39 gears in Model A drivetrain

C

Cartravel

Senior Member
I have some 39 gears I want to install in a Model B transmission case. I've rebuilt v8 transmissions before, but are there any issues installing them in a Model B case? It is to be mated to a Model A driveshaft. Can I use a v8 u-joint, etc. and rear mount? Sorry, if this has been addressed before. I've messed with v8s and Ts, but this is my first project involving Model A components.
 
ModelA29 said:
I'm not sure if they will fit the 39 was a syncro trans the A/B was not. Van Pelt has a lot of info and parts - http://www.vanpeltsales.com/FH_web/flathead_transID_3speed.htm


Cling's makes a kit to put the 32-53 trans in the A - https://www.clingsaftermarket.com/addtocart.asp?prod=3000
Click to expand...

The Model B (and the V8) was the first of the Ford synchro transmissions. They got better as time went on, the '39 being the best. The gears go in but if I remember correctly you had to assemble it in a certain sequence and maybe do a little grinding on the case, call Van Pelt. Remember you are also going to need the '39 shifter tower. You are also going to need to figure how to mount the clutch/brakes (Model A had them on the transmission, Model B on the frame) and the wishbone (Model A had it on the transmission and Model B had it on the frame). You are also going to need the cover for the U-joint for the Model B as the Model A was different. The rear mount went to the K member in the ,32 so you will have to get creative. According to the Green Bible the B7090 U-joint fits 1928-1948. Good luck, I decided to use the Model A transmission when I put a Model B engine into my Model A. The photo shows my Model B.



Charlie Stephens
 

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It is easier to buy a Cling's adapter kit, because the B bell housing side-bolts on the B are at a different height than the A housing. Then you have to figure out clutch linkage and wishbone mounts. The rear bearing/trans mount will all be OK, as is the drive shaft length.
 
1939 was the change year for the new style synchronizer. It requires the 91A 2nd/high shift fork. It will work with the vertical type towers of either single detent or double detent persuasion. The 32 through 35 have the tower that angles back toward the rear. The 91A fork is not a bolt in. Some folks fabricate a fork to fit but I'm not sure how it was done.

Mitchell makes synchro gears to work in their iteration of the model A transmission case.
 
I probably should explain more about this project. I've got a Model T engine with an SR Fronty head and SOC. The head was originally a pushrod setup, but in 1929 they developed the conversion to an overhead cam. They also sold a pan to convert to use of a Model A transmission. Mine has a homemade conversion, not the Fronty conversion. It has the front portion of a Model T pan and the back of a Model A or B (not sure which). It looks like a Model B case will bolt up to it. I'm planning to use Model A parts behind the transmission. I have a very rough Model T Mercury body which I will restore and use. Mercury bodies were lowered by replacing the rear portion of the Model T frame with a kickup or z'd frame section. I can modify the wheel base with the position of the kickup. I'm mocking everything up to see what kind of wheelbase I get. I may need to shorten the drive shaft.


Thanks for the tips. I've used van Pelts excellent book, so I'm aware of the compatibility issues between 39 and earlier v8. I might be able to use parts of the Cling conversion, but I'm sure I'll have to do some fabrication too. I was looking at the u-joint cover and rear mount yesterday. It looks like a v8 rear mount and u-joint cover fit the curvature on the Model A torque tube. Am I missing something?
 

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Hi Larry- one thing to check with the crank flange- i assume you have an A crank in that motor. The rear of the crank flange will be about 3/8" too far forward to align the flywheel surface the same distance from the back of a Model A/B block to the crank flange. I've done several dry clutch conversions and this is something to be aware of. Dan
 
I believe it has a counterweighted B crank. I understand these can be hard to grind due to the counterweights. I may decide to switch to a Skat crank if it simplifies things. Dan, I need to call you about some other issues.
 
1. The Cling's adapter is for using a V8 transmission with a Model A /B engine. This will not work with Model B transmission.

2. You need a Model B transmission ADAPTER Kit for fitting the B transmission.

Berts Model A Center manufactures the Model B transmission ADAPTER Kit. I understand that recently the Covid thing has affected parts for this kit.

Correction: previous link did not work here is phone number instead.

1-800-321-1931

Additional info here:

NOTE this info is about the Model B transmission case being installed not the V8 with the Aluminum bell housing adapter.

https://modelastore.com/transmission-clutch-shifter-parts/transmission-parts?product_id=3655
 
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Cartravel said:
I believe it has a counterweighted B crank. I understand these can be hard to grind due to the counterweights. I may decide to switch to a Skat crank if it simplifies things. Dan, I need to call you about some other issues.
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There were two types of counterweights. One type pressed on and was difficult to grind. The other was not a problem.

Charlie Stephens
 
You'll need a 48 or 78, V8 Ford transmission case. Plus you'll want the '39 double detent transmission cover. It's not quite as simple as it seems but can be done. Also, you say "I've got some '39 gears", what cluster and main shaft do you have? Also, what gear ratio do you have in the rear end? You cannot simply start mixing gears. I suggest you get Mac Van Pelts V8 transmission rebuild book and study these transmissions first. Knowledge is power as they say.
 
The most useful part of the kits may be the pedal assembly. The rearend should have standard gears. Is that 3.78 for an A (same as v8)? The transmission will also be standard 16/28 gears which gives the ratios 2.8, 1.6 and 1. Seth, as I mentioned I've had van Pelt's book for years and have used it to rebuild v8 transmissions. I'm well aware of compatibility issues within the v8 years.
 
The 1939 gears will fit in the B trans, I have done it. It takes a little finagling to get it done. There is not as much room in the bottom of the B trans case as in the V-8 case.
Its been awhile but I think the cluster had to be laid on the bottom of the case as
everything else was put in and brought up last and had the shaft pushed thru it.
 
I have done both the B and Cling's adapter setups. Go with the Cling's adapter setup, much better. The B requires special motor mounts.
 
If you are using a B transmission on a B engine in a Model A, we make the kit for the wishbone, the pedals, the parking brake and the clutch release shaft , to do this conversion. It is part # A-7002 for $235, available on Modelastore.com.
In stock. Ships same day
 
SteveB31 said:
If you are using a B transmission on a B engine in a Model A, we make the kit for the wishbone, the pedals, the parking brake and the clutch release shaft , to do this conversion. It is part # A-7002 for $235, available on Modelastore.com.
In stock. Ships same day
Click to expand...

Steve, is there a RHD version?
I have a 1935 gearbox that feels OK but I have no idea what it is like inside. I'm thinking that if it's not too difficult, I might graft '39 internals into it go go for a ride. What is the availability of '39 internals like?
 
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