will a transmission from a second gen work in a first?

 

For the MTX a 2000 will bolt on because it's a cable clutch like the first gen. 2001+ are hydraulic clutches so you would need to swap out the bellhousing.

If you are referring to an ATX then the 2001-2004 trannies are a 4 speed and won't work w/o major modding and then you will have to deal with the heat problem.