Can I use a riding lawnmover differential for a buggy or will the gearing not be right?

Thats a good idea and question. Are you thinking of using one you can shift on the fly, or the old style that you cannot shift while in motion?

I honestly dont know, Im buggy challenged, trying to learn.

I grabbed the lawnmover out of the trash around a year ago to build my kids a go kart, never happened, we bought a Dune instead. I happened to have stumbled on a 350 Honda with reverse so I got the idea of building a kart for myself.

I started stripping the lawnmower today of anything I though I could use in the future, the motor is trashed. I grabbed the starter, carb ETC.

I then remembered I pulled the rear out of it and stored it. I got it out today. I put the axle carrier on jackstands and spun one tire, the other tire spins after 1/2 a revolution, does that mean its a limited slip?

Im not sure what you mean by shifting, the diff I have looks just like a car one except smaller and that instead of a drive shaft it has a pulley on top of the axle carrier. I thought it would be cool to use it in a buggy but like I said in my original post, the gearing concerns me.

The old style lawn tractor transmisions were a basic 3 forward gears and reverse. The newer style shift while in motion I think. Both of mine are hydrostatic drive so its just push with the foot and go.
If you have a Honda motor with reverse, then why are you thinking of coupling it to a lawntractor tranny?

I have a lawnmower rear differential that I thought I could connect the Honda to. I figured I be better off with an actual differential in the rear than just a straight shaft.

I *think* most riders are regular open differential--in order to be most kind to your nice lawn
Given the choice I'd take the solid axle over an open diff. I like mud and need both tires churning.