Wheel bearing adjustment

[PP]

Need a little advice here please. Since doing my wheel seals on the drive axles, the bearings are running a little warmer than before and I'm thinking I may have preloaded them (over tightened). I set them according to the manual which called for torquing to 250 while rotating the wheel (I didn't have a helper either) and then backing the nut off 1 full revolution and retorquing to 50 before setting the locknut. Does that sound about right? Or did I miss something? Any experienced advice will be greatly appreciated. The seals aren't leaking and I don't want to have to do them again . I did figure out what started them leaking in the first place, and it wasn't my fault (honest)
Thanks in advance, Will
BTW-Gumpy and Buswarrior, everytime I tell people, especially mechanics in the local garage how I removed the wheels and hubs as a single unit on a greased highway sign with no lifting, they still shake their heads in disbelief! 

[Old4103]

Will,

Did you replace the oil that was lost in the end of the axles when you removed the hubs?

There should be a 1/4" plug on the end of each axle or on the hub housing where you can add the extra oil needed. Probably about a pint and a half on each end.

IHTH

Dallas

[JackConrad]

Just my way, but I repack the bearings with grease before re-installing them. then make sure rear end lubricant is full to bottom of fill hole in the differential. I feel that this insures adequate lubricstion to the bearings until the rear end lube works it's way back out to the bearings.  Jack
Note: this is just my way, and not based on anything "official".

[rv_safetyman]

PP I think your bearings are too tight.  I will check my manual tonight and make sure, but I believe that all of your steps are correct, BUT I think there is one last step in that you back off the nut by about 1/8 rotation.  I would not drive it until someone confirms the last step.

Most tapered bearings want to have some clearance. 

Jim

[Utahclaimjumper]

Most tapered bearings should be ZERO preload for best life.>>>Dan

[rv_safetyman]

I just checked my Eagle (model 10) manual.  The bearing adjustment is as follows:

1)  tighten nut to 100 ft-lb and rotate both ways (sets the races)

2)  back off nut completely and re-tighten to 50 ft-lb and rotate

3)  back off nut 60 to 90 degrees

4)  check for end play "must be in the range of 0.001 to 0.010 inches"

For the front bearings, I think that last two steps were missing.  I did not feel comfortable with the preload and checked with this board and got clarification.  The above is for the drive axle bearings, so the information should be applicable.

I hope someone with a Prevost will check their manual.  If it is the same, then I hope you did not drive very far.  Tapered bearings with preload tend to fry themselves very quickly.

Jim

[JohnEd]

Your correct, if there is any end play at all then there is zero preload.  and I don't think you need me to tell you that.

PP,

You are right on top of this.  Use your infrared "non contact" temp gun every time you shut down.  You can see a bearing heading out.  If one does fail it makes a heck of a mess.

Jack,

Rare opportunity for me here.  I was told by a mech that the diff oil would follow the axles out to the bearings.  That is a false piece of information.  Only on severe tilt will any oil migrate out and that may not happen for many many miles.  Packing the bearings is a absolute must on some setups but is a darn good idea on all.  If your bearings are diff oil lubed I think you absolutely MUST add oil thru the center hole.  I don't think those need any pre grease and I would be concerned about compatibility and I would not use any soap based lithium product under any circumstance.

John

[PP]

Will,

Did you replace the oil that was lost in the end of the axles when you removed the hubs?

There should be a 1/4" plug on the end of each axle or on the hub housing where you can add the extra oil needed. Probably about a pint and a half on each end.

IHTH

Dallas

Dallas,
Yes. I put almost exactly a pint in either side and lifted the axle on each side as high as it would go (to the rubber stop) while leaving the opposite side on the ground. Then I checked the pumpkin fill hole and oil ran out. Thanks for the heads up,

Just my way, but I repack the bearings with grease before re-installing them. then make sure rear end lubricant is full to bottom of fill hole in the differential. I feel that this insures adequate lubricstion to the bearings until the rear end lube works it's way back out to the bearings.  Jack
Note: this is just my way, and not based on anything "official".

Sorry Jack,
But everyone and every piece of literature I could find definitely stated that in NO circumstances should you pack the bearings with grease, it only restricts the flow of the oil to the bearings. I thought of doing it and checked before I did because it sounded logical. Thanks,

PP I think your bearings are too tight.  I will check my manual tonight and make sure, but I believe that all of your steps are correct, BUT I think there is one last step in that you back off the nut by about 1/8 rotation.  I would not drive it until someone confirms the last step.

Most tapered bearings want to have some clearance. 

