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Technical 1939 transmission fault

Discussion in 'Traditional Hot Rods' started by Jukenut13, Jan 1, 2019.

  1. Jukenut13
    Joined: Feb 10, 2013
    Posts: 29

    Jukenut13
    Member

    Hi, I agree with your comments on the later type. I will double check tomorrow but the syncro sleeve I replaced was marked/polished on the front edge and this is what I think produces the noise - rubbing against the cluster. This is a 1939 trans that could have either early or late style syncro .
     
  2. clem
    Joined: Dec 20, 2006
    Posts: 3,814

    clem
    Member

    Excuse my questions, as I’m still learning about these transmissions ;

    I’m curious as to what you mean by ‘small syncro’ ?


    From the way you describe it , and pictures, it appears that you have all ‘36 parts, or am I wrong ?
     
  3. Mac VP
    Joined: May 13, 2014
    Posts: 411

    Mac VP
    Member

    I would assume that you’ve had this transmission apart since you mentioned replacing the synchro sleeve. The question I have is not answered by the pictures......was the synchro hub reinstalled correctly? They have a sort of snout on one side, which should face forward. And of course, there should be no snap ring fitted in front of the synchro assembly.

    The shifter levers from 1936-39 have a straight vertical profile when viewed from the side. If the lever was bent slightly (below the pivot ball) it would position the synchro sleeve incorrectly.

    Just trying to help look at possibilities..... I do agree that the balls appear to be overexposed. In fact, with the small springs under them, I’m surprised they haven’t popped out already
     
    Jukenut13 likes this.
  4. 48-760
    Joined: Dec 15, 2009
    Posts: 142

    48-760
    Member
    from OH

    I disassembled the top from a 36 in both 2nd and 3rd gear, trans was on the ground so not level. As mentioned previously the center hub of the syncro is supposed to move with ease back and forth. I had to move it fordward with a screwdriver to simulate how you should see it in mounted since gravity kept moving it toward 2nd gear. I believe Mac, above, has valid points to check 36 trans in 2nd gear.JPG 36 trans in 3rd gear 2.JPG 36 trans in 3rd gear.JPG
     
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  5. Jukenut13
    Joined: Feb 10, 2013
    Posts: 29

    Jukenut13
    Member

    Hi Clem, the ''small ''syncro is the early type that you see in mine. The later 1939 and on use separate baulk rings as in a modern car and the fork is wider and in a different position as in Pist-n-Broke photo .
    The later trans use all helical cut gears - I am 'new' to these boxes as well but used to more modern ones.
    Perhaps I should call mine a late '38 box...
     
    clem likes this.
  6. clem
    Joined: Dec 20, 2006
    Posts: 3,814

    clem
    Member

    ^^^^^^
    Thanks,
    I have just put a ‘39 box in my sedan, - same as the one in ‘pistnbroke’ post.
    But what I pulled out was supposed to be a ‘39, but from vanpelts web site I identified it as an earlier model, without the syncros.
    Clemens
     
  7. Is it possible to have the Sincro Hub in Jukenut13s gear box installed on the late 39 shaft and have a snap ring installed also? This would keep it stationary and maybe be the problem.
     
  8. 5280A2
    Joined: Sep 8, 2014
    Posts: 162

    5280A2

    He did say in his first post that he has the 68-7061B main shaft. That doesn't have the slot for the snap ring that appears with the later 81A-7061 main shaft for the late style synchro that does have a snap ring. As I mentioned in my last post I have a 38 transmission apart at the moment and took some photos that may help explain what is going on with the OP's transmission. The first two photos show the main drive and mainshaft in place without the synchro hub to illustrate the friction surfaces on the main drive gear and intermediate (second gear). The second photo shows the same thing with the hub installed and no sleeve. Based on my transmission, the hub must be able to move freely approximately 1/8-inch forward and backward to make contact with the friction surfaces on the main drive gear and intermediate gear. In the second photo the hub is engaged with the intermediate gear, note that part of the main drive (high) gear friction surface is visible with the hub in this position.

