I have a 15 Roadster that has been modified with a starter. The engine is a early 15 by serial number Jan of 15. Trying to determine what has been changed when the modification was made. How do I tell which transmission is in it?
The transmission has nothing to do with the flywheel, except that it is bolted to it. It obviously has a starter flywheel, but still could have the '15 transmission.
I can't answer your question directly but if all that was done was to add the starter, then in all probability the flywheel, mag ring and hogs head were all that was changed. There would have been no need to change the transmission unless something was wrong with it.
Unless you were there when the transmission was swapped out there is no way to tell from the outside. Any differences are internal. You could pull the hogs head or even look through the cover and would still not be able to tell unless it was a modified 26/27 setup.
I's much easier to put a newer flywheel with transmission in place as a unit, so if they had access to a good trans with flywheel it's possible it was swapped. But if the transmission was restored in the process, then maybe the original parts were used.
If you need to pull it apart in the future you can check the flange of the transmission main shaft - it was dated on all Model T transmissions up until early 1915. The brake drum bronze bushing has a flange on early transmissions up through 1915 - the three steel washers came after. And there's a thick distance plate under the clutch discs inside the brake drum.
Maybe it's possible to tell the difference between pre starter style riveted triple gears from the inspection lid? The riveted triple gears has wider teeth compared to the later style, so if you can see a triple gear like this through the limited view through the lid, then it wasn't the transmission that came with the starter flywheel that was used in your car - unless it was a Canadian transmission of course, they used the riveted triple gears much longer than in USA..
Pre starter riveted triple gears in this trans:
(photo by Royce)
Post WW1 triple gears with distance between narrower teeth here:
(Picture by Dan Treace)
Thanks to every one for the information
An additional external indicator will be the clutch finger adjusting screws. A 15 having a distance plate, 13 small and 13 large disks total of 27 pcs will keep the adjusting finger screws at least 1/4 - 3/8 above the driving plate where the cotter pin goes through. On models where the distance plate was discontinued (mid 16) and one small disk was removed will lower the adjusting screws to near flush with the driving plate.