I recently purchased a manual 96 S10 and if I try to slow down and then speed back up while still in fifth gear, the shifter gets pushed out of 5th back into neutral. It does the same when it's in reverse. Any thoughts on why it might be doing this? It'd be a great help. Thanks

My initial reaction as to why it's popping out of gear is that it's not fully engaged. That can happen for two basic reasons, either a linkage problem or a problem with the gear/slider inside the trans.

If I understand it at least the NV3500 is (according to Haynes) a shifter that can't be serviced, but you might not have that trans unless it's a 4.3 Don't know about any of the other 5-spds.