Hello,
I am going to swap a 3spd standard transmission for a manual 3 spd with overdrive. The engine is a '56 272 truck engine. I am told that I need to find a tranny with the right input shaft splines since the car tranny and the truck tranny used different input shafts. Does anybody know the number of splines and diameter that is correct for my application?

Also, I am told that I could bolt the OD section from an OD tranny from many manufacturer's autos (chevy, studebaker, etc.) onto my standard 3 spd. Does anybody know if a cross reference or a list exists somewhere that specifies which cars/trucks and which years are candidates for either using the OD section with my tranny, or swapping out the entire tranny altogether with minimal fuss. Any advice on this topic is greatly appreciated.
Thanks,
Jeff Moore

 

This is coplicated by two things: The 54 through 56 trannys have a boss for the clutch pedal shaft, so you can't use a 3 sp w/OD from trucks up through '63. Secondly, some 3 sp if they were the medium duty 3 sp will allow the BW OD to bolt up. The OD tranny was a Borg Warner T-85, and the 3 sp as used with v-8s will allow the OD to bolt up. Also, the 56 and later are 12V, so that means the solenoid must be a 6V for your '55. You can use the Ford passenger car OD unit to bolt on to the B-W 3 sp. They seem to be a lot easier to find.

The truck used a 1 3/8" main shaft which is a lot larger than the 1 1/16" shaft on the passenger car. Also, the bearing retainer is a lot larger for a larger throwout bearing, and the truck case has to have the boss for the clutch pedal shaft, so adapting the wrong case is not a good option.

Besides the OD tranny, you need a manual lockout cable, a kickdown switch, and an OD relay, a wire each to the governor and the solenoid, and two wires to the kickdown switch.

It is a good way to go, but you will need to acquaint yourself with the transmissions, and the overdrive electrical.

Regards,

Alanco

 

Hello Alanco,
Thank you very much for the information. This is very helpful.
Jeff

 

I did what you are talking about, I found a '51 Merc 3 speed OD and wanted to put it into my '53 F-100. The car input is smaller as our other member said, but the inside ie the 16 tooth and inside bearing surface are the same from the car and light duty truck 3 speed. I did the following changes: I swapped in the truck input shaft from my original trandmission, the truck shift side plate because the '53 clutch shaft linkage bolts to the side cover, and made sure that the anti-reverse rod can go through the adapter and 3 speed case to 'lock out' the overdrive when you shift to reverse. If you do this, you can use the original clutch and related, just remember that you will need the driveshaft cut down by someone that can re-balance the shaft. These OD units have a fill and drain plug of their own, the fluid can flow to the 3 speed as well, but the fluid opening in the cases is too high, so if the OD becomes low of fluid because of tailshaft seal wear, the centrline of the OD moving parts starve for lubrication and usually the sun gear grenades! Cheers.

 

Good Job!

Regards,
Alanco

 

This is all excellent advice. I am finding ot very useful in searching for the right parts. Thank you very much for the effort guys.
Jeff