Look here to see if there is a parts manual for your model. If you don't know what model it is, you might have to slog through a few to see if anything looks familiar, or, if you have the bad seal out, take it to a bearing supply house and they can match it. It's probably a very common and inexpensive National Seal #.
Ingersoll 448 with 42" tiller and 60" deck. John Deere 3046R, cab, T&T, H165 loader with 4and1, 60D Autoconnect, 72" boxblade, 59" snowblower
Just finished rebuild of Troy Bilt horse. Partstree.com was able to supply everything that I needed. They have exploded views, but are kind of difficult to read. BrentChalmers.com should have technical and owners manuals. Good luck.
When my Pony started to leak I got new seals and took them all apart. Found out that the seals were fine on it and that it was some metal "chuff" and filings that had got under the seal and lifted up the rubber from the axle to allow the gear oil to leak out. I just wiped them off and reused the old seals and they never have leaked anymore. Remember when you re-fill the transmission you'll need gear lube compatable with "yellow" gears. The gears are bronze I think so the multi-viscosoty gear lube is out. I have a bottle of 130 wt left over from my Pony days if your interested in it private message me.