Unit Bearing mounting bolts?

Anybody tried using hex head bolts in place of the reverse torx head?

What size bolt will I need?

The dealer wants $7 each for these

I'm trying to remember from last time I did one, I think they were 12 point not torx. Hex bolts should work fine, as long as there's room to get a socket on them. Or maybe an allen head cap screw. Just make sure to use grade 8. and use a hardenened washer under the head so they torque down correctly.

They're 12-point, not Torx (of either variety.) I believe that they're M8-1.25 threaded, but I don't recall the length.

I would probably use a socket head capscrew there before a hex head - the socket heads offer more strength anyhow (they're almost always heat-treated to SAE Grade 8 or ISO Property Class 12.9, and the section change at the head is smaller than for a hex head.) Also, I don't seem to recall there being an awful lot of room there - another advantage for a socket head, or for a 12-point (more contact area with a smaller effective screw head.)

I would definitely use a hardened washer under the screw head, tho. And, I don't think I have actual dimensions on file for those screws - so if you could confirm that they are M8-1.25 (I'm fairly sure they are) and let me know the length under the head for the screw, I'd appreciate it.

whatever you end up using, coat the threads with something before installing

and then don't forget to reduce the torque on the bolts!!

Fred85 said:

whatever you end up using, coat the threads with something before installing

and then don't forget to reduce the torque on the bolts!!

Click to expand...

If you use LocTite, no need to change.
If you use engine oil or chassis grease, reduce installation torque by one-third.
If you use anti-seize, reduce installation torque by one-half.

Installation torque for the hub assembly mounting screws is 75 pound-feet, and torque for the stub shaft nut is 175 pound-feet. When using never-seez, I'll usually torque the screws to 38 pound-feet and the stub shaft nut to 88 pound-feet.

I'm not sure of the thread size/pitch but the head is a 12 point 13mm and not torx.

Later,
Joe

Thanks everyone, I need these for trail spares and didn't have one out to look at and measure.

Since we are on this subject what is the size of the shaft nut (large one). I think I have the right socket - but there is a little play in it on the nut. But I did bust my 1/2 breaker bar, so I am assuming the socket is the correct size since it busted the bar. Just checking cause I plan on buying a 3/4 breaker bar and have to buy the socket as well. Thanks

Its 36mm and youd want 6 point. I broke a couple breaker bars and used a 3/4" breaker with a 1 7/16" socket (they had no metric). Do that and heat and you'll be set.

As I recall, either a 30m/m or 1-1/4" six-point socket will work - but the thread pitch is ISO (metric,) so stick with a metric socket - and use a six-point, since that gives you a "better grip" on the nut.

I'd be loath to use head on that shaft tho - that's the end of your axle, and you could end up wrecking the heat treatment. Just like a weld has a "Heat Affected Zone," or HAZ, that depends largely upon the process used, penetration achieved, amount of heat, and original heat treatment (and sometimes requires post-weld heat treatment,) your axle shaft has been heat-treated to certain properties, and the use of heat to loosen the nut may cause the same problem. Any heat past 400*F will result in some annealing (softening) of the base metal - which can be bad.

I've had good luck in using a 3/4" breaker and socket, and using a pipe extension. Set it up so that the pipe is nearly horizontal - having to press DOWN to loosen (the pipe should extend to the LEFT side of the nut) and you can use your body weight at various points on the pipe, applied gradually, to break the nut loose. Once you've "broken" it, it should be rather easier, since the interference caused by the installation torque will be greatly reduced.

Again, I'd consider heating that nut to be a "weapon of last resort" - and I'd only do it if I was replacing the hub bearing assembly AND the axle shaft anyhow. But that's just me...

36 mm

post issue - sorry

post issue - sorry

I checked the socket I was using and it was a 1 7/16. I agree with the heat - don't wanna use it if I can. I was able to break free my dodge unit bearing with no problems using the 1/2" bar and cheater pipe. I'm thinking the previous owner used a torque wrench on the nut and its a lot tighter then 175ft lbs. I'm gonna buy a 3/4" drive and socket and try this next week. Thanks for the input all.

By the way, I am tearing apart my front axle this evening, and I am using one of the "more boogered" 12 pt. bolts to help remove the bearing by screwing it back in about 1/2 way, then beating on it with a hammer, then on to the next hole, and so-on. The pass. side came off in less than 3 minutes this way, instead of the usual 30-45 minutes using a chisel.

ren said:

By the way, I am tearing apart my front axle this evening, and I am using one of the "more boogered" 12 pt. bolts to help remove the bearing by screwing it back in about 1/2 way, then beating on it with a hammer, then on to the next hole, and so-on. The pass. side came off in less than 3 minutes this way, instead of the usual 30-45 minutes using a chisel.

Click to expand...

Next time you do a major brake job, paint on of the rotors either black or red (so you know it's not serviceable) and use it as a slide hammer to get the bearing assembly out - even easier that way.

If you do rear brakes first, a drum will serve just as well.

Tried that once, the stupid bearing assy. pulled apart. I think that the bearings were cooked, though. I guess that you could leave the axle nut on the hub, just hand tight to help hold it together maybe?

I had that happen once - same cause. Put a slide hammer to it, looked at the three screws and stub nut on the deck in front of my feet, said a prayer to Nimrod, and popped. Damn thing fell right apart!

At least it confirmed why I wanted to replace the hubs as well - damme if half of the bearings weren't bloody gone! Ouch...

That job turned out to be ball joints, tie rods, Pitman shaft seal, hub bearings, oil sump gasket, ...

5-90, you have a disturbing way of making me feel a certain amount of dread with this bit of P.M. I am in the middle of....

See this post for issues with getting the unit bearing assembly off the knuckle.
http://www.naxja.org/forum/showthread.php?t=910520

Later,
Joe