Hubs - how hot is too hot?

[arno]

Hey folks,

I recently did a brake service and bearing repacking job on my Deuce rear axles. The right two hubs on the rear axles run remarkably hotter than all the other hubs on the truck. I noticed there is a thread on hubs running hot, but what temperature is tolerable and what is too hot? The hot ones reach about 45-50° Celsius after half an hour drive whereas the cool ones are around 30°C.
The bearing ring and rollers looked okay but I did not check the seal binding to the outer bearing ring.
It is not the brake dragging, the drums are cool to the touch.
I set the play on all bearings (the cool ones and the hot ones) by tightening them to (IIRC 50Nm) while turning the hubs, then backing off 1/8 turn, as it is stated in my repair manual.

As I want to run the truck around 1500km next week, I'd like to be confident with that.

Greets

Arno

 

[frank8003]

Too hot means too hot to touch. When in doubt back one off a flat.
50C° is right about too hot to touch for me

30C° to 45C° to 50C° is 86F° to 113F° to 122F°
Are all the seals from China or just some of them?

I assume that GAA was used in all the bearings or at least all the same type of grease.
Sometimes the opposite is true so I question the coldest running bearing.
I assume the tires are not to mismatched, the truck was unloaded, the axle vents are clear, all the same type/brand seals were used, none of the cork seals have leaked thru, and you used new star washers or ground them flat.
Some have found good results with the following:
The assembly was spun and checked for play after the outer nut was tightened as just a bit of dirt on threads will mislead a torque wrench.
The locking nuts were ground or stoned flat and the same ones removed were replaced same location?

This works for me
When the wheel bearing nuts are properly adjusted and tightened, you should be able to feel a slight bit of motion when you grab the outside edges of the tire and rock it by alternately pushing with your left hand, while pulling with your right, and then pulling with your left hand while pushing with your right... But you should not be able to see the motion.
So just back off one "hot" one and drive it around some more and check again.

 

[arno]

Hi and thanks for your reply.
Regarding the seals, I dont know. I used the ones that were already on the truck as they were not leaking too badly. Put in RTV instead of the cork, all tires are same size and new, the vents are new, the star washers are new... I dont know what GAA is, but I assume you mean the lube - yes, same lube on all bearings. I did not grind down the locking nuts, will do that... And will also check for play in the way you described... Will be back on thursday...
And thanks for confirming that hot to the touch is way to hot...
Best regards

Arno

 

[frank8003]

Hi and thanks for your reply.
Regarding the seals, I dont know. I used the ones that were already on the truck as they were not leaking too badly. Put in RTV instead of the cork, all tires are same size and new, the vents are new, the star washers are new... I dont know what GAA is, but I assume you mean the lube - yes, same lube on all bearings. I did not grind down the locking nuts, will do that... And will also check for play in the way you described... Will be back on thursday...
And thanks for confirming that hot to the touch is way to hot...
Best regards Arno

 

[frank8003]

Hi and thanks for your reply.
Regarding the seals, I dont know. I used the ones that were already on the truck as they were not leaking too badly. Put in RTV instead of the cork, all tires are same size and new, the vents are new, the star washers are new... I dont know what GAA is, but I assume you mean the lube - yes, same lube on all bearings. I did not grind down the locking nuts, will do that... And will also check for play in the way you described... Will be back on thursday...
And thanks for confirming that hot to the touch is way to hot...
Best regards Arno

View attachment 686697View attachment 686699

It says inner nut 68Nm
It also says back off 1/16 to 1/4 turn.
There is leeway there.
Too loose will wobble but not fail, too tight and the
heat signature indicates too tight if nothing else is wrong.

 

[cattlerepairman]

I know exactly how these two warm hubs bug you! I had the same happen on the same two hubs (right side, both rears). They were not "hot" to the touch, maybe "very warm" and definitely warmer than the other four. My definition of "not hot" is that I can place my hand there and leave it there. I also used NewStar parts, without modifying them. Apparently the outer seal can cause an issue due to being thicker (?).
I had to drive to an event, so I decided to watch the hub temp, even stopped on the way to measure with the laser thermometer. After about 300 km they ran the same temp as the other four. Whatever caused the initial higher friction settled itself. No issues since.
Good advice on "feeling" the wobble/looseness for right preload of the bearings.

