CV Axle Nut torque Issue

[mmklaxer]

I’m ready to final torque/angle of turn the rear axle nuts, and I’m struggling to hold the rotors from spinning for the 45 angle turn. Brakes are bled and the pedal feels pretty firm (no real frame of reference). Bled the brakes a few times and had no bubbles coming out.

I’m going to try bleeding again just to see if any trapped bubbles come out, but otherwise not sure what else I should do.

The manual states to engage the e-brake to hold the rotor. I had an assistant stand on the brake pedal. Hit the 98 ft lbs, but almost immediately after the rotor starts to spin. I’m nowhere near the 45 degrees.

It’s cold in the garage here - right around freezing. I’m not sure if that plays a part on the brake system or the pads/rotors.

Thoughts?

[rich grsc]

Wedge a long braker bar between the wheel studs.

[mmklaxer]

Awesome, thanks. Didn’t know if that would bend the studs. Didn’t think so, but didn’t want to learn the hard way at this point!

[460.465USMC]

I waited until I had the wheels on and the chassis weight on the wheels. I had trouble getting the additional 45 deg. My SnapOn 1/2" drive breaker bar was starting to bend. I called it good at that point.

[mmklaxer]

I waited until I had the wheels on and the chassis weight on the wheels. I had trouble getting the additional 45 deg. My SnapOn 1/2" drive breaker bar was starting to bend. I called it good at that point.

This is good to hear. the breaker bar idea got some good movement, but I was really leaning into it. I consider myself to be pretty fit, so if I can't get anymore, I think it's good to go. I torque striped the nut just for my own sanity (probably adds 0 value) but that thing is rock solid.

[Ted G]

Yes, it was impossible for me to get to 45 deg. I got maybe another 15

[mladen]

For us newbies, can anyone say why the front axle is torqued to a specific spec and the rear is to +45 degrees? Just curious

[rich grsc]

Because the fronts just go roundy round, while the rears provide all the hp and torque to the road

[mladen]

I get that. What I meant was more around instead of saying torque to eg 150 ft lb and then add 45 degrees, just say torque to eg 200 ft lb. What makes the latter not appropriate, or different.

[J R Jones]

I’m ready to final torque/angle of turn the rear axle nuts, and I’m struggling to hold the rotors from spinning for the 45 angle turn. Brakes are bled and the pedal feels pretty firm (no real frame of reference). Bled the brakes a few times and had no bubbles coming out.

I’m going to try bleeding again just to see if any trapped bubbles come out, but otherwise not sure what else I should do.

The manual states to engage the e-brake to hold the rotor. I had an assistant stand on the brake pedal. Hit the 98 ft lbs, but almost immediately after the rotor starts to spin. I’m nowhere near the 45 degrees.

It’s cold in the garage here - right around freezing. I’m not sure if that plays a part on the brake system or the pads/rotors.

Thoughts?

MMK, I am not a roadster guy so I am not familiar with specs on your application.
Many years ago engineering found an accurate method of torquing called "torque and turn". It involves a small torque to seat the parts and turn to a specific angle that stretches the bolt, mostly in the threads. The stretch could be called a spring load to keep the joint tight. 98 lb ft is not that much, typical for lug nuts. Block the axle or brake, or install the tire/wheel and block the car with chocks or put the transmission in gear.
jim

[CraigS]

I have always hated TQ + angle. Once I was told that TQ wrenches are usually out of spec by a % so they are further off the higher you go. So start w/ a low TQ value and ad angle. I have to say though that working as a dealer tech doing that, we all estimated the angle. It was good the spec was usually something like 45 or 90 deg since that is somewhat easy to eyeball. Personally, I'd much prefer one TQ spec and done. The other thing I don't like is I had to either mark the bolts (doing a head for instance) or put a quick diagram of the bolts so I could X them off as I went. Doing the angle it wasn't obvious by wrench feel if I was on the first 90deg or had already done the first on that bolt.

[Hoooper]

TQ+angle is usually used for stretch bolts or to deform the nut so it doesnt come off. Ironically in this case, the 2015+ mustang rear hub is known to come loose internally so proper torque and angle on it still may not keep it tight

[J R Jones]

I have always hated TQ + angle. Once I was told that TQ wrenches are usually out of spec by a % so they are further off the higher you go. So start w/ a low TQ value and ad angle. I have to say though that working as a dealer tech doing that, we all estimated the angle. It was good the spec was usually something like 45 or 90 deg since that is somewhat easy to eyeball. Personally, I'd much prefer one TQ spec and done. The other thing I don't like is I had to either mark the bolts (doing a head for instance) or put a quick diagram of the bolts so I could X them off as I went. Doing the angle it wasn't obvious by wrench feel if I was on the first 90deg or had already done the first on that bolt.

My career was in development and racing so we were typically ahead of specifications or on our own, referencing fastener charts. In torque wrenches, needle and dials were cumbersome to watch at high torque values. Clickers and beepers were much better, I was at Mercury Marine when torque and turn was promoted, It was more reliable on assembly lines, where repetition and wrench reliability were issues.
To your reference to "wrench feel", repetition lead to my muscle memory of how bolt stretch feels, and I can hit the numbers before measuring torque. Of course the sensation of going too far is apparent before the "snap".
jim

[rich grsc]

I get that. What I meant was more around instead of saying torque to eg 150 ft lb and then add 45 degrees, just say torque to eg 200 ft lb. What makes the latter not appropriate, or different.
I realize that my answer doesn't really explain what you wanted to know. It has to do with the "torque to yield" method of tightening bolts. I don't understand why it was changed, maybe something to do with computer controlled assembly?

[Hoooper]

Bolt/stud stretch using torque angle is not affected by variations in friction. Stretch resulting from static torque readings can vary drastically due to friction so torqueing to 200 ft lbs could mean a very different amount of clamping force if the stud had oil on it vs if the stud had a bit of grit or rust on it. They start with torqueing to a lower level because at lower torque values the friction error is much smaller, so you can fairly consistently be at the right "base" torque, and then use angle to get an accurate stretch from there.

[JohnK]

I'm sure that Ford, like most manufacturers in any industry nowadays, uses SPC (statistical process control) to constantly assess manufacturing processes and defects. The likely answer is that their data analysis showed that torque + angle somehow resulted in a more repeatable process with fewer defects.

As to why the fronts spindle nuts aren't specified the same way... well, the simple answer is that they are designed by FFR, so FFR specifies the torque spec for those, not Ford.

[CraigS]

JR and Hooper your experiences are very good info. JR, I guess I am young enough (I don't say that often at 74) that I have seen beam and dial TQ wrenches but have never owned one. The only time I used one it was a friends and that one experience told me no way in hell. Too difficult to read that dial. Hooper, your thoughts on friction make a lot of sense. I am aware of how that works and always use at least a little oil. I have also saved a generic chart for TQ specs by bolt dimension and I was sure to save one that had 3 columns for various types of lubes.