Hi,
I have a Proto 2000 GP7 (HO Scale) which has developed a thump in one of the trucks. I have checked the wheel gauge and taken the wheels off to check them, and everything seems normal. When the engine is run at crawl speed (both in forward and reverse), you can see one corner of the truck lift up a fraction of an inch every 6-8 inches along the track. The condition is worse when hauling a load of 7-8 cars, especially going up grades and on curves. Surprisingly, when going downgrade on straight track there is no problem.
Can anyone tell me what might be causing this and, more importantly, can anyone tell me what I can do to repair it?
-- Roy