If the PTO is like my 1955, check out the linkage in the cup in the back that the linkage rod from the cab connects to. The linkage inside that may be worn badly and have enough play that it won't allow the PTO to shut off properly. Mine is worn badly enough that if I get it to engage properly, it won't engage the brake upon shutoff. For the time being I just get out of the cab and push down on the rod until the brake engages. Another winter repair project.  <!-- s:wink: --><img src="{SMILIES_PATH}/icon_wink.gif" alt=":wink:" title="Wink" /><!-- s:wink: --> I had to rebuild the clutches in my PTO assembly and it set me back $1,200, including labor. I have also seen rebuilt 55 series PTO units advertised. It's been  a year or two but I believe the price was right around $1,200 plus your unit in exchange.

Oh and a 1755 is a nice tractor. Very nice steering, good hydraulics. Pretty decent brakes. Good workhorse tractor.