M929A1 Rear Axle Heat Difference

[red]

So we have the two great 5 ton race truck builders in here but we can't figure out whether the hubs are grease or oil? For shame...

So where does that leave us? Well let me see if I can ass-ist.

The rear hubs are originally grease lubed. There is an inner and outer seal on the A0/A1 trucks. If the inner seal leaks then gear oil will travel to the bearings. This is fine, and how I run my truck, AS LONG AS the outer seal is good. If the outer seal leaks then you end up with oil in the brakes.

So, in your picture Jaws4518, there is no grease in there. You say the seals are good so this would mean no oil either. That looks pretty dry to me. I think someone forgot the grease at rebuild. Wouldn't be the first time someone found this problem. Did any oil come out when you pulled the axle?

Take your pick, grease or oil bath. Both are fine. If you choose oil bath just make sure your outer seal is good so you don't soak the brakes. I've been running mine like this for about 2 years now. The bearings don't care what they're lubed with...oil, grease or a mix of both.

Costs a case of beer for me to open up the TM's for others and I do collect that haha.

Problem with the oil bath plan is the inner seal by the brakes, it's not designed to keep oil in, just to keep crap out.

 

[jaws4518]

Isn't it fun when nobody wants to check the manual? If I look at there is an outer seal, you'll need to sing the "I'm wrong" song Simp.

Poster is on the right path of being concerned and investigating. One rear should not necessarily be hotter than other rears at any given time. If all cool or all warm, then OK. One warm and 3 cold, that's a flag.

I will be following the TM instructions from this point forward. Someone said spin the axle checking for drag. Unless all 4 wheels are off the ground, I'm not spinning anything. So, I assume I must drop the propeller shaft on the rear to isolate it singly. When I re-worked my M818 bearings and brakes, I had the whole rear on jack stands, so this was not an issue. The reason I'm asking is I don't know of any other way? I don't have all four(s) removed or off the ground at this time.

 

[jaws4518]

No infared temp test. Just to the touch, and there was considerable difference. Too hot to leave your hand on it for more than 5 seconds. Explain the stuck wedge? I'm not familiar with this condition.

 

[Swamp Donkey]

Costs a case of beer for me to open up the TM's for others and I do collect that haha.

Problem with the oil bath plan is the inner seal by the brakes, it's not designed to keep oil in, just to keep crap out.

I was actually talking about the pair of dualing banjos and their little pee pee competition they have going.

You are correct that the seal is not designed for oil. In the grand scheme of things though it doesn't see that much of it and does pretty well. Leaving the bad oil seal in place helps to limit the amount of oil that enters the hub.

 

[Swamp Donkey]

I will be following the TM instructions from this point forward. Someone said spin the axle checking for drag. Unless all 4 wheels are off the ground, I'm not spinning anything. So, I assume I must drop the propeller shaft on the rear to isolate it singly. When I re-worked my M818 bearings and brakes, I had the whole rear on jack stands, so this was not an issue. The reason I'm asking is I don't know of any other way? I don't have all four(s) removed or off the ground at this time.

Jack up both ends of the axle you are working on. Since you are going by the TM now you need to cage both spring brakes on that axle, but there are other ways. Then you can spin both sides. No need to remove anything.

 

[jaws4518]

Thanks for all the replies. I hope my questions and replies are going to the thread. I'm new here, so I haven't spent much time on learning the forum interface details. Going to go pull this hub off now. I will post some pictures of what I find. Hopefully nothing!

 

[Swamp Donkey]

Made a couple changes to post #17 to better reflect TM nomenclature. I always forget the TM considers the inner and outer seals as inboard and outboard, as opposed to inside the hub and outside the hub.

 

[jaws4518]

Okay. I'm not familiar with caging the spring brakes, but I've seen the article and know what you are referring too. The M939 series truck with air brakes is new territory for me. I really like the simplicity of the 800 series truck. I'm sure working knowledge of the 939 series will come fast as I move along.

 

[74M35A2]

*crickets*

 

[74M35A2]

If you remove or leave off the outer seal, that is OK, but you will need to make sure both bearings have some type of initial lube before driving, as it does take some time for diff fluid to travel down to the end of each axle tube. Wad of grease in each is enough. This is spec procedure for semi trucks.

 

[red]

Caging the brakes. Insert the T shaped head of that bolt into the spring brake chamber, rotate it clockwise until it catches. Then thread on the nut/washer and use a wrench to pull it up tight.

 

[doghead]

Pull your axle shaft, to feel the bearing drag/play.

Jack up just the hub/ location you are working on.

Cage air-chamber on M939 series trucks.

This forum is the best forum because for many years we strive to keep posting with facts and experiance, and strongly advise to use the 100% factual documentation in the military technical manuals. We have them in the TM section.

