I have an SR20DET (1998 S13 Blacktop) and it developed a 4th gear popout.
It started after I completed my engine rebuild. As part of the rebuild, the things I did that affect the tranny are:
- Installed Cusco motor mounts (no tranny mount)
- Resurfaced flywheel
- New SPEC Stage 2 segmented clutch and pressure plate
- New throwout bearing
- New Pilot bearing
- New Clutch slave cylinder
- New Circuit Sport V2 shifter with solid bushings
- Redline MT90 fluid
It actually feels a bit different than other gears. It doesn't quite "pop" into place. As if the detent ball is not functioning. The shifter also slides around in 4th. I can feel it move back when I accelerate, and forwards when I lift. 3rd gear functions normally.
I've tried driving with the shift rubber boot off and it feels the same.
I did a bit of research and everybody blames it on synchros or the shaft bearings, but I don't see how that would be possible. I think that the detent on the shift fork might be gunked up or something, preventing the detent ball from holding the fork in place.
Does anybody have any experience with this?