39 open drive transmission to closed drive

[Tinker]

Probably not asked much but what is needed to convert a 39 3sp transmission with an open drive setup back to a closed drive (torque tube) setup.

Would the output shaft need to be changed?

Also would the early 4sp transmission yoke and parts work also?

This is for a 39 truck currently with a 4sp truck transmission (not mine).

Thanks for any help.

[V8COOPMAN]

Here are the parts required to convert TO open drive. DD

[Tinker]

Need to go the other way...

[51504bat]

Seems to me there should be someone with a closed drive shaft trans wanting to convert to open that would be willing to work out some type of trade. JMO.

[V8COOPMAN]

I understand, but to answer one of your questions, you need to replace the mainshaft. DD

[Tinker]

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Thanks Coopman. I agree, looks like a bearing or bearing retainer is needed as well.

Have a couple transmissions to possibly use parts from. 4sp truck and a 40s sideshift (both closed drive)

[V8COOPMAN]

The side shift should have all the parts needed. DD

[Tinker]

That's promising.

Any tricks to removing the mainshaft? Are they pinned?

Any bearings or seals that are good to replace at this time?

Just trying to get info before taking it apart.

[V8COOPMAN]

You'd be smart to swap the entire guts of the '40 box into the top-shift box as a set. Replace bearings, etc. as a judgement call. Mac VP's book will help you thru all of this, as well as Mac's parts availability. DD

[Tinker]

Problem with that is the 39 transmission is a new rebuild. I believe I have that book I'll need to go dig for it.

[Tinker]

Nope don't have it. I'll have to do a spline count on the 40 as I see a listing for 40s transmissions having 6 and 11 spline output mains.

Thanks.