Originally posted by Just_Blue:
why not? Essentially I'd be buying a manual transimission, some little parts to make the in cabin area look nice. Some linkage parts for the clutch, and there I'd get some 10% improved drivetrain efficiency, and it'd make the truck better.
Don't bank on it - you probably need a new driveshaft, some mounting brackets, don't forget the hydraulic system for the clutch.... the parts list could be quite extensive. And I do believe the ECU is different for the manual tranny. Not sure on the Xterra, but on other vehicles I owned, the engines were different too (not enough to be a show stopper but made the ECU swap that much more complicated).
If you are really serious about doing the swap, you might want to start by getting a factory service manual and comparing drivetrains. Search around in the backyard mechanic forum for links to getting it online.
but as was pointed out, it probably isn't worth the cost or hassle to swap - depends. If the X isn't your primary vehicle and you can do all the work yourself, then it may be a wash and an interesting exercise. I personally wouldn't want to do it, but that's just me.