Closed drive shaft

Randy1944

Randy1944

Senior Member
I have a 1939 with the original closed shaft setup. What is involved in changing to open drive shaft setup. I have a transmission that is for open shaft, that I plan to install.
 
Randy1944 said:
I have a 1939 with the original closed shaft setup. What is involved in changing to open drive shaft setup. I have a transmission that is for open shaft, that I plan to install.
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It is fairly involved and there are several ways to do it.

You are lucky in that, on this forum over the years there have been literally hundreds of posts on that exact subject.
Try the search function. It will take you most of the night to read it all.
 
I have a three speed, top shift case 78-7006, that needs to be rebuilt. I hope to rebuild it with synchronized gears.
 
Randy1944 said:
I have a three speed, top shift case 78-7006, that needs to be rebuilt. I hope to rebuild it with synchronized gears.
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Only second and third are synchronized. Ford started synchronizing them in 32. You’re not really gaining anything by going to an open drive and using that transmission.
 
If I decide to keep this transmission as a backup for my 1939 pickup, what can I change to adapt it for use on the closed shaft setup on my truck? Appreciate the advice and suggestions.
 
Randy1944 said:
If I decide to keep this transmission as a backup for my 1939 pickup, what can I change to adapt it for use on the closed shaft setup on my truck? Appreciate the advice and suggestions.
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Yes, so can. Like Kurt mentioned, changing the main shaft and bearing retainer, etc. But, I need to ask why you want to?

If I were you, stick with the closed drive trans set up currently in your truck. You are not gaining anything with the Ford open drive and you will need to do some fab work to the center cross member and figure out how to stabilize the rear, split the wishbones, etc. The wishbones alone are not strong enough to hold the rear in place long term.
 
Much simpler to change a few parts in the transmission with wrenches than to rework the X member and rear suspension with saws and welders.
 
After considering all advice, I think I will be better off to stay with the original closed shaft set up. My setup in my 1939 Ford pickup does pretty good(it jumps out of gear some). I was able to obtain a top load transmission that looks to be a 1948. Previous owner took it apart because some gears are chipped and never put it back together. I would now like to rebuild it and have it as a backup for my truck. Besides damaged gears, what parts do I need to change out. Where can I get the used “Main Shaft Bearing Retainer” #78-7085 B? Thanks for the help.
 
Randy1944 said:
After considering all advice, I think I will be better off to stay with the original closed shaft set up. My setup in my 1939 Ford pickup does pretty good(it jumps out of gear some). I was able to obtain a top load transmission that looks to be a 1948. Previous owner took it apart because some gears are chipped and never put it back together. I would now like to rebuild it and have it as a backup for my truck. Besides damaged gears, what parts do I need to change out. Where can I get the used “Main Shaft Bearing Retainer” #78-7085 B? Thanks for the help.
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Randy:

First things first. Order the transmission rebuilding book by member Mac VP.

Jumping out of gear is an indication that your transmission needs to be rebuilt, so sooner or later you'll be faced with this task. If you have mechanical ability, Mac's book walks you through the process step by step. Best part, he has all the parts you need for the job.

Mac's book will also help you identify what you have with the spare trans. Don't trust anyone's word for it. Make sure by ID'ing the parts that you have. These parts look similar to the eye, but can be very different if the tooth count isn't confirmed, etc.
 
Ditto on Mac's there are a lot of things that have to be to spec to make it all work.
He will take you thru all of them.
 
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