trans issues, it broke.!!! Options

[orangecrate]

72 4 popper. 1.7 What would cause the pin in the in the tailshaft linkage to shear??? It has a u shaped recepticle on the outside that links it to the linkage going fwd and on the inside there is a finger of sorts that is pinned to the shaft that operates the internal shift rods. That pin shears. What could be hanging up with enough resistance to cause this pin to shear??? I'm stumped. I's happened twice now.
I've gone thru the trans and replaced 1-3 syncro rings and dog teeth ,1-R gear and all 4 shaft bearings. I've adjusted the internal linkage with a shaft template holder. Now it shifts really hard and I don't want to shear the pin again. It leaves you by the side of the road with a tow being the only recourse.
Has anyone messed with the detent springs in an effort to make it shift easier???
!st time a guy pulled out in front of me on the hiwy and I downshifted to 4th. When I went back to 5th there was nothing. I was in neutral it seemed. No apparent internal damage but the sheared pin!! 2nd time I was back from playing on a local twisty. Pulled up to a stop sign , took off ,hit 2nd , same thing . Nothing . no grinding no noise . Vroom vroomm no go. Pulled it apart again and did all the aforementioned stuff but found no internal damage other than syncro and dog teeth wear. and a sheared pin!!! What should I be looking for this time??? (IMG:style_emoticons/default/headbang.gif) (IMG:style_emoticons/default/confused24.gif)