1250 hydro replacement
 

I'm going to be pulling my hydro in my 1250 and swap in a replacement. Do I need to pull the transaxle to remove it or do I do it all in place? Also what is the best way to thoroughly clean everything without getting any water or other contaminates into the hydro or transaxle?

In place is just fine.

It is MUCH easier to replace the hydro unit with the transaxle out of the frame of the tractor, plus it is easier to properly clean everything. To clean, use a spray degreaser and low pressure hose water to rinse. Pressure washers will force water in seals. Don't forget the cork gasket from the hydro to transaxle.

I have done it both ways. In the future I will always pull the transaxle out of the frame. Doing the work with the transaxle in the frame took more time and effort than pulling the whole thing out.