M1078A1 Rear hubs getting hot

[rcmartin]

I am a member of a rural volunteer fire department in Montana and we recently acquired a 2002, M1078A1 truck to use as our wildland fire engine. Our problem is that after we drive it, the rear hubs and wheel get hot. Approximately 150-200 degrees according to our TIC. Is this normal for a M1078A1? If not, has anyone else experienced this issue and what was your fix?

Thanks, Robert

 

[simp5782]

I am a member of a rural volunteer fire department in Montana and we recently acquired a 2002, M1078A1 truck to use as our wildland fire engine. Our problem is that after we drive it, the rear hubs and wheel get hot. Approximately 150-200 degrees according to our TIC. Is this normal for a M1078A1? If not, has anyone else experienced this issue and what was your fix?

Thanks, Robert

Synthetic gear oil

Temp would also vary depending on the load on it.

M1079 check those hubs!

I bought my LMTV M1079 back in October and am new to the military vehicle stuff but I have had a lot of advise from Steel Soldiers. I took my truck to the GA rally and got a lot of great information. I had only had the truck a couple of weeks but I took notes from what everyone told me. One of...

www.steelsoldiers.com

 

[Ronmar]

Well the hubs share lube with the differential, but I would make sure there is oil out in the hubs and that the axle lube is up to it’s proper level. You check the hubs by putting it on a jackstand, removing a filler port on the hub and rolling the wheel till the port is at the 4 O-clock position. Rotating it any farther down should result in oil running out The port. If it doesn’t your hubs were low. The rear hubs should get oil from the center along the axle passage, but it never hurts to check that it is actually out there. This is also a good time to roll it to 6 O-clock and drain and inspect that oil that comes out for metal shavings… then you can roll it upright and add 11-13 oz of new 80W90 gear oil. You cannot really overfill the rear hubs as it just runs back to the center, the proceduer with the 4 Oclock position must be used to check and set the front hub level every 3000 mi as there is no connection with the center axle on the fronts. This procedure is in the manuals you can download here from the manuals section if you have not already. They are A0 manuals, but the chassis procedures are the same…


Next I would look at is brake adjustment and that the park air circuit is properly compressing the park springs/releasing the park brakes. The Front and rear systems are also separate, fed with different halves of the same treadle/pedal valve. If the rear is leaking air into the system it could be holding the brakes partially engaged, the same as if someone was riding a pedal… you can check for this by removing an airline from an actuator and seeing if any air comes out/pressure builds up. You should only get air out to the actuators when you step on the brake Pedal…

Dragging brake shoes can make a LOT of heat… the brake check and adjust procedure is also in the manuals, but if I recall you want to be able to slip a .020-.040” feeler gauge blade between shoe and drum at the middle of each shoe arch when they are released… a quick and dirty check though is to compare how much drag is felt while rotating a wheel compared with rotating a wheel that is not getting hot…

 

[Floridianson]

K.I.S.S. first a short ride and then feeling the drum not the hub will tell you if the brakes are sticking. Then we get into our hubs. Most of us have the tools / cut off hub so when we remove the hub to check outer set up and inner greased bearings so we can put it back together right. So at this point I should not assume but I will you do not have the tools and shims to set up the hub after removal / service. Now yes if you want to check to see if there is too much metal in the rear axles/ hubs you can rotate the fill plug to 6 o'clock and drain a little out and look / check magnet. Problem it could be the inner grease bearing but as said if you do remove the hub you need the tools to set it up. So back to draining a bit of the rear hubs to check oil but you do not need to drain that much. Then after you have checked both sides axles level or back on the ground plugs back in just fill the rear axle through the axle fill plug till it runs out. Then let it sit awhile and double check oil level in axle ( center of axle fill plug) is full. Could be the rear axle is very low on oil but myself having the tools I would pull the hub check inner grease bearing or new grease and seal then work my way out setting up the hub with shim pack. Then fill to the top of the fill plug with correct oil and let it sit for awhile then double check fill plug has some oil right at the fill plug. I will say this do not trust that the last person to work on the axles if ever done that it was done right as I have seen them with parts missing. Yes guys someone left out the outer thrust bearing shim on one of my rear axles. This is why on any military truck I service the hubs / brakes first thing.

 

[Ronmar]

If you have to pull the hubs apart You can check and set the hub shim spec as mentioned above as seen in one of Neil’s videos with a custom machined fixture.

