I have a narrow brake drum (3311) with removable clutch shoes like the 26-27 has. It has the groove on the back for an early trans. driving plate (3321). Here is the problem: the brake drum has the same bolt circle as the 26-27 driving plate (3321B). If I use this there will be a gap where the groove is on the brake drum. The pre 26 driving plate fills the groove but the bolt circle is off by approx. 1/8". I could enlarge the holes but I am sure that is not what they did originally. Does anyone know how this was done when they were produced?
I think what you have is a wide brake drum that has been cut down. I have seen a number of them done that way but it is not the best possible way to go. Care must be taken to ensure that the drum and driven plate are concentric.
That is a late 25 brake drum. If my rememberer is right, Ford was possibly experimenting with the ne design before they brought out the large brake drum. It has a special driven plate that will only fit that brake drum.
Could be a cut down 26/27 wide brake drum or a late 25 as stated above.
So I have a question, didn't the late 25 also have the flange that slip over the drum?
Elongating the holes of an early drive plate is just wrong. It has been done but not the best approach. IMO
I have used that late '25 style drum with the replaceable shoes a few years ago. The drum is for the shoes, used in late '25. The driving plate is, if I recall (that is scary, as I don't remember for sure), made for only this late brake drum?
Normal small drum and driving plate on left....small picture on right is the late '25 drum with replaceable shoes and driving plate. The screw bosses are higher on this plate, as compared to the bosses for the normal small drum driving plate. And slotted screws used to fasten.
Ford recommended filing the holes, it's outlined in the March 1927 service bulletin. Page 470 of the service bulletins book.
Thanks for the straight scoop.
A cut down 26-27 brake drum would still use the 26-27 drive plate.
Ken That is very interesting. Looks like March of 27. Wonder just how long that change lasted because it really is not good engineering!
RE Ken's photo
By that time in 1927 work was under way or started on the New Model A, so maybe it was just a stop gap fix.
Brendan, There IS a specific driving plate that will fit these drums.
However, filing out the holes of a pre-1925 driving plate as is mentioned in the service bulletin is just fine because the end of the transmission shaft pilots to the driving plate to insure alignment is correct when it is assembled to the drum.
I've got a couple of these narrow trans drums with the lugs and have always been on the lookout for a correct drive plate, but didn't see one for the first time until a friend of mine brought a trans over a couple months ago to be disassembled. It had the narrow drum with lugs AND the correct driving plate with correct bolt holes...
I've filed the holes on an earlier driving plate to mate up with a 25 brake drum. If you're careful, you can get a good job. Its slow tedious work, but worth it if you get a close fit.