YZ450 trans swap

My buddy has a 03 yz450 with a blown out 1st gear and has a lead on a good yz426 bottom end. Are these interchangable? Other than a different piston it should be a straight forward swap right? He has never split cases or even done a top end for that matter, would it be worth looking into or just fix 450's first gear?



Fix 1st gear and the shift forks - this will be easier than a full swap

Not exactly.

The 426 5 speed can be installed in a 4 speed YZ450, but it's not a bolt-in. There is a bit of machine work involved, and it's kind of a PITA, actually.

The only trans that can be interchanged with an '03-'05 YZ450 is the trans from an '03-'06 WR450.


Likewise, the 450 top end will not fit the 426, and the 426 engine isn't a direct fit to the 450 frame. It won't be that expensive just to repair the 450.

Thanks guys, thats what I needed to know. I guess I'll tell him to get a service manual and fix it him damn self.

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