Or you can use the Meritor procedure shown in the manual and demonstrated in this video…

Either method works, you just need the parts to equal a particular stack height…

 

[Floridianson]

Here is the way it is done using a cut down hub or something that is made to hold the cross in place. My .02 Steve's way takes wear of the parts into thought and we can feel the 10 to 20 thousands min. clearance. Also easy way to understand what we are looking for if you have never set up a geared hub. Good thread started by Steve to help us out.
As for the Utube love it when he goes to put the hub on and the thrust washer and thrust bearing fall out. Here even if we are installing the outer hub cover when the on the truck we must put grease on the thrust washer and thrust bearing to hold them in place for install no if's and buts. M1078 LMTV planetary hub setup | SteelSoldiers

 

[Ronmar]

Here is the way it is done using a cut down hub or something that is made to hold the cross in place. My .02 Steve's way takes wear of the parts into thought and we can feel the 10 to 20 thousands min. clearance. Also easy way to understand what we are looking for if you have never set up a geared hub. Good thread started by Steve to help us out.
As for the Utube love it when he goes to put the hub on and the thrust washer and thrust bearing fall out. Here even if we are installing the outer hub cover when the on the truck we must put grease on the thrust washer and thrust bearing to hold them in place for install no if's and buts. M1078 LMTV planetary hub setup | SteelSoldiers

The cut hub cap is good because you can use a dial indicator to measure the actual gear mesh/lash and compare it between hubs as you build them…

 

[Floridianson]

Guess a cool test would be if someone would take the time would be set up dial indicator way then check with cut of hub. Would think as long as there is some clearance is much better than to tight. I am no good at ciphering so I just did Steve's way because I had a hub that was bad and had it cut down. First one of the six I did on my truck took longer then the rest but found the rest went faster.

 

[rcmartin]

Well the hubs share lube with the differential, but I would make sure there is oil out in the hubs and that the axle lube is up to it’s proper level. You check the hubs by putting it on a jackstand, removing a filler port on the hub and rolling the wheel till the port is at the 4 O-clock position. Rotating it any farther down should result in oil running out The port. If it doesn’t your hubs were low. The rear hubs should get oil from the center along the axle passage, but it never hurts to check that it is actually out there. This is also a good time to roll it to 6 O-clock and drain and inspect that oil that comes out for metal shavings… then you can roll it upright and add 11-13 oz of new 80W90 gear oil. You cannot really overfill the rear hubs as it just runs back to the center, the proceduer with the 4 Oclock position must be used to check and set the front hub level every 3000 mi as there is no connection with the center axle on the fronts. This procedure is in the manuals you can download here from the manuals section if you have not already. They are A0 manuals, but the chassis procedures are the same…


Next I would look at is brake adjustment and that the park air circuit is properly compressing the park springs/releasing the park brakes. The Front and rear systems are also separate, fed with different halves of the same treadle/pedal valve. If the rear is leaking air into the system it could be holding the brakes partially engaged, the same as if someone was riding a pedal… you can check for this by removing an airline from an actuator and seeing if any air comes out/pressure builds up. You should only get air out to the actuators when you step on the brake Pedal…

Dragging brake shoes can make a LOT of heat… the brake check and adjust procedure is also in the manuals, but if I recall you want to be able to slip a .020-.040” feeler gauge blade between shoe and drum at the middle of each shoe arch when they are released… a quick and dirty check though is to compare how much drag is felt while rotating a wheel compared with rotating a wheel that is not getting hot…

View attachment 838182

Thanks for the info, I appreciate it. We purchased a manual, so hopefully we will be able to trouble shoot it.

 

[rcmartin]

K.I.S.S. first a short ride and then feeling the drum not the hub will tell you if the brakes are sticking. Then we get into our hubs. Most of us have the tools / cut off hub so when we remove the hub to check outer set up and inner greased bearings so we can put it back together right. So at this point I should not assume but I will you do not have the tools and shims to set up the hub after removal / service. Now yes if you want to check to see if there is too much metal in the rear axles/ hubs you can rotate the fill plug to 6 o'clock and drain a little out and look / check magnet. Problem it could be the inner grease bearing but as said if you do remove the hub you need the tools to set it up. So back to draining a bit of the rear hubs to check oil but you do not need to drain that much. Then after you have checked both sides axles level or back on the ground plugs back in just fill the rear axle through the axle fill plug till it runs out. Then let it sit awhile and double check oil level in axle ( center of axle fill plug) is full. Could be the rear axle is very low on oil but myself having the tools I would pull the hub check inner grease bearing or new grease and seal then work my way out setting up the hub with shim pack. Then fill to the top of the fill plug with correct oil and let it sit for awhile then double check fill plug has some oil right at the fill plug. I will say this do not trust that the last person to work on the axles if ever done that it was done right as I have seen them with parts missing. Yes guys someone left out the outer thrust bearing shim on one of my rear axles. This is why on any military truck I service the hubs / brakes first thing.

Thanks for the info, we do not have the tools, but we can take for a short ride and check and see if brakes are dragging. And we can rotate the fill plug, I think! LOL. Thanks for the advice!

 

[Floridianson]

Yea you do not even need to jack it up just have someone watch and do one side at a time. Be sure to use the correct size Allen wrench. One of mine was all ready in bad shape and had to drill it out. Trouble was when I hit the magnet drill stopped and I had to remove the cap and tap it out towards the inside. Good thing I was going in deep anyway.
I sold my truck and wanted to double check the front hubs before he came and got it. O no I stopped the truck / tire at 3 o'clock by myself what do I do. Removed the Allen plug took a piece of wire and bent it 90* and long enough to reach down below the 4 o'clock position. Oil on dip stick good to go. Do not over think it just think.