    IMG_3157.JPG
    IMG_3156.JPG

    The next photo shows the hub engaged with the main drive gear (high gear) and you can see how much the hub has moved forward by comparing the position relative to the intermediate gear, and you can see that part of the friction surface of that gear is now visible. As mentioned above, total travel of the hub on the main shaft is about 1/8 inch.

    IMG_3155.JPG

    The next two photos show the correct position of the hub and sleeve with the hub in contact with the main drive gear and the sleeve in the high gear position. Note that the synchro balls are still covered when the hub is in contact with the main drive (high) gear.

    IMG_3161.JPG

    IMG_3162.JPG

    The last two photos show the hub in its rearmost position, touching or nearly touching the intermediate gear friction surface with the sleeve engaged with the main drive (high) gear. Under these conditions the synchro balls would be nearly exposed as shown in the photos of the OP's transmission when the top is removed with the transmission in high gear.

    IMG_3163.JPG

    IMG_3164.JPG

    To me this is pretty clear evidence that the problem with the OP's transmission is that the synchro hub is not moving as it should when shifting into high gear. With the transmission in high gear the synchro hub and intermediate gear will be moving at different speeds, and that could be the source of the noise being heard. In my last post I suggested trying to pry the hub forward when the transmission is in high gear. I suppose it is possible that the hub is too bound up on the shaft to accomplish that. I have found that although the hub can be installed in six different positions (six splines on the shaft) some positions will be tight and some will be looser. I always try the hub in each of the six possible positions and mark it for the position where it moves most freely. The splines need to be checked carefully for any nicks or burrs that keep the hub from sliding back and forth on the shaft; it is only the tension provided by the six springs and balls between the hub and sleeve that allow the hub to slide along the shaft while shifting. Again, I would check to see if your hub is sliding on the main shaft as it should.
     
  9. brsturges
    Joined: Oct 22, 2008
    Posts: 913

    brsturges
    ALLIANCE MEMBER
    from Miami, FL

    ^^^^Post of the year!!!
     
  10. rusty valley
    Joined: Oct 25, 2014
    Posts: 3,605

    rusty valley
    Member

    very educational ! thanks
     
  11. Mac VP
    Joined: May 13, 2014
    Posts: 411

    Mac VP
    Member

    Great picture posts above and good comments about the positioning of the gears. I’m not in the shop to take similar pictures re the synchro hub, but I did want the OP to check his hub for the correct orientation. My picture here of the early hub shows the back side (the side that faces the 7103 second gear). The front side, not pictured here, has more of a snout which faces forward.
    http://www.vanpeltsales.com/FH_web/FH_images/Trans parts pics/B-7108hub.jpg
     
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  12. gh4ds
    Joined: Jun 13, 2008
    Posts: 1

    gh4ds
    Member

    This is a great thread. Kudos to those for all the technical input. I put the same setup in my '31 Tudor and had the same "singing" in third gear. I, like WD69, drove the car this way for several hundred miles. I am also running a Float-A-Motor engine mount. Originally, I had left the rear transmission mount off because I didn't think it was necessary and it required modification to fit properly. Along with the singing, the transmission would occasionally jump out of gear. I finally decided that the rear mount may be more necessary than originally thought. It may be coincidental, but the singing went away and the transmission stopped jumping out of gear after the rear mount was installed.
     
  13. rusty valley
    Joined: Oct 25, 2014
    Posts: 3,605

    rusty valley
    Member

    so mister 5280a2, your trans looks to be in good shape, and you certainly have some knowledge about it, do you feel its as good as the 39 style when working properly, or do you lust for a later gear set? thanks for your opinion
     
  14. Jukenut13
    Joined: Feb 10, 2013
    Posts: 29

    Jukenut13
    Member

    Hi 5280A2, thanks for your efforts , great photos and discription. I put my Mitchel o/d in neutral and held the clutch down while turning the gear train and sliding the syncro back and forth. A little bit oily etc. but every now and then the hub seemed to stick on the splines.
    I will remove the trans for inspection and compare with yours. I'm sure I put the hub on the correct way -but hey, after all this one does start to doubt ones self! Another thing - the origonal owner had no problems so I'm wondering also if there is an alignment problem with the drive gear - something else I can look at.
    So for now, thanks to all who posted and gave the info needed. Will post againwith my findings
     
