"torque prevailing design" ?

[LINLIN]

I'm planning on replacing the upper control arms and wheel knuckes on my 2001 LS this weekend (bad ball joints). I was reading thru the procedure on the technical service publication CD and it seems that every bolt and nut I need to remove needs to be discared and replaced because it is of "torque prevailing design". I've never ran accross this before and was wondering if someone knew what that is all about. In the past, the only bolts I have never reused were cylinder head bolts. Looks like I'm going to have to drop some more $$ for all the nuts and bolt I need.

 

[SoonerLS]

I've not heard that terminology, but it does sound like head bolts. I've always heard them referred to as "torque-to-yield" bolts, though, meaning that when they're properly torqued, they're slightly stretched, and cannot be reused (well, not safely, anyway). It does make sense in suspension use though, as those are serious load-bearing parts.

 

[beaups]

I've heard this about the locking nuts but not the bolts. specifically what bolts are they saying this about?

 

[Macoffutt]

At work we sometimes have to use "Prevailing Torque" when we replace an aircraft component. the definition is actualy in one of our Technical Orders. but I dont have access to that right now so heres a definition from elsewhere:


http://www.boltscience.com/pages/torque4.htm
The prevailing torque is the torque required to run a nut down a thread before engagement with the joint surface. This resistance can be provided by a nylon insert or a distorted thread profile. A prevailing torque can significantly affect the amount of preload provided by the fastener for a given tightening torque
- Dont really like how that is explained so when I get ahold of that Technical Order, Ill repost if you'd like-

 

[mharrison]

Well, there you have it. It sounds like they either use nylock nuts, or distorted threads on the bolts.

Either way it looks like one or the other will need to be replaced.