or not it truly makes a difference. Others thought it did.
 

41cl8m5

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Ok guys, l have been doing a lot of research on the Rockwell axles on these trucks and yes the correct full level from the US Army "HeadShead" as it was called is 1/2" below the fill plug on level ground. Above that and the oil can go past the seal on the end of the axle and will mix and "wash out" the axle wheel grease and causing slinging wet look on the rim and if not fixed also coating the brake shoes inside the drum making it very hard to stop! One other thing, also check the breather on the axle the top of it is springy, it lets pressure build up out with out letting other stuff like water, mud in. So the cap of the breather needs to be able to twist and push down and spring back up on its own, if not it is faulty and needs cleaning or replacing.
Now the reason for 1/2" below the fill plug is, as the oil gets warm under normal operating conditions it will expand and rise in level. The military was having a lot of issues with leaking seals and after inspecting them most were still good. It was only after a test run of vehicles that were ordered to have the lower level of oil this way for a year they were then checked again with none of those trucks having had any gigs throughout the year, that is when the order came out for the change for all trucks with that type of axles.
Now as for some of us using the finger thing would be either difficult or unpalatable, you can make a dip stick. Take a piece of metal tubing or steel rod that you can bend 90 degrees and mark it somehow 1/2" below the bottom of the horizontal part and the tube only needs to be another 1/2" long after that as far as th horizontal part you can loop make it bigger than the fill plug hole, so you can't accidentally drop it inside.
Sorry about the length of the post.
 

rustystud

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I run 85w 140 conventional. :driver::driver:
For a hot environment 85W-140 is a good oil to use. Further North like Michigan you should use a 85W-90 weight especially in winter. Here in the Pacific Northwest since it normally doesn't get as cold as Michigan I can use a 85W-90 to 85W-140 weight . It all depends on price for me here.
Just remember the double reduction differentials will run hotter then a standard differential.
 

winfred

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i notice my diffs sing above 50 drive and coast with the 80/90 tractor supply lube i installed at service time, i did 395s and reman airshift t-case at same time but have heard the same singing in videos posted here so think im gonna consider that as a flush and step up to 85/140
 

gringeltaube

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For a hot environment 85W-140 is a good oil to use................ double reduction differentials will run hotter then a standard differential.
In such hot environment, wouldn't a 140wt oil make it even worse, compared to 90wt?

From the early 70's up to the newest book I could find (LO 9-2320-386-12 from JAN 96), they all call for GO 80/90. No mention of 140wt oil, anywhere.
 

41cl8m5

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That LO you are referring to is 22 years old. The military was only concerned with mission ready not longevity thinking. They had a big supply, support and maintenance command to fix the broke things usually looking like it did not cost much to the trucks operator point of view also. Now don't quote me on this but was 85w-140wt available 22 years ago? I don't think it was. It is now anyway.
Rusty' statement in the post above come from years of hands on work with big equipment like the Deuce and I for one consider him very talented and one of a few experts on this forum.
 

Floridianson

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Ok guys, l have been doing a lot of research on the Rockwell axles on these trucks and yes the correct full level from the US Army "HeadShead" as it was called is 1/2" below the fill plug on level ground. Above that and the oil can go past the seal on the end of the axle and will mix and "wash out" the axle wheel grease and causing slinging wet look on the rim and if not fixed also coating the brake shoes inside the drum making it very hard to stop!
.
Do believe if the grease slinger plate holes are kept clean then any oil/grease mix comes out on the outside of the drum. A leaking wheel cylinder is what gets the inside of the drum/shoes wet.
As far as the gear lube getting past the outer seal from what I have found it is because someone did not install the cork/sealant in the key way. Also someone not keeping the correct preload on the nut that holds on the outer seal. Gimpyrobb and myself did a leaking outer seal at the Ga. rally and the operator said he just had the axles done by a mechanic shop. Well before I removed the inner nut I ran it one complete turn in. The TM's call for 1/4 back off from 50 foot pounds but this one was one turn. That is what caused his outer seal to leak. We have talked about this and myself I go to preload and only back off 1/8 turn. Also taking care of the key way.
Research is good but sometimes you have to get your hands dirty to find the problem.
 
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Kaiser67M715

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In such hot environment, wouldn't a 140wt oil make it even worse, compared to 90wt?

From the early 70's up to the newest book I could find (LO 9-2320-386-12 from JAN 96), they all call for GO 80/90. No mention of 140wt oil, anywhere.
While I'm no expert, I know several vehicles that call for a heavier weight differential oil when towing. Towing creates extra heat, and I think to keep the same properties of a 90wt at a certain temp, they use a 140wt.

