The Ford Barn

dmgirardeau · 11-11-2024, 10:08 AM

I have a 1949 Ford F-1 sporting the heavy duty 4-speed (spur gear) transmission. As I prefer synchronizers in my transmission, I looked around and found a T-87D-1 (heavy duty 3-speed). The rear bearing retainer on this "new" transmission has the integrated emergency brake with rear retainer that is incompatible with cross member on the '49 F-1 frame. The main shaft is the 11.97" 10-10-10 straight spline 8J-7061 which is incompatible with my current drive shaft. In order to use the horseshoe style rear retainer and associated driveshaft bracket (with speedo gear), I was wondering if anyone could clarify the following:

- Would a 8D-7061 main shaft 10-10-6 spline work with the driveshaft bracket currently on the 4-speed transmission?
- Can the existing rear bearing retainer from the 4-speed be reused? The bolt pattern for the 4-speed rear bearing retainer matches the one on the 3-speed case.

Basically, I would like to have the ability to swap out the 4-speed with the 3-speed, but I need to make sure the parts will work. Mac VanPelt suggested I reach out to a forum to see if anyone else has tried to do a similar swap.

11-11-2024, 10:08 AM	#1
dmgirardeau Junior Member Join Date: Nov 2024 Posts: 1	Heavy Duty 3-Speed T87 Conversion I have a 1949 Ford F-1 sporting the heavy duty 4-speed (spur gear) transmission. As I prefer synchronizers in my transmission, I looked around and found a T-87D-1 (heavy duty 3-speed). The rear bearing retainer on this "new" transmission has the integrated emergency brake with rear retainer that is incompatible with cross member on the '49 F-1 frame. The main shaft is the 11.97" 10-10-10 straight spline 8J-7061 which is incompatible with my current drive shaft. In order to use the horseshoe style rear retainer and associated driveshaft bracket (with speedo gear), I was wondering if anyone could clarify the following: - Would a 8D-7061 main shaft 10-10-6 spline work with the driveshaft bracket currently on the 4-speed transmission? - Can the existing rear bearing retainer from the 4-speed be reused? The bolt pattern for the 4-speed rear bearing retainer matches the one on the 3-speed case. Basically, I would like to have the ability to swap out the 4-speed with the 3-speed, but I need to make sure the parts will work. Mac VanPelt suggested I reach out to a forum to see if anyone else has tried to do a similar swap.