Originally Posted by AntonLargiader
Is the 991 gear really NLA? I'll check this coming week. If it is, then if you want to consider '86 another break point then go for it.
I was thinking about a different coupler change ('87-on) and forgetting about the shaft splines. The '87-on 39.5mm coupler is the fat one. Not sure if I have any of the '85-'86 37mm ones around but I think you are talking about the pre-'85 ones breaking.
I don't have the years memorized. Our boxes are so old it really doesn't matter anymore. I just tell by looking into them. Who knows what your going to find inside. Pre-'85? I mean the smaller cush drive. The ones that break on a semi-regular basis. The bigger modified ones won't fit on the earlier shaft for different splines however they did make a few later PFA gears for the earlier shaft. I think those are NLA.
At Rob: I think I have seen the earlier cush drive setup break more than I have seen them wear. I have also seen them wear and have nothing to do with cheap oil or infrequent oil changes. I think some of them tend to wear for their heat treatment being a bit off. IF anything.