Jim

Jim,
I think you just hit my nail on the head. It sounds like I need to back the nut off a quarter of a turn or less. I've only put about 100 miles on it since doing the seals and I checked them about 20 down the road and they were still cool at that point. They never heated up, just felt warmer than before I did the seals. Hopefuly the weather will be good tomorrow and I can go through the adjustment again. This time I will back them off as stated. So I won't lose much oil and since I don't have to slide them off the hub for this, I think I'll lift the side I'm working on as high as possible so the oil stays in the pumpkin. I don't have any means of measuring the endplay, but I think I can do better than they are now.
Thanks for all the great advice. I have 2 big Prevost books, blueprints on the conversion, Detroit Diesel manual, and somewhere along the line, someone pulled the pages referring to the drive axle. Just my luck

[rv_safetyman]

Will, in truth, I really doubt any mechanic would check the end play.  That would take a pretty good dial indicator/mount and would be quite time consuming.  The reason I put that step in the post is two fold:  1)  that is what the book says 2)  I wanted to point out that there should be clearance (end play) in the bearing.

I am very sensitive to this adjustment.  First of all, I used to teach a class for plant mechanics and that was an important part of the tapered bearing section.  Secondly, many years ago, I adjusted the front bearings on a VW bus camper and did not get enough clearance.  I fried the bearings (bad) in about 20 miles.

This adjustment will be easy.  No need to pull the wheels and drum.

While you are in there, I would pull the outer bearings to make sure that they are OK.  That will take a bit of jockeying on the wheels/drum, but I think it is worth it.  I would also check the temperatures a few times the first day, but that is just me.

Jim

[06 Bill]

PP
Never could figure why no wheel brg preload. Rear end brgs. pinion & carrier have pretty good preload as well as many industial apps. Even some ball brgs made for side load get loaded. I find as 35 year wrench as close to zero clearance with no load works best for wheel brgs. Does not allow road shock to do its thing over time. 06 Bill

[PP]

Jim, I'm about to go into it as soon as I finish my java this morning. I intend on inspecting the outboard bearing and if it seems okay I'll trust that the inside is too. Thanks again for all the advice. You too, Bill. What you suggest about very little endplay makes sense with regard to road shock.
When I picked up the seals, the wrong axle gaskets came in so I had to make my own. Fortunately, I have enough material left for another pair. Funny how these things work out
I'll let you all know how the bearings look,
Will

[rv_safetyman]

Warning:  long technical discussion to follow .

We need to be very careful when we talk about preloading a set of tapered bearings.  

In general, tapered roller bearings need some end play (clearance).  That is the case on automotive wheel applications.  It is also true of most, but not all, machine applications.

There are many applications that use a crush sleeve to maintain a very tight tolerance spacing between tapered bearings in order to accurately control end play.  Some use a sleeve and shims.  In most of these applications, you use a dial indicator to set up the bearing assembly (to check amount of end play).  When you work on those types of applications, you do apply quite a bit of torque to a locking nut.  That is not to be confused with applying "clamping forces" to two tapered bearings that do not have controlled spacing.

In addition to designing tapered roller bearings to handle thrust loads (such as on the side load of wheels in corners), tapered bearings are used to very accurately locate mechanical components such as gears.  In this case, there is some very carefully controlled preload on the bearing.  The bearing capacity is designed to take into account the thrust load of the gear and the affect of the preload.  Generally, these applications are submerged in oil so that heat is carried away from the bearing.  An example of this are the pinion bearings in a rear end.  When you read the manual, you will see that it is quite an exacting process to get a very accurate preload on the bearings.

Getting back to the basics of tapered bearings, the problem is that these bearings are indeed tapered.  A taper is the same as a wedge.  We all know that a little force on the end of a wedge causes a BIG force on the separating surface of the wedge.  In the case of these bearings, that huge force is exerted on the inner race/rollers/outer race.  

Tapered bearings are designed to take very large side loads in a wheel/axle type application.  If we tighten the bearing (preload), we use most or all of the thrust capacity of the bearing.

If you poke around the internet, you will not find much general information on tapered bearing maintenance.  This is partly a result of the fact that they are rather application specific.  One process does not fit all applications.  The following gives some general information:

http://motionsystemdesign.com/mag/adjusting_tapered_bearings/

[rv_safetyman]

Will. 

A fellow contacted me off line and confirmed that the Prevost bearing adjustment is almost identical to the Eagle.

By checking the outer bearing, you can be reasonable sure the inner bearing will be in about the same condition I would think.  At least you will have a better idea if you did any major damage.

Jim

[buswarrior]

From the belt and suspenders crowd....

If you want to make a mistake, it's better to be a little loose than a little tight, when it comes to wheel bearings.

A little wheel bearing grease to get the bearings started in an oil bath set-up is not uncommon, and many grizzled wrenches report having never suffered a problem due to the practice.

Great pictures, PP!

happy coaching!
buswarrior

[wrench]

"BTW-Gumpy and Buswarrior, everytime I tell people, especially mechanics in the local garage how I removed the wheels and hubs as a single unit on a greased highway sign with no lifting, they still shake their heads in disbelief!  "
[/quote]

         Can I know about that process?  Or will I have to entertain drink or diner?
                 wrench