  15. 5280A2
    Joined: Sep 8, 2014
    Posts: 162

    5280A2

    Great question! I have a lot more experience with the early parts so I'm not sure I can speak to the late style with much first hand authority. My driving experience with the late synchros is mostly a stock 1948 tudor with a side shift box and column shift; not too racy. My primary experience is with a 1936 gear set in a Model B gearbox behind a hopped up four banger in the roadster pickup in my avatar. Based on my experience with that I think the early style gear boxes are under-rated by most hot rodders. I have been using and abusing that gearbox since 2009 and it still shifts crisply and I can downshift into second gear at 35-40 miles per hour if I give the synchros a second or two to work before completing the shift. I have to say I have been very happy with the way it performs.

    I have built a few of the 39 style transmissions and ended up selling them without ever running one myself. The first one I sold was one of two I built for something to do over the winter here in lovely subarctic Minnesota. I did one 1936 transmission and one 1939 transmission and ended up keeping the early one for a future project. The other one sold quickly here on the HAMB and ultimately led to to other folks contacting me about building transmissions for their projects, which I did, and which used up all my late parts. So now I'm stuck with the "inferior" early transmissions and parts.

    I just put another B transmission with early gears behind a hopped up B motor in a 1930 coupe I bought last May. I expect that to be just as good as the one in my pickup. I've been lucky enough to find good early parts including a couple of NOS synchro hubs, so I think that has helped make the transmissions work as they are supposed to. The trick to both the early and late transmissions is to assemble them with good parts, new bearings, and proper clearances so they work the way they were designed. Good detents in the synchros and shifters are very important and relatively cheap and easy to replace. So long story short, I'm satisfied with the early style 'cause I don't know any better and I'm too cheap to find out otherwise........
     
  16. 48-760
    Joined: Dec 15, 2009
    Posts: 142

    48-760
    Member
    from OH

    If you take a look at Mac VP post above you can see the brass syncro ring inside the early style small syncro hub. There is an identical ring on the other side of the hub. The brass rings are swedged into the hub and should not rotate in the hub.
     
  17. Jukenut13
    Joined: Feb 10, 2013
    Posts: 29

    Jukenut13
    Member

    Well, today I removed the trans. On the bench, checked the syncro hub and it slide back and forth nice and easy in all positions about 1/8'' . Put it in in gear using the lever, looked correct with no problem. I have not stripped it as yet as thoughts kept going back to previous owner saying there was no faults but I noticed these from the start. There is some play in the main drive gear, you can wobble the shaft somewhat. When doing this plus rotating and sliding the syncro by hand ,the hub sticks a little and dose'nt go all the way on the friction surface untill you relax any side pressure on the main drive gear.
    So , is this an alignment problem in the main drive gear, the hub sticking and getting left behind allowing the balls to be exposed and slowly forcing the sleeve forward - there appears to be shiney marks on the sleeve front lip from the cluster (hard to see). The noise can take a while to appear at times.
    It was awhile ago when I fitted the Clings kit - which are great, but think I have fitted their adapter and have a runout problem causing the maindrive gear to be out of alignment?
    I fitted a pointer on the flywheel and found about 45thou runout between top and bottom of the machined face - see photo.
    The trans. is doweled to the adapter but I will have to see if the adapter will move slightly in relation to the flywheel housing?
    Your thoughts on this please ..... 101_0860.JPG sorry guys - ''typo'' , just amended to 45thou runout...
     
