Mark, when i bought my 108, it had a type A pto(thrust button) and a type B brake shoe and rockshaft on it. Like Lew says, there are 2 different rockshafts for the 2 pto styles. The difference between the 2 rockshafts is the hole where the wear button would go on a type A is not flush with the shaft on a type B rockshaft. It's recessed slightly. I purchased a type A rockshaft, but i couldn't get my old rockshaft out, the sleeve on one side of the rockshaft would not budge. I starting damaging the shaft, i didn't want to mow with a push mower, so i put a couple of washers behind a wear button and used the rockshaft i had. It worked fine, I used it for most of last season to mow. I don't recommend you do it, just relaying my experience. The problem with that set up would be if you didn't keep an eye on the wear button on the rockshaft, and it wore down a lot, there's potential for the rockshaft arm to make direct contact with the pto sooner than if you had the proper rockshaft. It was much safer than using a brake shoe to stop a type A PTO, i was pretty PO'd when i discovered that. I rebuilt my PTO with the brake disc a couple of months ago, and i replaced the wear button on the rockshaft with a brake shoe, so my PTO is a legit type B again. Only got to use it once so far, seems to work fine. Just my
