i have a 2004 RX-8 with 112k miles. when shifting from 1st to 2nd and 3rd to 4th at high rpms it grinds before engaging. my mechanic says most likely bad synchro's and from all the reading on here that seems to be an accurate diagnosis. now i am looking into buying a used transmission with 30k miles on it. the gears and synchro's are fine but it needs a shifter fork job. my question is could i install the shifter fork from my tranny into this newer tranny to make one working transmission to put back into my car?

 

firstly the forks are inside the transmission, so unless one is broken i would question the "fork job" diagnosis, or at least wonder who the intended recipient of the fork job is, you or the transmission

second, the forks are wear items, so yours will likely be out of spec as well.

in the scheme of things the forks are not very expensive new ~$100 each, and there are 3