Thanks guys, I didn't expect this many replies so fast. After posting, I went to the barn (no internet) to continue taking parts of an M715 I recently acquired that I plan on restoring. I have comments for everyones replies, first one first:
NDT- Pulling it and taking it to Hou Trk parts was my plan B. As is, it is still useable, and I had added an air conditioning unit that sits right under the dash where the valve is, making access a pain.
155mm- O Ring is probably right thing to do and cheapest, if I can find a replacement O Ring. May be getting back with you on how to.
doghead- the part target url you gave me threw me off at first. I had found that to in my search but ignored it because only the last 7 digits of the NSN were the same. But looking down the list, the 1073 part number is there.
Simp5782- You said part number was KN 20021, it should be KN 20022, doghead posted.
Again, thanks to all of you for putting in the effort to help. I plan on going to Houston Truck Parts on Tues to see what they can come up with for a Haldex KN 20022. I will follow up with post if I find another part or if I have issues with it.