Sorry I can't help, but I am keenly interested in others' input on this, as I am very close to the end of my pushrod, and I have to be careful when tightening the jam nut in such a way, to prevent the pushrod from walking out, since there are only a couple of threads left.
So, in essence, I have the same problem, only I have just enough left on the pushrod to actually function, and I have always wondered if this was common. I have already had it walk out, once. It took about 500 miles, but I certainly don't want to have to deal with that again.
Hope you get some useful input (not just for my sake).
"I can't believe I'm sitting here, completely surrounded by no beer!" -Onslow