1939 Transmission Rebuild Question

[Nasukau]

Hi All,
I just finished up my 1939 transmission and while it is on the bench I am able to shift into reverse and 1st easily. I cannot get it to shift into 2nd at all and I can get it into 3rd but it is tough to do. This case did not come with a shift tower. I had a tower someone had given me but it is a single detent but has the large fork. My question is if the issue of not shifting into 2nd might be the tower due to it being a single detent? I followed Vanpelts book when putting it back together. I do not think I missed anything.

Thanks,
Denny

[cas3]

the single detent should shift the same. does it move easy when not on the tranny? did you take it apart and clean it out? shift covers can be grabbed in a vise to feel the movement, careful not to squeeze too hard, or vice grip down on the edge of a work bench, again careful on the gasket surface, but at any rate it should go thru the motions without a fight. if not, rebuild it. if it works on the bench, and not on the trans, we need more info on what has been done there. i assume you are turning the input shaft while trying to shift to 2nd and 3rd? things must line up to select a new gear

[hardtimes]

Originally Posted by Nasukau

Hi All,
I just finished up my 1939 transmission and while it is on the bench I am able to shift into reverse and 1st easily. I cannot get it to shift into 2nd at all and I can get it into 3rd but it is tough to do. This case did not come with a shift tower. I had a tower someone had given me but it is a single detent but has the large fork. My question is if the issue of not shifting into 2nd might be the tower due to it being a single detent? I followed Vanpelts book when putting it back together. I do not think I missed anything.

Thanks,
Denny

Hey Denny,
As I remember back a dozen years, I seem to have had that same problem.
Check out the BALL on the end of the shifter. It has to be a certain size and not worn. Maybe vanpelts book will explain further detail. As I remember, I enlarged the worn ball and fitted it back to stock size.
I would look in my vanpelt book for notes I used to make, but I loaned the book to someone here and haven't got it back....yet.

[pooch]

Prob your single detent top has a ground out shifter fork.

It does not throw 2nd gear in.

You ned the correct tower .

[flatheadmurre]

Sometimes if the syncronizers are put on dry they are a bear to move by hand and makes shifting into 2nd and 3rd hard on the bench.

[Juergen]

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There are lots of 3 inch forks in double detent towers advertised on e-bay which won't work with the later gear set. Always look (and ask) for the 91A-7230 casting on the fork. If it is not there, it is likely the earlier style. Some early style forks have the 68-7230 casting number but most have no number. The 91A fork fits in the earlier single detent tower.

[Karl Wolf]

It's my belief that the position of the 91A fork is different between the early and late lids.
When you put the lid on, check the position of the 2nd/3rd fork in relation to the slider.
My bet is that the slider is off center to engage.
Give Mr. VanPelt a call.

Karl

[rotorwrench]

There are two different design synchronizers. One is the initial type used in 1939 and in later trucks of the 8BA family that has the spring rings and plates. The other is the one with the balls and springs. The ball & spring type can sometimes get things out of place or they don't go together correctly causing 2nd high shift problems. There are some late manufacture brass blocker rings that aren't made correctly and can cause shift problems. There is a way to check them out published in Mac VP's book. There are other things but this is a start.

The trans has to be rotated in order to initiate movement of shifting mechanisms & gears but if there is an internal problem, rotating the input won't help much.

The 91A synchro shifting fork should fit and work with any of the straight up early Ford center shift towers and it's positioning of the synchro is key to proper function of the improved design from 1939 on to 1950/51. It won't fit the early slant back type towers thru 1935.

[Nasukau]

I took the tower off and the large fork has not been grounded. The only way i was able to move the large fork was by using a hammer and a punch to knock the fork up and down. It would not shift with the stick. Only the small fork would move. I’m assuming something is wrong in the detent. Does that sound correct? Or is it something else?

Denny

[Mac VP]

Normally you can move either shifter fork into a gear position with a whack from your hand, or a bump from a soft hammer.....assuming that the other fork is in its neutral position. In my example, the shifter housing is off the transmission. You may have to remove the detent parts to inspect for a problem there. Since you say that you have the 36-38 single detent tower, that means taking it all apart to check it out. These towers have a single spring placed between the two shift rails. The spring will have hollow caps.....one at each end. The caps can get worn through on their rounded ends. We have replacements for this.

You should check the action on the synchro outer sleeve while you have the shifter housing off. Since your initial complaint was that the transmission would not shift into second gear, try manually shifting the synchro sleeve back towards second gear. With a little persuasion and slightly rotating the gears, the sleeve should easily move all the way back against second gear (covering both the brass synchro teeth and the small steel synchro teeth on second gear). If you find that it absolutely will not move there.....or is extremely difficult to make it go there, you probably have a problem with the synchro assembly. That could be an assembly problem, or defective bronze synchro rings. There were some rings made a few years ago that did not have the blocker slots machined correctly.

[Charlie ny]

If all else fails the problem might be in the manufacture of the brass syncro rings.
From the tooth side of the ring to the bottom of the THREE key slots the dimension
should be .302/.303. Many rings are heavy......312 or more. That extra material
reduces or eliminates needed running clearance. An easy way to check this out is to
loosen up the front bearing retainer and yank the main shaft out a bit. If your shift situation get better it's a good bet that your syncro rings are at fault.
Charlie ny
Charlie ny

[revkev6]

Question, since I'm stuck on the couch with a bum foot and my Mac van pelt book is in my garage does anyone know how much oil I should put in my 39 trans? I just refreshed it with new syncros bearings and thrust washers

[rotorwrench]

The old Ford literature gave quantity in pints but most folks put the level very near the bottom edge of the threaded filler port. The OEM quantity might be less than that but the old units have a tendency to shed any excess one way or another. I don't have my Ford shop manual with me now so I can't give you the recommended quantity. Maybe some one else can do that before I get out to my shop.

[Mac VP]

2-1/2 pints......that should bring the level on an empty transmission right up to the bottom edge of the filler plug opening.

[Nasukau]

I have a friend with a working 1939 double detent tower so I can swap it on their. If it wont’t shift into second or third then I might have an issue with the syncro’s too. Will post my results after the switch.

Denny

[Nasukau]

Got my friends 39 tower and tried it out. Had the same issue and couldn’t shift into 2nd but I could shift into all other gears. After comparing my gears to a picture on vanpelts website I now noticed my rookie mistake and put the syncro on backwards! So I will take apart and put it back on the correct way and then try the towers again. Thank you to everyone for the advice. Will post my conclusion after I make the correction to the syncro.

Denny