I have seen alot of posts and have read the service bulletins on the S2K popping out of 4th. I recently found my car doing the same. I thought to myself DAMN IT now I have to go through the tranny. I just couldn't believe it. I have never had any problems with my tranny like most S2K owners have. But I guess this was the start of the "comes in threes" crap.
So I racked the car and just wanted to do a inspection of everything cause I'm Autocrossing the car alot and just wanted to check it over. After inspecting everything I found the drivers side motor mount top nut missing, WOW I thought since everything was torqued to factory specs. After replacing the nut it has not popped out of 4th gear. I thought I'd share just in case anyone has this problem just check all the mounts before you pull the tranny, it will save you alot of time and money. How that mount was causing that I don't know but like I said it hasn't popped out since. 1 week into it.

 

good job.