axle nut

[sidekickin]

I tightened my axle nut 6 months ago with an impact wrench and it was at least 150 ft-lbs torque. Now I go to check the axle nut for tightness and it seems to have worked loose. So, how does an axle nut work loose when there is a cotter pin holding it in place? It seems impossible. What is going on here?

[Turbone]

The cone washer is wore out. And most likely the flat washer also.

[NorthWet]

Another thought is don't rely on an impact wrench to "torque" something to a specific value. That requires a torque wrench.

[edrach]

Another thought is that the round part of the CVJ that seats in the backside of the hub had dirt in the way of proper seating; as that dirt disappears, the nut appears to loosen.

[GeneralDisorder]

Even a 500 ft/lb impact will not come close to removeing the axle nuts if torqued properly. I would guess you got it to maybe 50 lbs when you installed it, and the loose wheel wore out the cone washer and made the whole assembly looser. Also they sometimes just don't go 100% tight the first time. You should get a BIG breaker bar and stand on it a couple times.

 

Impacts are not going to get the thing anywhere even close to 150 lbs. (unless you got one of those BIG 1" impacts, and an ocean of air to run it with). The impact can APPLY a force equal to a few hundred pounds of force (550 in the case of my 1/2" version), but all that torque goes straight to the sides of the nut. Think about how much force a 200 lb individual like myself can apply to that same nut with a 24" torque wrench.... it's not even in the same ballpark. NEVER use an impact for things like that. They are good for lug nuts, and not much else except loosening.

 

GD

[TomRhere]

Also, one should "Never" use an impact on bearings, they don't like it.

[daeron]

Even a 500 ft/lb impact will not come close to removeing the axle nuts if torqued properly. I would guess you got it to maybe 50 lbs when you installed it, and the loose wheel wore out the cone washer and made the whole assembly looser. Also they sometimes just don't go 100% tight the first time. You should get a BIG breaker bar and stand on it a couple times.

 

Impacts are not going to get the thing anywhere even close to 150 lbs. (unless you got one of those BIG 1" impacts, and an ocean of air to run it with). The impact can APPLY a force equal to a few hundred pounds of force (550 in the case of my 1/2" version), but all that torque goes straight to the sides of the nut. Think about how much force a 200 lb individual like myself can apply to that same nut with a 24" torque wrench.... it's not even in the same ballpark. NEVER use an impact for things like that. They are good for lug nuts, and not much else except loosening.

 

GD

 

 

I must disagree with you on this, General.

 

Youre right about torqueing things down properly, but your IR 2135 that says it torques down to 600 ft-lbs does in fact achieve a maximum of 600 ft-lbs on a bolt... as you said, WHEN properly supplied with air (almost never.) I worked rebuilding those things for some time, and we had a hydraulic gauge i used to test them with.. it registered immediately how tight this 1 7/8" nut was on a gauge, and if you fully wail on it, (full trigger, no valve tapering the flow down, with a proper 1/2 inch air flow, no 3/8,) for a good ten or fifteen seconds, it will achieve that torque.

 

now, im not saying that it should be used for such.. quite the contrary, those tools are designed to achieve max torque in reverse. They are designed and built, and should be used, for REMOVING high torque or unnaturally tight nuts. the best way they can be used in re assembly is as a shortcut, with a torqu wrench used to properly wrench it down to final specification. There is no way to "control" or "pre-set" the torque output of any gun, because that output is a factor of the volume of air supplied, and the pressure at which it is supplied. in any real air compressor system, both of those factors change in a manner that is non-linear in respect to each other, so there is no constant setting that will reach your goal..

 

and beside, as you said, it only takes 200 lbs of force times a 3 foot cheater bar to achieve that same 600 lbs of torque, AND 600 lbs is about 3 times what anything on a car should be tightened to, EVER..

 

so in other words, your impact gun is made to take your lugnuts/flywheel bolts/axle nuts OFF.... and if you use one to put them back on then only use it until it snugs down. then stop, and use a torque wrench with cheater bar, if needs be, to get your 40, 70, 100, 150 ft-lbs of torque.

[GeneralDisorder]

Yeah - I agree with that. My information has always shown the impacts to be WAY more effiecient in reverse, so I've never put much faith in their tightening ability. But then my air source isn't as good as it could be either.

 

GD