Unit Hub/Bearing and Axle Nut torque

[Alpine Jim]

My '99 has about 157k on the ticker and I am getting a noise which I think may be a front wheel bearing going out. I am considering replacing the bearing assemblies on both sides just for the sake of maintenance if nothing else. I have only had it for 9 months or so, and I am planning on keeping it long term.


I find no discernable play in the front wheels (12 o'clock - 6 o'clock check) but the noise sounds similar to other wheel bearings I have heard on some of my other cars. I guess it could be the tires - they are cheapo no-name street tires (Milestar??) with less than 5k on them - but I see no odd wearing and the alignment is good.


Anywho, long way to get around to my real question. I think this job is within my skills and abilities except I am worried about 1) not being able to break the axle nut free in the first place, and 2) getting it properly torqued after reassembling.

I have standard garage tools but no air tools– ½” ratchets and sockets (I will have to buy the 36mm socket) and a short piece of tube maybe 1 foot long which I could use to extend out my ratchet for more leverage. So, just how hard is it for a 150 pound guy to apply 175 lb-ft of torque?

 

[Bjorn86]

Torque should be easy, I just did both of mine and I'm 160 lbs. If you don't have one, go rent a torque wrench that goes up to 250 lb-ft. You can usually get one at Autozone/Oreilly. It's a fairly easy job. Also, make sure you have a 12-pt 13mm socket/wrench for the 3 unit bearing bolts.

 

[donthelegend]

Have you checked the u-joints on the front axle shafts? They can also make noises related to the wheels rotating, and are easy to check for play. You're going to have the axle shafts out anyways to do the wheel bearings, so you should make sure they're in good shape.

Onto the wheel bearings-
Make sure you have a 12 point 13mm socket as well (for some reason all my metric sockets were 6 point and I never thought about it till the first time I did this job). I ended up buying one in 1/2" drive so I could use a breaker bar to break those 3 hub bolts loose. Sometimes they aren't too bad, other times the rust on the exposed portion of the threads really makes them a pain.

You should buy a torque wrench that goes to 175 lb-ft of torque if you don't already have one, bearings are one thing that I always use a torque wrench on. Do you have a breaker bar? You'll need one for this job, a ratchet will probably not be long enough (even with the 1 foot cheater pipe) and you are much more likely to break the ratchet with a cheater pipe.

Is there much rust on this vehicle? I've actually broken 1/2" breaker bars before and had to go up to a 3/4" breaker bar on some XJs that spent a lot of time on salted roads.

So to summarize, tools that you'll definitely need:
-1/2" Breaker bar
-36mm Socket
-13mm 12 point socket
-Torque wrench

In addition to the normal tools you'll need to get the tire and brake caliper off, but those don't need anything special.

It's really not a bad job, but as usual, rust can definitely makes things much more difficult.

 

[5-90]

My '99 has about 157k on the ticker and I am getting a noise which I think may be a front wheel bearing going out. I am considering replacing the bearing assemblies on both sides just for the sake of maintenance if nothing else. I have only had it for 9 months or so, and I am planning on keeping it long term.


I find no discernable play in the front wheels (12 o'clock - 6 o'clock check) but the noise sounds similar to other wheel bearings I have heard on some of my other cars. I guess it could be the tires - they are cheapo no-name street tires (Milestar??) with less than 5k on them - but I see no odd wearing and the alignment is good.


Anywho, long way to get around to my real question. I think this job is within my skills and abilities except I am worried about 1) not being able to break the axle nut free in the first place, and 2) getting it properly torqued after reassembling.

I have standard garage tools but no air tools– ½” ratchets and sockets (I will have to buy the 36mm socket) and a short piece of tube maybe 1 foot long which I could use to extend out my ratchet for more leverage. So, just how hard is it for a 150 pound guy to apply 175 lb-ft of torque?

1) Get you a three-foot cheater pipe and breaker bar. I've snapped ratchet pawls on front stub nuts, and I find the extra length useful (and I've got 100# on you.)

