My wheels could be fixed by spreading 3 sets of them apart, one set was ok. Weights could be added to get them to NMRA standards. Not sure how the couplers could be fixed, I have never attempted coupler maintenance, so don't know a lot about that, but these are pretty lightweight.
Should have previously added that they all appear to be plastic and no matter what you do they are still plastic. Only thing magnetic on the trucks were the axels and the un-coupler shoe (button or what ever they are called).
I don't have the issue with plastic trucks other have IF THEY WORK WELL. I weight my cars (mostly Weaver) to standard or more and find that I can't tell if they have die cast metal or plastic trucks.
As for couplers... if mine act up I close them, add a few drops of epoxy to the mechanism and they are fixed forever!!!! Really....how many of us do extensive switching operations??? I don't even own a un-coupler track and none will be on my layout. I like to RUN trains......
I'd be willing to pay shipping if any one wants to send me a set......I'd like to see if a fix can be devised and applied so they don't have to be replaced on all of them.
I added weights to NMRA std. when I got the car out a couple months ago and it didn't run well. Might try spreading the 3 wheel sets to the proper gauge to match the one that is correct. Also, I seem to have locked the couplers shut somehow, couldn't open them earlier today and I haven't glued them yet either? Mine never came open even pulling 10-12 or so MTH RailKing cars. I had trouble getting them to close...musta done a good job on that one. 
I only have the one car and my grandson likes the tank even if the car doesn't run just right, so I will probably keep it for a while for him to play with. I think I may also have some Lionel or MTH metal trucks around here somewhere, maybe I will give it the Pine Creek RR treatment if he wants to run it often.
