Automatic ****** in a Model A Ford

M

Mike/Nebraska

Senior Member
Looking for information about using a Ford C-4 or C-6 transmission to a Model A block. I know of one locally but the man who made it has since passed away.
 
Mike/Nebraska said:
Looking for information about using a Ford C-4 or C-6 transmission to a Model A block. I know of one locally but the man who made it has since passed away.
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Try Bendtsen’s Speed Gems Transmission Adapters. I think they use GM transmissions tho. Or check with Flat-O. I used their adaptor to install a C-4 behind my 318" Y-Block in my '55 Ranchwagon.
 
C-4 and C-6 are better suited for high horsepower V8 engines. I think they used a C-3 in the pinto that would rob less horsepower from the 4-banger. I have a C-6 in my '57 Ford, but it's with a big-block.
 
There is a Model A repair specialist here in the DFW area that put an early GM Power Glide in a Model A for a client. From what I've heard it worked out well, but I don't know the details firsthand.
 
Seem to remember years ago someone used a Dodge or Chrysler auto trans in an A with good success. The reason for that trans was its compact size.
 
stickshift said:
C-4 and C-6 are better suited for high horsepower V8 engines. I think they used a C-3 in the pinto that would rob less horsepower from the 4-banger. I have a C-6 in my '57 Ford, but it's with a big-block.
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Besides the Chevy Powerglide, the C-4 is known to have the least parasitic drag of most automajic transmissions. They were used behind 170/200" sixes in Falcons and early Mustangs but are stout enough to use with larger V-8 engines.

A A4LD would be a nice trans to concider, basically a C-3 with O/D. Bendtsen's has a kit https://transmissionadapters.com/pages/product-result?rq=yr_ford~lo_model-a-4-cylinder~mk_ford-a4ld

 
Any automatic trans. hooked to a 40 HP stock model A is going to be a significant loss of power. The engine can be souped up to increase HP but then there is always the weakest link in the frame or drivetrain that people experience. I don't know what change in mileage would occur. The advantage of having an automatic and ease of driving might outweigh the power loss for many people. Here's a list of power loss on popular transmissions published by a Car Craft article.

Powerglide - 18 hp
TH-350 - 36 hp
TH-400 - 44 hp
Ford C-6 - 55-60 hp
Ford C-4 - 28 hp
Ford FMX - 25 hp
Chrysler A904 - 25 hp
Chrysler 727 - 45 hp
 
The chart of drag is a nice set of data. Remember, the converter of an automatic has slippage up to cruising speeds. Which means that at 25MPH you are losing some efficency, as the converter has not yet achieved theoretical speed to get it to 1:1 yet. We also need to remember, that the converter should always be sized so that the "stall" is less than the RPM at highway speed. Otherwise the thing will never hit 1:1.
 
Their kit that can use a Chevy TH200c trans mentions the lockup torque convertor will get you an extra 300 rpm.


Instructions: https://cdn.shopify.com/s/files/1/0021/2415/2950/files/FO1001101.pdf?v=1592251539


Some of the other modifications that need to be addressed are: parking brake, manual brake linkage, torque tube rearend, crossmember, automatic shift linkage, cooler lines, etc. The transmission that I think works best with this setup is the 200/c transmission. It has the smallest overall case size and is very light. (about the same as the C4). It isn’t an overdrive transmission, but it has a lockup torque converter which can be good for about 300 rpm at highway speeds. It also has much better gear ratios than the 350th or the 400th, and is very reliable when built correctly. It would be wise to take into consideration how much horsepower your engine has before using an automatic trans. By nature, the front pump of the automatic transmission uses some available horsepower to run. If you are using a stock engine, you’ll have very little horsepower left to drive the car. Removing the heavy stock flywheel also means less available torque at low RPM’s. The stock flywheel delivered quite a bit of torque via inertia (rotational force). This kit works best with a modified engine.


In the end if you want an automatic a Pinto 2.0 or 2.3 with trans may be the best bet since the engine has enough HP to overcome the loss with an auto.
 
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Phil Brown said:
Seem to remember years ago someone used a Dodge or Chrysler auto trans in an A with good success. The reason for that trans was its compact size.
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Yes, and the 904 out of a Slant 6 is great because of the Slant 6 starter location is very similar to the Model-A starter location.

Steve Becker at Bert's had a complete Model-A 904 transmission conversion set-up for sale at one time. He likely has sold it but he may be able to get another one.
 
IMHO, converting to an automatic takes so much away from the Model A driving experience that it no longer is a Model A. I understand that physical limitations come into play and that one would want to continue in the hobby even after one is no longer able to shift a manual transmission, but why ruin an original Model A? I believe Shay replicas were available with auto trannies. Again IMHO, the Shay replica would be just as much a real Model A as a Model A where the ****** was swapped out for an automatic.


There's one on ebay now: https://www.ebay.com/itm/1662004466...btjGUqc/88nLK7SOAq3BN9BQ==|tkp:Bk9SR8ij8oOxYg
 
Will N said:
IMHO, converting to an automatic takes so much away from the Model A driving experience that it no longer is a Model A. I understand that physical limitations come into play and that one would want to continue in the hobby even after one is no longer able to shift a manual transmission, but why ruin an original Model A? I believe Shay replicas were available with auto trannies. Again IMHO, the Shay replica would be just as much a real Model A as a Model A where the ****** was swapped out for an automatic.
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For me, If I could no longer shift gears, a Model A with an automatic but otherwise mostly stock would be MUCH better than a Shay with the odd-looking wheels, juice brakes, not-quite-right body, and not-even-close engine sound.
Put on a HC head to help offset the horsepower drag of the automatic.
 
goldeneagle said:
Why?
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While I can' speak for the OP, IMHO the "why" for an automatic transmission can be 'justified' for many reasons in today's society. "Why" do some feel the need to convert to 12 volt electrical systems? "Why" do some feel the need to convert from Babbitt to Insert Bearings?? "Why" do we feel the need for automatic advance distributors??? "Why" the need to change to different F100 steering boxes, electronic ignitions, carburetors, 16" wheels, or (you fill in the blank)????

What some may feel is a valid excuse may not be as valid for someone else. Think about it, how in the world did a handicapped person ever manage to drive a Model-A back in the 1930s?? :confused: ;) :p
 
when i was rebuilding a ZF transmission for a Peugeot 404 wagon it seemed like a good starting point for a automatic for the A, it’s short, has a removable bell housing and has torque tube drive
 
There's probably many good Auto transmission options that will work in a model A. The GM powerglide looks like a good option because of the low drag to operate it. I would not recommend it for an A though because it's a two speed trans. 1st gear can really wind out before shifting into high. That's why drag racers like it. The GM TH200-4R is about the size as a powerglide and has a very low drag but same bolt pattern on the bellhousing as the powerglide. 4 speeds means keeping the A engine in the low rpms and overdrive is .67:1, so it's like having a Mitchell for highway cruising.
 
If it means I can continue to drive my Model "A" while in my late 80s, I would gladly have an automatic transmission installed.
 
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