39 standard transmission woes

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Dennyd928

New member
Hello guys, I am new to the site, and new to this era Ford.
I purchased a 39 Standard Tudor in need of a transmission.
I purchased a 51 F1 transmission with yoke. My local driveshaft and axel shop installed it, purchased a kit to change rear end to open driveshaft. There isn't enough clearance through the X member for a 3" driveshaft.
I can't believe I'm the first guy to install a newer Ford transmission in a 39.
Looking back, I should have rebuilt the original transmission.
Any help with my problem will be greatly appreciated.
 
Go back to the original 39 transmission and torque tube. That setup was great.


Do you still have the rear radius arms? You understand Ford used the torque tube and radius arms with a transverse leaf spring for a reason, correct?
 
The case from a 51 F1 will accept the closed drive rear housing from any 48 or earlier passenger car case whether side shift or top shift. The longer mainshaft will be needed along with the rear housing. Get yourself a copy of Mac VanPelt's early Ford transmission book. It lets you know what parts will work together. Parts Sources carry "The Ins and Outs of the Early Ford Transmission ", or you can get it on the VaPelt Sales website.
 
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rotorwrench, you mentioned a longer main shaft and rear housing. I have the original rear housing, will I need to take the long main shaft out of the 39 trans? I hoped to avoid disassemblng these transmissions internally.
So the best idea for me is to cut my losses with the open driveshaft parts and go back to a closed driveshaft? All I asked for was guidance on my fiasco.
 
Welcome Denny, The 39 box is simple and not a bad unit for normal use. Assembly is also very easy. Start by telling us what was wrong with the trans in first place so we have a starting point. This will be fun, Tim
 
Dennyd928 said:
rotorwrench, you mentioned a longer main shaft and rear housing. I have the original rear housing, will I need to take the long main shaft out of the 39 trans? I hoped to avoid disassemblng these transmissions internally.
So the best idea for me is to cut my losses with the open driveshaft parts and go back to a closed driveshaft? All I asked for was guidance on my fiasco.
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My first transmission overhaul was on my family hand me down early 1951 Mercury. The transmission is based on the early Ford units except the R10 overdrive was added on these. The unit has the same synchonizer set up and the same type input gear, 1st/rev gear and cluster counter shaft gear. The mainshaft for the overdrive and the reverse lock out made the big difference. I have a 39 transmission as well for an AV8 project. The only transmissions that are more simple are the 1932 through 1938 units since they have different synchros and some gears with the exception of the 1936 and up cluster gears and a few other pieces as long as they are for helical gear applications. The only problem I had in disassembly are the retaining rings for the bearings. Ford used rings that are difficult to remove but not impossible. I replaced all of them with Mac VanPelts ring kit which are correct in width and inner & outer diameters plus they are easy to install & remove with old style snap ring pliers. Everything else is fairly easy with basic tools.

If you already have a 39 transmission then you have all the parts needed as long as the parts are serviceable among the parts you have. Critical items are the thrust washers for the counter shaft, the blocker rings for the synchro, and the condition of the case that you want to use. Both cases are the 78 series and are interchangeable. The top shift towers are also interchangeable. Pickup gearing can sometimes be different and this is where Mac VP's book is a must. It lists what was intended to work with what as well as having excellent instructions for overhaul or repair. If bearings are still good, I tend to reuse them. Some new bearings are crap. The input & counter shaft small internal rollers are a good example. No company makes them like Hyatt did.
 
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If the OP had a shop install the open drive trans, I'd assume there were frame & rear end mods done to accomplish this. If that's the case, may be simpler, as Proartguy, mentioned to have a smaller diameter drive shaft made than to undo all the mods that were done for the open drive.
 
The big problem with chucking the torque tube is the loss of rear axle stability. The rear axle needs radius rods and a center rod to keep the rear axle in check unless the rear spring is changed to dual springs but that is also a lot of work. Most street rodders change the X member to open it up for a drive shaft but that also changes the rear engine/trans support. More work to do to shore up the frame member and add mounts for either radius rods or dual springs.

I guess it depends on how far the job got before the drive shaft problem was noted. Sometimes there is a point of no return. What would have been a relatively simple transmission repair or overhaul turned into major surgery.
 
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Just shows to go ya, do your own homework before relying on a local shop to know what they need to know before taking on a job.
 
