mongolchuck

OK finally had some time to reassemble the valve body on my aod and replace the reverse servo. It was a one groove servo that had been replaced before based on the 2011 date on it. Got it all slapped together with a cooler from a 98 grand Cherokee (perfect size) and still no reverse. Doesn't even try.
So here is what I'm thinking. There was very little in the pan or on the magnet the first time I took it apart. Fluid was clean, no metal flakes and again only a tiny amount of black material. I don't think its a band or the reverse clutches. The servo went in pretty easy so I'm beginning to think the rebuilder just grabbed a one groove servo when he needed a 2 or 3 groove. Am I off base? Is there a good way to measure the pin length needed or is the bore a little different?
I hate just throwing parts at something but a 10 dollar servo is pretty cheap and I'd much rather try a 2 groove than rip the trans back out and tear it down.
Thoughts?