Proto 2000 Y3 question

[nw-modeling-list at nwhs.org]

I have three of these. Two of them run flawlessly. The third one I popped a
DCC decoder into yesterday and after programming... the front set of drivers
operates, the rear set do not. They are not jammed, because there is some
play in them. They act almost as if the motor is not connected to them. I
COULD contact LIfelike I imagine to get it replaced, but if its something as
simple as popping the shell off and finding a u-joint that is not connected
to the drivetrain of the rear set of drivers I would rather just fix it.
Advice? Anyone experienced a similar problem?

Thanks

Bob Welsh