I should have mentioned the transmission stuck in second gear. I got the car home and took the top off the transmission. forks look good. Issue seemed to be with synchronizers. After reaching in and messing with them, I got it out of second. I changed oil , Put top on, and went through gears. seemed good. took car out for a run and it stuck in 2nd right away. It did pop out of gear on deceleration This transmission supposedly was rebuilt in 2021 by a shop in Lancaster Pa. I live about 30 miles away near Reading Pa.
A 3" diameter driveshaft is minimal. I decided I don't want to lift off the body and cut out the X member.
This is a survivor car, nice driver, not a show car or street rod. Rebuilding the original transmission is probably my best recourse.
If anyone lives in Eastern Pa and give me guidance on rebuilding the stock trans, please contact me. Or if anyone can recommend a shop experienced with these old units.
Thanks!
 
Dennyd928 said:
I should have mentioned the transmission stuck in second gear. I got the car home and took the top off the transmission. forks look good. Issue seemed to be with synchronizers. After reaching in and messing with them, I got it out of second. I changed oil , Put top on, and went through gears. seemed good. took car out for a run and it stuck in 2nd right away. It did pop out of gear on deceleration This transmission supposedly was rebuilt in 2021 by a shop in Lancaster Pa. I live about 30 miles away near Reading Pa.
A 3" diameter driveshaft is minimal. I decided I don't want to lift off the body and cut out the X member.
This is a survivor car, nice driver, not a show car or street rod. Rebuilding the original transmission is probably my best recourse.
If anyone lives in Eastern Pa and give me guidance on rebuilding the stock trans, please contact me. Or if anyone can recommend a shop experienced with these old units.
Thanks!
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If you are willing to do it yourself, order the transmission book from Mac Van Pelt. It will walk you through all aspects of rebuilding the transmission.

Regarding second gear, there is definitely something going on with synchronizer. Sometimes the blockers & springs & balls get messed up; especially if it got into an "over shift" (meaning pushed too far) into second. Either way, something isn't right with the trans you have in there.


One of the root causes of the dreaded popping out of second is having too much end play in the gear cluster assembly within the case. Generally, this pop out happens during declaration. The gear thrust during acceleration wants to "push" the cluster upward. When you let off the gas, the cluster "relaxes" and "moves" too far forward or aft which impacts the synchro enough to pop it out of gear.

Good news is Van Pelt Sales sells different thrust washers in various thicknesses to allow you to get the exact end play you need. It does take some time and often multiple removals of the cluster to get it right during the rebuild, but the end results are well worth it.
 
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Seeing that this transmission is supposed to be a recent rebuild and the fact that everything inside looks good to you, it's probably a minor problem like Tim says. I second the suggestion to get Van Pelt's book and go through the transmission yourself. You'll probably end up with an excellent transmission with a minor amount of time and expense. I was a rank amatuer when I rebuilt a '39 box with later gears about 30 years ago, and it turned out great. Just be careful, measure everything twice, and you'll end up with a world beater.

My main concern is the possible damage done by what sounds like an outfit lacking the requisite knowledge needed for a task such as this.
 
It could be a synchronizer problem or a gear problem with too much play in the gears & shifting. The helical gears thrust a fair amount under load. Load them and they push to one side, unload them and they push the other way. This is where the thrust faces have to be in check with minimal play. The second gear is held by the synchronizer so if it or the cluster is moving around then function will be problematic.

The shift arm ball on the bottom can get worn, or the fork notches, or. both, then it may not shift all the way into gear. All stuff that needs inspection.
 
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rotorwrench said:
It could be a synchronizer problem or a gear problem with too much play in the gears & shifting. The helical gears thrust a fair amount under load. Load them and they push to one side, unload them and they push the other way. This is where the thrust faces have to be in check with minimal play. The second gear is held by the synchronizer so if it or the cluster is moving around then function will be problematic.
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What has me thinking the synchro springs & balls or sliders are out of whack was that it jammed into 2nd gear and he had to manually slide it back into place.

Originally poster, was it easy to do this by hand or did it take some force to get it back into the center position?
 
My 39 unit came with the synchro that has three plates that use spring rings instead of coil springs and ball bearings. The plates have bumps to act as detents. After so many years, it could have either synchronizer. The coil springs and balls can get worn or broken and that is problematic for sure.
 
rotorwrench said:
My 39 unit came with the synchro that has three plates that use spring rings instead of coil springs and ball bearings. The plates have bumps to act as detents. After so many years, it could have either synchronizer. The coil springs and balls can get worn or broken and that is problematic for sure.
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The sliding-blocker type like yours is the better of the two designs in my opinion.
 
It's hard to beat a '39 Ford Toploader transmission they are GREAT.
Hard to find today because all the guys who raced Flatheads wanted that '39:)
 
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