With the gas motor I really didn't have any trouble as both the threads and nuts lasted until a while after I put the diesel on, maybe 6000 hours before I had to replace the first one, with the diesel before the bronze nuts I had to replace every 4 months or so , now with the bronze nuts the first nut wore out after about 4000 hours and the rod still looks like new. One of the first things I did on the B20 was to cut a little slit in the accordion boot and lube the rod a couple of times a day with 80 - 90 gear lube through that slit. Also the bronze nut I got online wasn't self aligning like the TK was ( I don't think that self aligning worked) so I run the head up near the top where it gets hard to turn and then loosen the mounting plate for the nut and put shims under one side so it gets aligned with the rod and it turns easy. A even did that with the original TK setup which kept that running a lot smoother. These bronze nuts are available online for around $60 and they also sell a treaded nut holder for about $ 65 which fits right on the B20 except you have to drill the mounting hole a little bigger, after getting the holder it cost me $60 to replace the nut. Sure was nice to run 4 years without having to fix that. Steve