I'm having a little trouble trying to write in words what I'm thinking, but essentially the 140 would work the same a 90wt only at a higher temperature.

Sent from my SM-S920L using Tapatalk
 

41cl8m5

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Getting the hands dirty has been my life. But understanding how things work and why to me makes me more than just an average mechanic or grease monkey. This is some of what I have been looking at:
PS Magazine 393 Pages 42, 43:
Axle Lube  2.5 ton.jpg
And Floridianson this I believe is your addition about the cork which is an excellent point:
PS Magazine 363 Pages 8, 9:
Cork 2.5 Ton Axle.jpg

I have been doing a restoration with mods to My M35A2 (1968) that started life as a M35A1. I won't get into details on my truck, that's not what that topic is about. But because life keeps getting in the way my project has been on and off again for 4 years now.
 

rustystud

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In such hot environment, wouldn't a 140wt oil make it even worse, compared to 90wt?

From the early 70's up to the newest book I could find (LO 9-2320-386-12 from JAN 96), they all call for GO 80/90. No mention of 140wt oil, anywhere.
Like "41cl8m5" mentioned, there was no easy way to get 140W gear oil back then. I know as that was when I was only working on gears. All day long, everyday. After a few years of nothing but gear work I got pretty sick of them for a while.
As far as the weight of oil in cold or hot environments, it is pretty simple. Just imagine pouring oil at 20F . The lighter the oil weight, the easier it will pour. Heavy weight oil will turn to thick sludge at that temperature. Now it's just the opposite in summer. At a 100F temperature that light weight oil will pour like water, while the heavy weight oil will pour like what we consider a normal oil consistency. Since we want the oil to "stay" on the gears to act as a lubricant between the metals we need the appropriate weight oil for the temperature it will be running at.
I still remember (and have the scar to prove it) this time a Kenworth came in to the shop after just getting off from I-5. He said he had been traveling for over 10 hours (probably more, log books lied a lot back then) coming up from California. He wanted both his differentials oil changed out. Since I was the youngest mechanic at the time I got the job. What I didn't know at that time was how hot gear oil could get ! Also it will not flow but "spew" out at high temperatures ! Also, instead of just dropping the drain plug I thought I would catch it so I would not have to get all dirty looking for it in the drain pan. WRONG !!!! I got a severe 3rd degree burn along my hand and arm. The older mechanics all stood around telling me what I did wrong. Of course it would have been better if they had told me "before" it happened ! I guess those old farts felt it would be a better learning experience if I found out on my own. I still think they where just sadistic bastards who liked watching someone in pain.
 

Floridianson

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When I was young I stuck my Johnson in a light bulb socket. Now all the girls say I light up there life. Go figure!

My opinion there are more than a few great mechanics on SS. When I joined in 06 there were 20 people that knew there stuff and helped me play catch up with the green iron. I would say they are the founding Fathers. Most don't post much any more and maybe they got tired of answering the same old questions about which way do I turn the steering wheel to go left. There is still plenty of guys that know there stuff and still helping others. Thanks be to the givers.
 
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41cl8m5

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I agree. I don't chime in much on posts here at SS, but I do try to look at what folks are talking about at least every other day if I can. I will add from experience or from what I have seen. I was told by my father at a very young age that once you think you are an expert at something you will become obsolete real quick, never stop learning, each day a person you come into contact with may know something you don't, the hard part is finding out if it good or bad information.

Now the topic of this thread is "What is the Best gear oil?" Great question but it's not an easy answer, great info from all. But what is the frame of mind the question being asked? I took it as, the person is getting ready to perform a change out of axle gear oil only and was wondering what others had luck in using. But if the person is thinking of doing a complete axle preventative maintainace job than re packing the wheel bearings is also part of that function. On normal automotive axles the gear oil travels down the tube and the wheel bearing will get lubed, not on these big axles.
 

rustystud

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When I was young I stuck my Johnson in a light bulb socket. Now all the girls say I light up there life. Go figure!

My opinion there are more than a few great mechanics on SS. When I joined in 06 there were 20 people that knew there stuff and helped me play catch up with the green iron. I would say they are the founding Fathers. Most don't post much any more and maybe they got tired of answering the same old questions about which way do I turn the steering wheel to go left. There is still plenty of guys that know there stuff and still helping others. Thanks be to the givers.
Why would you stick your "Johnson" in a light socket ?
So you don't like my little " Life lessons" ? I guess you had to be there to appreciate it.
I also agree that there are quite a few good mechanics here. Also there are several who are not mechanics but have learned a lot about the Deuce in the pursuit of the hobby. All in all most people can get a good answer to there problems here.
 
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