Re: No input seal on a Jeep T18a?
If it has a seal it is inside the front bearing retainer,(the part the throw out bearing rides on) I bet it is in there. Very early transmissions did not use a front seal, the input shaft had a helical groove similar to a thread machined on it, this groove acted as an archemedies (SP?) screw pump, constantly forcing the leakage back into the bearing area. Later transmissions used a double lip seal inside the bearing retainer. The latest retrofit repair is to use a sealed bearing in the front and rear main shaft, this pretty much eliminates any leakage problems. I think advanced adapters has the sealed bearings. If you go to a bearing house to get these make sure you remove the seal on the oil side of the bearing, you do not want a double sealed bearing, only sealed on one side, but you probably will not find a bearing with the single seal and the snap ring groove.
good luck, jjc