I have a GSR trans w/ ITR LSD and a LS 5th gear....This trans was my first repair by myself. I had to replace the destroyed OBX diff. While I had it apart I changed the gsr 5th gear to an LS. Works great, shifts like butter, I need more MPH in 4th. I have some LS hydro gears, that i robbed the 5th gears from....

Can I just swap the 4th gears? Keep all the same syncro's, hub, etc.

 

No.

 

Would i have to change the complete 3rd -4th (gears syncro hub selector ring ect)?

 

Yes you would need to change the complete 3-4 setup along with the 3-4 fork.

 

thanks james! looks like the trans has to come out yet again lol