Bill,

I agree that 27 ft/lbs should not over stress a bolt. In the structural world, we can reuse normal high strength bolts (A325) but any time an A490 (oil quenched and hardened) bolt is used, it must be discarded and replaced. They are used in high force areas and the hardening process can cause bolt failure if they are returned to service. I can't imagine that 27 ft/lbs would cause a problem unless they are VERY small bolts.

 

Interesting! I just looked that up. Found a procedure in the '09 FE Workshop Manual where it's used.

Is it a special fastner or just a special procedure? Just sounds like more of a special procedure to me. Just wonder how that's done during assembly and not by hand? The very expensive electronic computer controlled DC torque guns are problematic enough without adding a added "twist" at the end!!

This hasn't made it into Ford rearend assembly yet that I know of but I worked in the truck end. It could be used in the newer rearend assembly line for the Mustang though.

 

You are correct in the use of regular bolts with a special procedure to tighten them. The SO Tech Angle will hit a certain torque limit and then allow you to turn the fastener an additional number degrees as desired. The auto multi spindle torque guns in the assembly plants should work the same way.

 

I don't think so because they use a standard torque wrench when there's a questionable fastner. How would they quality check a SO Tech Angle bolt?

 

The Tech Angle is a torque wrench. They use a strain gauge for the torque plus an angular movement. You can see one here:

TechAngle Torque Wrench

You can also use a std torque wrench and something like this to accomplish the same thing:

Torque Angle Gauge

The bolts are just normal bolts but the tightening method has been changed to "elongate" the bolt almost (or to) the point of yielding to give the maximum clamping force on the material.

I would think they would be able to duplicate that on the line. I know they do in engine assembly and some internal tranny parts.

 

Did the work yesterday. The bolts are 5/16" by 20 tpi by 2 1/2" bolts with a T-45 torx head. They were threaded the full length of the bolt, though it was clear they only engaged ~1/2" of the threaded length. They had thread locker and a rubber(?) band type retention device along the threads about 1/4" above the thread locker.

The retention device strikes me as an assembly line feature without utility after production line installation. It did make removal of the loosened bolts a bit awkward.

I could not find a strength marking on the bolt (8.8, 10.9, etc).

The U-Joint cap straps & bolts seemed in good shape and replacing them struck me as uncalled for. Their torque was 17 ft-lbs and there was no thread locking compound on the threads apparent.

 

Yes, I found the wrench, etc. before but I'm more curious as to the equipment that does this during factory assembly. Have replaced many electical torque guns, some of which for nothing because we were at the mercy of electricians! Can't imagine these becoming more electrically complicated than they already are!

Remember one repair gun after a multi-spindle operation that would almost throw the assembly pallet off the line when it hit the its torque limit!!

 

Did the above work because I felt a vibration that should have been a brinnelled U-Joint Post (OEM U-Joints at 63k). Well after all of the above the two U-Joints had no indication of brinnelling on any post! Go figure.

On the other hand on a drive into town this morning... no vibration. Maybe they were getting ready to fail and had not become visible yet...

 

With regard to A490 & other very hard bolts that are non-reuse type bolts, I understand that the more hardening is done the more brittle a bolt becomes. If the hardening is extensive enough then the bolt could easily become a use once bolt because of brittleness.

But in the end I just don't see that in these bolts. No special torquing procedure, specified torque is low, bolt is of adequate size, just doesn't add up.

This CV type joint is designed to flex some but not much as the mid shaft support bearing appears to be sufficient to keep any angle to a minimum. The bolts did not have a bow in them at all, so I conclude they had not flexed much. Installed them with thread locker. I'll check on them periodically.

Many thanks for the discussion & thoughts.