ok im wondering if its been done, i have the jdm l3 trans that came on the non-lsd zc trans, the diff pin snapped and messed only the trans housing up gears untouched and i have a us si l3 with a blown 3 gear can i put the zc guts in the us housing ?

 

Yes you can, in fact it will give you a slightly closer gear ratio if you use it with the final drive set from the US Si transmission. If you want you can use the ZC 1st-4th gears and leave in the US Si 5th gear. This combo will have a slightly lower cruising RPM for highway (it's not that much lower but it helps a little...very little).

Note: Info above is assuming you have the JDM DOHC ZC transmission