2) GET A TORQUE WRENCH. A regular 1/2" drive will work, even if it doesn't go up to the full 185lb-ft (more on that in a moment.)

3) You'll need a 12-point 13m/m socket for the retaining screws, bearing assembly to knuckle.

4) Get a pot of never-seez.

5) Your new bearings should come with new stub nuts - if they don't, get them. (If they come with new retaining screws, that's also helpful - but far less critical...)

Tips:

- Remove the stub shaft nut before jacking the wheel. Trust me - it's easier that way! Just don't try to roll the vehicle anywhere once you've broken torque.
- A few moments with a wire wheel, chucked in a drill motor, to work over the threads on the stub shaft won't go amiss.
- You can flip the disc rotor around and use it as a slide hammer to pop the bearing assembly loose.
- You can also back the retaining screws IN enough to fully engage the threads (they should still be loose) and then use the steering to pop the bearing assembly loose (but I prefer to use the slide hammer approach.)
- While you've got the wire wheel in the drill motor, clean out the bore in the knuckle.

On assembly:
- Paint the splines on the stub shaft and the bore in the knuckle with never-seez. Trust me.
- Your 1/2" drive torque wrench should have no trouble with 75 lb-ft of torque for the retaining screws. If you use never-seez on the threads there, torque to 37-38lb-ft (I've explained why elsewhere, and verified it experimentally. I leave a search on the topic for the apt pupil.)
- Remember I said you didn't have to go to 185lb-ft for your torque wrench? Paint the inside of the new stub shaft nut with never-seez, torque to 92-93lb-ft. Proper tensile preload is important here! If you don't preload the bearings properly, service life will be sharply compromised! I've been doing the "never-seez and half-torque" method for more years than I'd care to admit to, and I've yet to have any trouble (in fact, lubricating the threads makes preload more consistent - but you have to remember your reduction values for various lubricants, from the "clean, dry" figures given in the FSM.) You don't want to use a "cheater bar" on a torque wrench, you'll screw up your applied torque. You don't want to guess at this, or you'll be doing your bearings again inside of six months.

But, unit bearings are well within the reach of the "driveway mechanic" using only hand tools - I've lost count of how many I've done, on various vehicles. Easy!

 

[Alpine Jim]

Thanks for the help.

Don - nice description - thank you.

One question though: I didn't think you had to remove the axle to replace the bearing assembly.... Brain freeze on your end or lack of good intel on mine? This is on the front, by the way.

 

[Alpine Jim]

5-90 -Thanks for the helpful info.

 

[Warlock1]

Thanks for the help.

Don - nice description - thank you.

One question though: I didn't think you had to remove the axle to replace the bearing assembly.... Brain freeze on your end or lack of good intel on mine? This is on the front, by the way.

You must remove the axle nut to replace the front unit bearings if you want to keep the axle that is in your housing now. Period. If you are replacing unit bearing and your axle, then you can pull them as a assembly.

 

[yossarian19]

The shaft is attached to / through the bearing. You can remove both, but to change the bearing you will need to remove the shaft from the bearing. It is much, much easier to remove the axle nut while the bearing is still attached to the car.
Consider going to a 3/4" drive breaker bar, as most 1/2" breaker bars I've seen will flex quite a bit when you apply enough torque to break / tighten an axle nut. Alternately, use an inflexible cheater bar - like a heavy pipe.

 

[5-90]

Thanks for the help.

Don - nice description - thank you.

One question though: I didn't think you had to remove the axle to replace the bearing assembly.... Brain freeze on your end or lack of good intel on mine? This is on the front, by the way.

The "axle"? No.

The halfshaft? Depends. Some people have found it easier to pull the halfshaft and remove the bearing while holding the halfshaft in a vise on the workbench, but it's invariably easier to put it all back together in situ.

I've not had to - I tend to remove the halfshafts as a piece if I'm replacing the Cardan joint, but not to change the bearing assembly.

