39 transmission problems

J

Jay in Mass

Senior Member
I'm posting this for a friend who has not yet signed up with this forum. His 39 transmission pops out of 2nd and 3rd gear. This happens both when he is slowing down and accelerating. Most of the time it happens while accelerating. Looking for suggestions. Thanks in advance for any and all help.
 
, you didnt say if the trans is making noise ,so my guess is worn teeth on the 2nd and 3rd gear on the cluster gear. worn gears on the main shaft, bad syncro, if noisey trans, front main shaft bearing, or the pocket bearing in the main shaft
 
Happens on aceleration and deceleration? You friend knows what to do. He just hasn't come to terms with accepting the obvious fact yet.

There is no easy fix for this situation, as far as I know.
 
Sometimes things just wear out. Worn gear teeth, worn thrust washers, bad bearings, etc. His problem is a common one and can be attributed to any of these and some other potential problems. Solution is to tear the trans down and go thru it piece by piece. He can try it himself or send it out to a shop for this work. We do them here in Ohio, but there are others who may be closer.
 
If it slips out of 2 and 3 there is a fixed distance from 2 to 3 my guess something to do with shift top cover lever or something is broken or pin sliping.
 
Mac VP has the answer, no doubt about it... But I would check the detent spring first, as this can be done with relative ease. I have a trans that would fall out of second, put in a much stronger spring and am still using this same top on another trans... no shifting probs... Karl
 
Karl is correct in checking the detent springs. This is sometimes easier said than done however. If the detent plugs are rusted/stuck in place, you have to worry about damaging them to get them out. It's very easy to damage the screwdriver slot, and then have no way to unscrew the plug.

Since we do these shifter housings all the time in the shop, we had a special tool made that fits our hydraulic press. It is essentially a wide blade screwdriver (ground to fit the plug slot closely) that it fitted into a holder. The holder is attached to the ram of our press, and it incorporates a ball bearing swivel just below a hex shaped body. With this device, we can block up the shifter housing on its side, run the tool down onto the plug slot with a bit of extra pressure. Then we use a wrench to turn the hex just enough to loosen the detent plug. Once loosened, the tool is raised (we flip the shifter housing over and do the opposite side plug) and then the plug can be unscrewed the rest of the way with a regular screwdriver.

The detent plugs are not reproduced right now so, saving the old detent plug is very important. I've never had a plug that failed to come out properly with this device.
 
Re: Thank You

Thanks guys for all of the great suggestions. I just called my friend on the phone. He stated to me that the gears looked good when he installed it during the summer and that it is nice and quiet. I told him that the first thing he should do is take off the top cover and check it out thoroughly and be careful that he does not mess up the set screws. I know for a fact that sometimes they can be fun to remove. ( Can't understand why he is having trouble getting signed up with the forum.) So for now I'm hoping that he might find the problem in the top cover before he goes through the fun of removing the rear end.
I'll keep you up do date on what he finds and what he is doing.
This is a great furum. We have a lot of smart people who have been there and done these thing before and the nice thing is that they are willing to share their experiances to help other flathead persons.
 
Re: Thank You

Jay in Mass said:
Thanks guys for all of the great suggestions. I just called my friend on the phone. He stated to me that the gears looked good when he installed it during the summer and that it is nice and quiet. I told him that the first thing he should do is take off the top cover and check it out thoroughly and be careful that he does not mess up the set screws. I know for a fact that sometimes they can be fun to remove. ( Can't understand why he is having trouble getting signed up with the forum.) So for now I'm hoping that he might find the problem in the top cover before he goes through the fun of removing the rear end.
I'll keep you up do date on what he finds and what he is doing.
This is a great furum. We have a lot of smart people who have been there and done these thing before and the nice thing is that they are willing to share their experiances to help other flathead persons.
Click to expand...

Tell him to keep his right hand on the shift lever when he is accelerating or decelerating and the problem is cured. Just kidding
 
There is generally too much front to back slop and it causes it to pop out of gear when you are on and off the gas. Take the lid off, hold second gear and move it front to back. There should be less than .010 play in it. Any more than than will cause it to pop out of gear. I've been through this before, everything needs to be within spec. hope this helps.
 
The 2 nd gear problem is very common.The 3rd is a new one here.First off what was the orginal problem basket case or what.
If it worked ok before in 3 rd was the main shaft or bearing changed.Check to see if sleeve is not on backwards,and going far enought forward to grab main shaft.Shift into 3rd all the way then remove cover and check sleeve position.Maybe be assemble problem or fork pin.
 
