Tom, I can't believe I'm seeing this. I have been fighting this for some time now. I'm betting you have a non-turbo 300. Thats what I have, with identical problem. Fortunately, there is a fix.

You don't say, but were your pins sheared axially? What happened in my case is that the balancer bolt works loose and allows the balancer to free wheel on the crank end. This wears the I.D of the balancer and wears and/or scores the crank end. I tried to replace the balancer (new, with pins, bolt, washers) over $200. Torqued the heck out of it (probably incorrectly, as Larry has pointed out). But probably didn't matter, as once you have wear, It wont stay long. Mine lasted a week. Also I'll bet your bolt threads are shot.

I learned of the fix from CHAPP, who had the same problem, and will probably weigh in here. ( By the way, thanks CHAPP).

Which is to have a Diesel mechanic/ Machinest redrill and repin a new wheel in place. May even add two more holes and pins, for a total of 4. It has worked well for CHAPP. Mine comes out of the shop today. Hopefully, I will have same luck. Also, a super hard paste is added, which takes out up to 10 thou. of play. Supposedly titanium paste, available from Cat. Diesel. I'll ask my mechanic where it came from. As Larry says, the alternative is crankshaft machining or replacement, both of which is obviously expensive.

E mail me if you have any more problems with it. I don't think there is any other fix, if you have wear on the crank end.

Good luck, Andy.