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OC12 Pinion shaft nut torque

Snowcat Pat

Active member
OK , I want these OC12s' to last, they are not in production anymore (that I am aware of) so anything that will prolong their life is good for all of us. Lets start with this.

This is important. On most of the OC12's I have rebuilt the Input Pinion Shaft Nut is not tight, and damage has already occurred. Its easy to think it should be adjusted like you would a wheel bearing, but thats not correct. It should be very tight, I can't find it in the manual this morning but somewhere it is spec'ed to be torqued to 275 foot pounds. Not easy to get it that tight, but if it if is not the Pinion Bearing Spacer grinds down fast and the assembly gets looser and the R&P fall out of optimum alignment, all very bad. I make a wrench out of channel iron that fits over the Yoke to hold it while tightening the Nut. Its not a hard thing to make and simplifies the procedure. Don't just tighten it using the gears to hold it.

A simple in-machine test is to try to spin the Seal Spacer (behind the Yoke) with your fingers. If it will, you already have issues, but tighten it up anyway.

I'll have more questions than answers for this section usually, but I wanted to share this, and to get his section going. I also want to encourage discussion and debate (but not insults). Everything I write is IMHO. Thats all from me for now, got to get back to it.


Pat Foster
Wallace Idaho
 

Snowcat Operations

Active member
SUPER Site Supporter
If I have the correct one in mind then both of mine are very tight. Pictures would be a huge help though. Thanks Pat!
 

Mainer

Boggie likes our museum
SUPER Site Supporter
It would be a beautiful thing (tears to the eyes), if someone were to take step-by-step photos of the next diff rebuild that is done (OC12, OC15 or other). Something like how weatherby is doing for his entire end-to-end restoration of his 601.

That would be a fantastic bit of value to everyone on forums given it is the most significantly different and critical piece of kit in any snowcat...ok, barring SnOps special affection :)puke1: ) for the "diff-less" dual-shaft trackmaster. :)

:weneedpic
 

Snowcat Pat

Active member
Its in the works. I have taken dozens of photos of the rebuilds and mods I make when rebuilding, I'm taking more photos every day. But I am not a computer whiz and I don't own a digital camera. For some months Ive been working on a just such display for my web page. I thought a nice title would be "Inside the OC12". My Historic Wallace Idaho webmaster is quite busy and so am I but we will get it going in the next few months. I am unable to post photos to this site. I only have web based email, 24kbs on a 5 mile long phone wire.
Over time we can discuss here all the potential failure modes and mods that I am familiar with, but have patience. I want others folks with experience to post here too. I'm here to learn so I'm trying to instigate responses from those folks. We are also getting set to restart our business with a new name and mission.

Pat Foster
Wallace Idaho
 

Jess

Member
im bringing an old thread back to life!
is the torque still 275?
i replaced the seal and the nut was not very tight, but gears look good and no metal chunks in oil after a hard winter workin!
 
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