    Last edited: Jan 13, 2019
  18. Is the inside surface machined and true to the surface the Trans case bolts to? I would want to double check it there. I have used shim stock and placed between adapters and blocks before to square things up. Input shaft running untrue to Crank shaft will damage bearings for sure.
    The Wizzard
     
  19. 5280A2
    Joined: Sep 8, 2014
    Posts: 162

    5280A2

    I agree with the Wizzard about the ID of the adaptor. I don't see any reason that the manufacturer would bother machining that surface to be concentric with the crankshaft when all that is required to locate the adaptor and transmission is the alignment pins and bolt holes. I can imagine there could easily be as much variation as you are finding without any affect on transmission alignment. If you want to check for flywheel runout you should check the circumference of the flywheel from a single point on the adaptor or flywheel housing; a dial indicator would be best, but if you don't have one you can rig up something from one of the threaded holes an the adaptor to create a gap that can be measured as you rotate the crankshaft and flywheel.

    You mentioned play in the main drive gear, and that is an indication that the ball bearing on the main drive gear is worn and should be replaced. With a new bearing and the proper snap rings to retain the bearing on the shaft and in the gearbox there should be no side play or end play with the bearing retainer bolted in place.

    I would still recommend disassembling the main drive gear from the gearbox so that you can remove the synchro hub and sleeve from the transmission in order to test the detent springs and balls in the synchro assembly. With the proper tension on those components you should not be able to move the sleeve by hand; it should take either a fair bump from a dead blow hammer or the mechanical advantage of the shift lever to overcome the detents and allow movement of the sleeve on the hub. Even with the sleeve in position to be engaged with a gear, that is shifted forward or back from the neutral position, the springs and balls should require a fair effort to move the sleeve. It doesn't seem reasonable to me that the hub could "walk" on the main shaft if the detents are in good order.

    Can you slide the sleeve by hand with the cover removed from the transmission? If so, dig into the sleeve and detents.
     
  20. Jukenut13
    Joined: Feb 10, 2013
    Posts: 29

    Jukenut13
    Member

    Well , after a 10km test run, all seems well!
    I stripped the trans again just to recheck. I knew the syncro springs were strong but replaced spring and balls anyway then turned my attention to where I thought the fault was.
    As this was ok in the previous owners car I looked at the alignment/ fitment.
    The flywheel housing was reshimmed (although this was checked by the engine rebuilder some time ago). I then fitted the V8 adapter and as mentioned before, it was actually 65 thou low (from flywheel centre). This would give a misalignment on the main drive gear. I modified the housing to centre it up and bring the trans and crank into alingment. Refitted trans, now no noise. I believe the misalingment was enough to let the syncro hub partially stick and not travel the full distance and with the runout, allow the balls to try to force there way out therefore pushing the sleeve hard forward and contacting the cluster gear (this had witness marks to show this).
    This was the noise I heard. Possibly , the crankshaft was not centered correctly when recond.
    Many thanks to all who posted, hope this will be helpful to others. Now to move on to other items and put some miles on it.

    Ron, New Zealand.
     
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  21. 5280A2
    Joined: Sep 8, 2014
    Posts: 162

    5280A2

    Very glad to hear that you feel you have solved the problem! I hope you will be able to enjoy your car now. I hope you will notify Cling's about the alignment issue so that they can check their quality control in case the adapter was machined incorrectly. You are talking about nearly 1/16 inch of misalignment which to me is substantial and worth conveying to the manufacturer. I have dealt with them and believe they would want to remedy any problems with their products.
     
  22. Jukenut13
    Joined: Feb 10, 2013
    Posts: 29

    Jukenut13
    Member

    Thanks 5280A2, your photos were a great help. A very simple trans. but the changes in parts and numbers was confusing at the start. I think most of the runout was in the flywheel housing (lost my notes in the rush to get car ready for local carshow) which led me to believe the crank was off centre?. Contacted Dennis at clings and he said to check flywheel housing etc. Didn't have any spare housings to try so used Clings adapter to align - made it easier.
    Recommend the Clings adapter kit, easy conversion and neat and tidy. I let him know of my findings. The artical Dennis sent on alignment was very helpful, showed the misalignment in the flywheel housing. I could make the alignment correct using his adapter .
     
    Last edited: Jan 28, 2019
  23. continentaljohn
    Joined: Jul 24, 2002
    Posts: 5,323

    continentaljohn
    Member

    Bttt for some great tech/info
     

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