A few questions for the collective genius that is this list. I put an L28 into my 240z and utilized the 4-speed tranny and clutch components that were with the L24 that I removed. Didn't make any component changes or part changes or anything like that to the tranny/clutch assembly....simply bolted them up to the new L28. We thought we did everything right...clutch plate facing the right direction...all of that good stuff. The tranny shifted fine when the car wasn't running but once it was fired up it wouldn't go into gear.

I'm not much of a tranny/clutch expert at all. In fact, I'm pretty much clueless on that front. That said, I know from the list that you usually want to keep the original components of the tranny/clutch when swapping out the L24 for an L28 so that's what I did. We now have the engine and tranny back out of the car and are preparing to try to fix the issue. Anyone have any ideas as to what may be the problem? Like I said, I'm no expert in this area so any advice you guys can provide would be greatly appreciated.

Thanks in advance.

You probably did not replace the throwout collar. The throwout collar matches the pressure plate, not the transmission. Get a throwout collar for a 280z and you'll be fine.