[layback40]

After doing a bit of detective work I have the following information that will be useful when it comes time to replace the seal like I have today.
For a NP 231 transfer box.
Housing bore 2.376"
Seal OD 2.383"
Width .42"
Shaft Diameter 1.503"
It appears that the original seal was a Timkin 4307N
My local bearing shop had no listing on it.
After market Amix Ada 1867.29
another number was 4638904
In the end they had 2 choices;
KOK K606 HTB5YL 38.1 60.35 20.7
This is a seal that looks like a slip yoke seal, it has a large dust seal & is the one that I have fitted.

alt;
CR 15004
This is a standard oil seal & would probably do the job. The sort of seal most bearing places stock all the time. If you were stuck in the bush & needed a quick fix to continue your journey this would be fine.

Edit; Probably a 401670N would also fit. Its 1-1/2X2-3/8X3/8

Less than 1hr to do the change. Use silicone to seal in the housing.