For a cheater bar - if you can find Sch80 iron pipe, use that. If you can't, use Sch40 and work slowly (smooth, even force is going to be more reliable, more productive, and less error-prone than just yanking. Given a choice between hauling on a short bar or using a longer bar, I'll use the longer bar every damn time...)

 

[Keekleberrys]

I'm lazy so I've always just hammered them on a good bit with the impact, never had a problem.

Torque wrenches aren't really a precision instrument when it comes to clamping force anyways. especially on something as rusty as spindle nuts.

 

[kastein]

I have had bearings burn up fast if I did that, so I torque them... the spec is 175 not 185, by the way, at least for a 96. I doubt there is much difference between those numbers in practice however.

sch40 pipe is fine as a breaker, I've used it with my 3/4" breaker bar (iirc 1" pipe fits perfectly over the HF 3/4 breaker bar) to remove axle nuts that broke two 1/2 breaker bars, a craftsman 1/2 ratchet, and defeated my IR231c rattle gun overpressured to 130psi the day before... even with heat.

Have also removed dana 60 pinion nuts rusted in place after being torqued to 230 foot pounds a decade ago. No sweat, the pipe and breaker bar handled it fine.

 

[5-90]

I'm lazy so I've always just hammered them on a good bit with the impact, never had a problem.

Torque wrenches aren't really a precision instrument when it comes to clamping force anyways. especially on something as rusty as spindle nuts.

Which is why I said to use a wire wheel on the threads (to strip the rust) and to lubricate (allowing more consistent tensile preload WRT applied torque.)

Seriously - this is a relatively complex subject, and I do not want to go through it all again... Search it up, you'll find a fairly detailed writeup by me here, giving experimental results, correction factors, and the like.

And, I probably got it crossed with the Pitman shaft nut - I think that one is 185 lb-ft. Check my site (www.kelleyswip.com/tech.html) - if I've gotten my grotty little paws on an FSM in some format, I've put specs up there.

 

[RedHeep]

We did a shaft and a bearing in a muddy ice pool on the trail yesterday with an impact and some hand tools.

Sometimes you guys just think too much.

 

[kastein]

It is almost like bearing preload has a massive impact on bearing life. Do as you wish on your jeep, and have fun replacing bearings more often than you would otherwise have to. I will torque mine, personally.

 

[RedHeep]

It is almost like bearing preload has a massive impact on bearing life. Do as you wish on your jeep, and have fun replacing bearings more often than you would otherwise have to. I will torque mine, personally.

You have to drive them to wear them out

I work on airplanes for a living. I understand all of the technical aspects of what you and 5-90 are discussing about torque. I just think you get a little too geek about the whole thing.

 

[donthelegend]

Forgot I posted in this thread... to clarify what I meant about having the axle shaft out, you don't actually have to remove it to replace the bearing, but there isn't anything left holding it in place and if you have to replace the u joints, you get to repeat the process of removing the hub.

Plenty of evidence around that improper torque on bearings is not good, and having a1/2 inch drive torque wrench is useful for many things, there is really no reason not to buy one and use it while working in your garage or driveway. On a trail, whatever gets you home is fine, but why do a quick shortcut when you've got all the time you need?

 

[Keekleberrys]

Plenty of evidence around that improper torque on bearings is not good, and having a1/2 inch drive torque wrench is useful for many things, there is really no reason not to buy one and use it while working in your garage or driveway. On a trail, whatever gets you home is fine, but why do a quick shortcut when you've got all the time you need?

Common sense will get you just as far as a torque wrench, unless you wire wheel and clean the threads for every fastener you remove on your car you might as well be throwing darts at the actual clamping force you will get which can vary by over 20%. The more useful application of the torque wrench there would be to measure the rolling torque of the bearings after you preloaded them.

Torque wrenches are not a precision instrument in terms of clamping force except in the fantasy world of the engineer that specified the fastener. A flat rate tech does not have time to clean every nut and bolt on a car.

They are ball park enough that they keep parts hangers from breaking things, plain and simple.