As for the guys spitballing the answers(even though they were unsure), shame on you. Both for throwing unverified/unexperienced answers and for not servicing your own trucks and driving them on public roads.

There is NO reason to expect or beleive any military surplus truck is road ready and in 100% maintained condition. (shocker huh?)

 

[74M35A2]

https://m.youtube.com/watch?v=Tp-QPNz6e2M

 

[jaws4518]

Thanks! Believe me, there is no guessing around on this end. That's why I'm asking these questions and looking at the TM(s). Looks like the problem is a brake shoe dragging. So, I've got to adjust the brakes on that side. Might as well check them all as I replace the tires with new 395 XLZs. I'm not making any long trips until I check all hubs. I know I have a leak on the front>front-right side. That's next!

Maybe you can see the difference in spacing between top right shoe, and top left shoe. The top right shoe is dragging. Parking brake is off. Same effect if I push emergency spring brake to OFF.

 

[jaws4518]

Brain drag too!

Well, I forgot that when the axle shafts are pulled your hub is going to spin if the brakes are not en-gauged. It's been a few years since I have done this, plus a different brake system. Got the brake caged, so I'm ready to adjust, pack, and reset the bearing tension. I guess I'm good to go from here...

Thanks everyone!

 

[jaws4518]

Okay, just to clear up an misconceptions about grease or oil bath. You must grease the bearings, period! The TM says so! Yeah, oil lubrication is part of the equation, but they need to be packed with grease. Certainly not a 1/4 gallon per hub like I found on XM818. The hub cavities had more than enough grease in them. Anyway oil alone is not enough. I'm going to go ahead and re-pack every hub. I'm not going replace seals or wipers unless I find one that is bad. You can pack the inner bearing without taking it out, so it's not a big deal.

As one member said, I wouldn't wholesale trust the previous condition of these critical drive-train areas. Even though this truck has be worked over, I bet I find that all the bearings are too dry.

We shall see...

 

[jaws4518]

So.., the left-rear>rear looks good. Plenty of grease and oil mixed. I will go ahead and repack with grease while I have it apart. I feel very lucky to catch the right-rear bearing issue before a major failure. It was barely lubing itself with gear oil. If you haven't checked your wheel bearings in awhile, I would. Especially before a road trip, and after running through deep water over an extended period of time. this is not a difficult procedure once you get set up and going. I'm doing this myself. I think one wheel per hour at a normal pace start to finish.

 

[Swamp Donkey]

The TMs are like a hammer. As with a hammer, they are useful for a lot of things, but they are still just a tool. As with a hammer, they are not the proper tool for every job.

There are some documented errors contained in the TMs. Improvise...

Most troubleshooting work packages end with "notify supervisor" or "replace the major component". So what then, sell the truck? Nope, improvise...

There are many instances where the TM calls for major work to complete a simple task. For instance: Remove entire right rear spring pack, torque rod mounting brackets/hardware and tires to replace the upper torque rods. This requires removing multiple heavy parts and working under a vehicle on jack stands. Yet this same procedure can be done with a custom wrench while the truck sitting on the ground and no other parts removal except the item being replaced. Safer and easier. It's called improvising.

The TMs assume you have a complete motorpool of tools, parts, equipment and personnel. I have a ton of tools, a ton of parts, some equipment and no personnel. Doesn't matter because I still must know how to improvise...

I'm not anit-TM though. I'm more about use the TM as a guide, but know when to improvise. I use them a lot but they're still just a tool.

The LO (Lube Order) is also part of the TM collection for our trucks. Be sure to check it out to see the mileage intervals on repacking all those bearings. You'll be back in there shortly.

You should ask a few OTR truck drivers when was the last time they had their rear bearings repacked with grease. That should get you some odd looks and grins. They're all oil bath. Lower maintenance costs due to much longer service intervals and better lubrication.

The big proponent of "TM and forum approved procedures" in this thread, that is smacking hands and taking names, has a well publicized mod himself. It's actually named after him and is forum approved but, oddly enough, isn't found in the TMs. Sounds like he's a closet proponent of improvising too. Food for thought...

"Learning and innovation go hand in hand. The arrogance of success is to think that what you did yesterday will be sufficient for tomorrow." - William Pollard

The amount of oil you found in your hubs is not enough, but it takes far less oil to lubricate bearings than grease. I have a simple procedure I use for getting the proper amount of oil in the hubs but I'll digress since that is apparently frowned upon here...

 

[tobyS]

Enough seals and bearings for a total rear replacement, including that pesky outer seal.

https://www.steelsoldiers.com/showthread.php?172006-5-ton-rear-axle-bearings-and-seals

Make an offer!

 

[doghead]

SD, I think you missed the whole point of my post.

Oh well...

No need for further discussion in this thread.