In the beginning of the summer I installed a DD Machine doubler into my YJ. It is the np 231 backed by a dana 300. I ran it for two trips without any issues. On the third trip I was stuck pretty bad in some rocks and had to get yanked out backwards. As I was getting pulled back I was easing out on the throttle and heard a pop, and suddenly had no throttle. I started leaking 90 weight fairly bad from what we believe is the back of the tranny. Upon inspection I couldn't find anything broken on the tranny or 300. I decided to hop back in the jeep shift everything around, and then suddenly I was able to drive out of the trail without anymore issues.

Well since then it has happend on every trip and seems to be happening more frequently, and everytime it pukes 90 weight from what I still believe to be the output on the tranny. Has anyone else experienced this? Is it possible that I may just be missing some sort of spring in the 231 allowing it to pop out?... but why would it be puking 90 weight from the tranny everytime it happens?

Sorry I'm lost and am desperately hoping that you guys can help me trouble shoot this.

i had the same problem and noone could tell me anything. I replaced the detent spring and ball, the shift fork, and checked everything over and couldnt put my finger on it. I finally just put a 4:1 kit in hte dana 300 and called it good. Mine would work fine till you got some torque on it like trying to climb a ledge or over a big rock and that is where you needed it. if you figure it out please let me know as I still have it sittin in the shop wondering what to do with it. Only differance is mine never puked fluid.

Thanks
Mike