 

[Floridianson]

If I remember Ray aka tow 4 did his oil floating and they were around 120*. I had just done one of mine trucks with grease and the rear rear was running around 120* F checked by lazer.

 

[gimpyrobb]

Ive been told by a career big truck mechanic that if you can't keep your hand on it, its too hot. He says too tight will ruin bearings but a tad loose and your golden.

 

[rustystud]

Ive been told by a career big truck mechanic that if you can't keep your hand on it, its too hot. He says too tight will ruin bearings but a tad loose and your golden.

That's right Chris. In fact most hubs should have about .002" - .005" clearance due to heat expansion of the bearings.

 

[arno]

Experts,
what I will do on saturday:
- check the bearing for slight play by wobbling on wheel
- keep an eye on the temp
- drive for 100~200km
I will have new bearings with me so in case things get worse, I can change them for new ones. But I suspect the seal, because the rise in temp is only on the outside of the hub.
Greets and thanks

Arno

 

[Floridianson]

Ive been told by a career big truck mechanic that if you can't keep your hand on it, its too hot. He says too tight will ruin bearings but a tad loose and your golden.

Most of the time they don't have to deal with that outer grease seal. So I believe two tad's too loose and the outer grease seal will leak.
Remember the one we did for Chris's dad at the Ga. rally that was just done by a shop a week before. Before I took off the bearing nut I tighten the nut up to see how loose it was and it was over one turn loose from the 50 lbs. tight. That one was four and a half tad's too loose. Where most call for 1/4 turn I like 1/8. Yes the proper way would be dial indicator.

 

[arno]

Experts, just want to share what happened:
Loosening the nut on the hottest hub led to nothing. So I went on my Trip. After 50km the right two hubs were really hot, cheched with an infrared Thermometer. But then, the temperature started to drop. Now, after a 1500km Trip, the right hubs are still slightly hotter than on the left side, but that is marginal - driving 250km before the measurement gave 45 Vs 52 degree
Thanks for your help, Arno

 

[CMPPhil]

Hi Arno

It sounds like you have found and corrected the bearing temp. But a question how much crown in the roads you are driving on? I've notice with my 3Ton CMPs that the right side bearings and tires tend to run warmer than the left particularly when driving on high crown secondary roads.

For a couple of years I've been logging all the critical temps on the trucks with an IR gun amazing what you can spot when you have data over time.

Cheers Phil

 

[CMPPhil]

Hi Arno

It sounds like you have found and corrected the bearing temp. But a question how much crown in the roads you are driving on? I've notice with my 3Ton CMPs that the right side bearings and tires tend to run warmer than the left particularly when driving on high crown secondary roads.
For a couple of years I've been logging all the critical temps on the trucks with an IR gun amazing what you can spot when you have data over time. The one time I didn't pay attention to a sudden jump in one hub, I came close to loosing a left front wheel the next time I took the truck out. The increase was caused by the axle nut starting to back off. So your questioning the temp of the hub was a good catch.

Only problem I have with the right left tire and hub difference is that I've got 3-7 miles of high crown road getting in to the house from the main roads.

Cheers Phil

Cheers Phil

 

[gringeltaube]

I am pretty sure that the higher initial temperature was caused by the new outer seals, "wearing ïn". Question now is, how long would such a seal last doing its job... after the rubber lip has seen that much friction and heat?
Just out of curiosity I would check and measure the lips' remaining width and compare it with that of a new part.

If we were talking about "Newstar" quality, my theory has always been that due to their very limited flexibility/resiliency they would simply wear down relatively fast to where there is almost no more interference - or say pressure exerted - against the bearing cup.
That's why I preferred to modify those by reducing their interference, before installation. (described here...)

 

[arno]

Hi CMPPhil, the roads I drove on had very little road crown (mostly urban roads and autobahn).
@ Gringeltaube: I used the seals that were already on the truck. But I have no idea if they are new or old. I guess they are old, because the truck showed signs of neglect when I bought it...
I check regularly for leaks and dont have a lot of oil spray so i hope the seals will last a few more miles

Greets
Arno