Just a reminder o be sure the friend does not drop he pin in the cover if he unscrews the shift handle!! OPPS
 
You may want to give this fellow a call. He is on ebay selling these products and his phone no.is included. Marv
99% of all of top shifter mechanisms that I rebuild, the springs are broken and have lost their tension. Also, the 2 balls are usually flat spotted. This kit doesn't look like much, but, these are all specially which are made here in Cleveland, Ohio. This kit is like putting VIAGRAin your top shifter! The following items are included: 1) 2 special heavy duty springs-3 times stronger than original 2) 2 undersized balls which fit better in the shift rails 3) 2 new roll pins which hold the folks to the shift rails 4) 3 new welsh plugs 5) a new 3-piece bullet shaped unit which takes the place of the solid steel bullet in your shifter 6) an instruction sheet. You won't believe the extra snap and positive shifting you will receive after this installation. This kit fits only 39 and later tops (39 car and 39-52 light duty pick ups). I have sold hundreds of these kits and everyone loves them. FREE SHIPPING IN U.S.!! I have vastly improved the 1939 (and later) Ford top shifter repair kit to the max!! There is a bullet shaped unit which is a solid piece between the 2 shift rails. I have made a new unit which is split and has a heavy duty spring between them. The unit keeps a more positive pressure on the shift rails. Eliminating the jumping out of gear problem. If you have already bought my old kit previously, please give me a phone call about updating your kit. Thanks, Hot Rod John at 330-468-3027.
 
Item number:190419592484Item number:190419592484Item number:190419592484Item number:190419592484Item number:190419592484Item number:190419592484190419592484 190403757280 Here is the items numbers of the trans parts on ebay to match the post above. I hope this helps and wander if anyone here has used these updates for the old Ford transmission yet and how they worked. Marv
 
I posted, "Just a detail ... what engine is this installed behind?"

Never got an answer to that.

Everyone has taken for granted that it is a '39 transmission bolted to a ... '39 flathead.

What if it isn't? What if, for example, it's behind a SBC?

Non-standard match-ups introduce a whole bunch of new possibilities. While we probably are talking flathead to flathead, for those of us that have been involved with odd engine/transmission combinations, it'd be a great help to know what engine we are discussing in this case.

Still would appreciate an answer.
 
Beware of the "Viagra" fix kit. The complaints I hear have to do with difficulty in moving the shifter lever out of any gear. It slaps a bandaid on what is basically a problem inside the trans that should be repaired properly. Also, the kit substitutes the center "bullet" in the 81A-7222 shift tower with a spring and two detent cups. With these in place, you lose the positive interlock of the trans, meaning that it is now possible to shift both rails into gear at the same time. This will lock up the trans gears RIGHT NOW.

If the regular detent springs are broken, there will be little or no pressure on the detent balls (which help hold the shifter lever in place). Also, the balls can be worn or pitted. I would start here with these two items. After that, you should consider what is happening down in the gearbox. Assuming all the clearances in the gearbox are within spec, I would be looking for wear on the internal splines of the synchro outer sleeve (7106) and/or the mating synchro teeth of either the Main Drive Gear (7017) or second gear (7102). If any of these are worn, there will be little contact surface for the parts to "grip".

If the cluster gear, or second gear on the mainshaft are loose (too much front-to-rear) movement, you can also have problems with the trans popping out of gear.

If the shifter lever....or the 2nd/high shifter fork.....are worn where they fit together, the action of the shift into 2nd or high may not be enough to place the synchro outer sleeve completely over the mating synchro teeth of these gears. The contact point on the lever is the round "stub" that sticks out of the side of the lower end of the lever. It should be 0.500" round (1/2"). The slot in the 2nd/high shift fork where that stub goes should have a width of perhaps 0.505" (1/2" +). If either is worn, when you move your shifter lever into those gears, you'll perhaps feel the detent ball & spring do their thing, but the synchro sleeve may not be fully advanced into either gear, resulting in a "pop-out" condition.

Last but not least, the synchro cones (the shiny machined tapered part on the Main Drive Gear and on Second Gear) may be worn. You can't really see it but it can happen. Take a new bronze synchro ring and place it on the taper. There are two tests I do. With a drop of oil on the taper, try pressing them together with your hands while rotating them counter to one another. The rotating action should be a bit difficult. Also, when pressed together, look for a gap of about the thickness of a dime between the two sets of synchro teeth (the bronze teeth and the steel teeth). If the synchro teeth abut each other, the taper is worn (again, testing with a new bronze ring).
 
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