[JM 35 Sedan]

Originally Posted by rotorwrench

The 78 case was developed in 1937 but the pre-1939 units had the early synchonizer set up. The guts out of a 1939 or later transmission will fit the earlier cases depending on the main shaft type but there is the mater of the shift tower and the 91A type shift fork that has to be observed for use of the late type synchro. The double detent shift tower was the better of the top shift transmissions up though 1951 or so.

The pickups after 1941 were open drive so they have a slip yoke type main shaft and some truck like gears but the cases are good to go. The side shift car transmissions after 1939 had the wrong case but they had gears that will fit. The rear bearing retainers just bolt on so they can be traded from one type to the other depending on application. The early shift towers are tricky if a person wants to put late gears in one of the 1932 to 1935 cars that have that type of shift tower. A 91A shift fork is not a direct fit to them.

Mac VanPelt's book is invaluable for overhaul of the old Ford light duty 3-speeds. What ever questions a person has that the book doesn't cover are only a phone call away.

Even though my early 1951 Mercury cars have the overdrive version of the light duty 3-speed, there are still a lot of interchangeable parts between them all.

rotorwrench, I've underlined two of your above statements that at one time I would have totally agreed with, but........
Last year I rebuilt the transmission and rear in my mostly original '35 fordor slant back sedan before driving this car to Auburn Indiana for the EFV-8 Club's Central National Meet. The transmission didn't really need rebuilding, but I've always wanted to upgrade to the later style '39-'48 synchronizers, and change the 1st & 2nd gear ratios to give better acceleration with 3.54:1 rear gears when starting off from a from a dead stop. To accomplish this I used a 29 tooth cluster gear and 15 tooth input gear in my original 48-7006, '35-'36 transmission case. Now instead of using a '39 shifter top with the 3" wide, 91A, 2nd/3rd shift fork, I decided to use a special set of shift forks, made for me by a friend who is very clever at design engineering and making things to upgrade these early Fords. These specially made forks fit into the stock '35 shifter top and will shift the later style synchronized gears perfectly,....thus keeping the interior appearance of the shifter top, shift lever, and sheet metal transmission cover looking totally stock. I've driven this car approximately 2,000 miles since making this change and the transmission shifts so much better now than it did previously....plus it completely eliminated the problem of jumping out of second gear, and no more "raking or grinding" of gears when shifting from 2nd to 3rd.