so i had a customer come into the shop today with complaints of a leaking Tcase output seal. this was on a later model sealed output 231

upon checking it out i noticed the seal was torn and sitting ontop of a groove in the main shaft. kind of odd. i checked through our stockpile of NP231 mainshafts that we have leftover from rebuilds and SYE's, and i didnt see this groove in any of them.

so i removed the tcase and tore it down, and then replaced it with a different mainshaft without the groove in it. and this allowed the new seal to sit on a normal seal surface on the shaft. also when tearing down the case i noticed it was a junkyard unit from 96ish casting.

anybody had this issue before? it is a machined groove that is about an inch away from the groove for the snap ring.

ive never seen this issue with a NP231 before and im just trying to figure out for my own knowledge.


some pics.
how the seal sat on the old shaft


old shaft with groove


the torn seal


new shaft without extra groove



new seal and different main shaft installed

 

I just tore down a np231 late production 96. it has the same 2 gooves in the shaft... mine was not leaking at all. took a pic 4 ya. the seal surface on mine was riding just past the second groove, but did not touch it.

 

Hmm. Wonder why it was touching on this one.