Might be some help.
http://www.hoseeker.org/assemblyexplosionAthearn/Assembly%20Explosion%20Athearn%20U28%2030%2033B%201975.jpg
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Try http://www.horizonhobby.com/New/ . They are the distributors for Athearn.
Hoseeker.net (.org now?) has just about every diagram, parts list, or any other old paper work you can think of.
Here are the U28/30/33B diagrams from '71 and '75:http://www.hoseeker.org/assemblyexplosionAthearn/Assembly%20Explosion%20Athearn%20U28%2030%2033B%201971.jpghttp://www.hoseeker.org/assemblyexplosionAthearn/Assembly%20Explosion%20Athearn%20U28%2030%2033B%201975.jpg
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Rich, thanks for the link. I contacted Athearn directly and they sent me the same parts break down. I am looking for a generation before that one, it did not have the flywheel drive or the square, brass bearings on the drive axles. Thanks again for your help. I am afraid I am going to have to purchase a replacement chassis. Paul.
Darth, thanks so much for your help. The '71 model is what I have, now I just have to locate the axles or truck. It is amazing the information out there, just a matter of finding who has what information. Thanks again, Paul.