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Old 11-29-2021, 12:30 AM   #1
SoCalCoupe
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Default 1941 Ford Open Drive Conversion

Did a search on "1941 Ford Open Drive Conversion" and found next to nothing. Sounds like the '41 Ford is an odd duck with some unique parts.


Understand that the radius rods, are too weak to function without a torque tube or torque arm.


Was looking for a bolt in, or even a weld-in, kit to connect the radius rods and a new torque arm to a pivot and weld that to the frame. Found nothing. Of course, I could make my own but then I would not have the advantage of anyone else's experience.



Found a couple of recommendations for ladder bars which I presume also require a panhard bar. Sounds more complicated than a radius-rod/torque-arm pivot.



Motivation is to run a T5 or Tremec 5speed. I've read dozens of posts on this conversion. To me, sounds overall easier to do an open-drive conversion than to mate the T5 to the torque tube.


Your thoughts on 1941 Ford open drive conversion.
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Old 11-29-2021, 02:28 AM   #2
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Default Re: 1941 Ford Open Drive Conversion

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Originally Posted by SoCalCoupe View Post
Did a search on "1941 Ford Open Drive Conversion" and found next to nothing.

Was looking for a bolt in, or even a weld-in, kit to connect the radius rods and a new torque arm to a pivot and weld that to the frame.

Motivation is to run a T5 or Tremec 5speed. I've read dozens of posts on this conversion. To me, sounds overall easier to do an open-drive conversion than to mate the T5 to the torque tube.

Your thoughts on 1941 Ford open drive conversion.

Hey SoCal ......Can't blame a guy for wanting to shift gears with a newer technology transmission in an old Ford...I can relate! Believe it or not, a friend and I have actually converted a torque tube to a T5 in a '35 Ford with an 8BA flathead engine. Click on the link BELOW if you have any interest in reading the full thread with pictures and details on that project.

https://www.fordbarn.com/forum/showt...T5+TORQUE+TUBE


If you have not realized the benefits of a correctly-installed (geometry-wise) banjo rear end, spring and supporting radius rods/torque tube, then there is still one good, proven path for you to take with your project, and that is to go ahead and install a preferred rear end using one of the well-proven installation kits like the one offered by "Chassis Engineering" utilizing a pair of semi-elliptical springs just like you might find in an everyday '55 Chevy or '67 Camaro. The kits are well-engineered, simple to set-up, and won't break the bank. That way, you don't have any guessing to do as far as modifying/reinforcing and correctly-articulating a banjo rear end in your '41. See the link BELOW! DD

https://www.summitracing.com/parts/c...+5cb4a9ba25bce








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Old 11-29-2021, 09:07 AM   #3
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Default Re: 1941 Ford Open Drive Conversion

The Hot Rod Works has a torque arm kit and a radius rod mount set up for the pre-1941 "long" radius rods to three point the system but I'm sure it would requires some mods to make it a better set up. If I went the torque arm route, I'd likely design and build my own set up. I like the simplicity of the buggy spring suspension so I'd either go that route or modify the T-5 for a torque tube drive as previously mentioned.
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Old 11-29-2021, 04:53 PM   #4
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Default Re: 1941 Ford Open Drive Conversion

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The Hot Rod Works has a torque arm kit and a radius rod mount set up for the pre-1941 "long" radius rods to three point the system but I'm sure it would requires some mods to make it a better set up. If I went the torque arm route, I'd likely design and build my own set up. I like the simplicity of the buggy spring suspension so I'd either go that route or modify the T-5 for a torque tube drive as previously mentioned.

Ah YES ...."THE SIMPLICITY OF THE BUGGY SPRING SUSPENSION"! You almost couldn't say it any more simplistically. But there are a lot of "modifiers" in our ranks that still do not understand the totality of that simplicity. There are two basic elements that must be remembered when evaluating just how Henry's "buggy sprung, torque tube system" actually works, and what is required to remain fully, and safely functional.

The first element of the system is that the whole rear end/torque tube assembly articulates about TWO points in two dimensions. The assembly is able to ROLL about the longitudinal axis defined by the point in the center of the rear crossmember where the buggy spring is securely clamped, in addition to the front end of the torque tube assembly joint approximating a point slightly in front of the torque tube bell, essentially in line with the center of the U-joint.

The REAR end of the whole assembly is able to move up and down in a PITCHING motion via buggy spring action and constraint, about the same point at the front end of the torque tube and center of U-joint as discussed above. The 'captured ball' surrounding the U-joint at the front end of torque tube serves to anchor-securely that end of the torque tube, yet allowing full articulation about that point in the center of the U-joint.

The SECOND element that is often overlooked is that the TORQUE TUBE is the member which transmits the driving force that moves the vehicle forward, or rearward in the case of reverse. The torque tube actually pushes the vehicle forward, and pulls the vehicle in reverse. The torque tube is also the member that resists any control over the rear axle housing's propensity to twist upward at the front while transmitting torque to drive the vehicle FORWARD. While driving the vehicle in reverse, the axle housing tries to twist downward in the front. This "torque-induced" movement is normally contained and controlled by the torque tube. Once the torque tube is eliminated, as in an 'open-drive-conversion', those two radius rods (formed from rolled sheet-metal) now have their work cut-out for them trying to control the TORQUE-rolling of the rear axle assembly. You've gotta remember that these two wimpy rods are now what is left to PUSH the vehicle forward, or pull it rearward as in REVERSE. And if you 'GET-on-it' hard, all bets are off! Those radius rods can fold-up like spaghetti. They were originally designed ONLY as a means of reinforcement for keeping the TORQUE TUBE at an angle of 90 to the banjo housing, via simple triangulation.

Many times when modifying an old Ford's torque tube system to subsequently perform "open-drive" duty, some of these elements are overlooked, or even totally mis-understood. If the modified system overlooks any element of the original design, the vehicle will likely drive like crap, especially when traversing odd changes in road height, like driveway entrances, and pot holes. And heavy acceleration can be especially destructive if rear axle torque is not adequately controlled by substantial members specifically designed for that function. The entire rear end suspension must function in it's entire range of movement just as well as a stock torque tube rear end.

One more thing usually seen during these modifications is radius rods being "split", spread-out, and anchored to a frame rail by a bracket of some kind. In a case like this, whenever the rear end (or front axle) is raised or lowered at one end, as if you drove one rear wheel into a deep pot hole, anything that causes the rear end (or front axle) to ROLL in alignment with the longitudinal axis of the vehicle, you are actually TWISTING those radius rods. They are only going to 'TWIST' so many cycles before they break or fracture at a mounting point, or anywehere along their length. This does not occur when the radius rod is mounted to the torque tube. NO COMPONENT gets twisted with the normal movements in a torque tube rear end assembly. If you don't understand ANY of the above, trying to SUCCESSFULLY MODIFY a torque tube system to function properly is likely not going to end well. DD
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Old 11-30-2021, 09:27 AM   #5
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Default Re: 1941 Ford Open Drive Conversion

The Hot Rod Works set up uses a Heim end mounted just under the transmission output that can swivel as well as rotate on the spherical ball but the Heim end looks kind of small and they mention welding the center torque arm somewhere on the two "long" type radius rods. I would use my own radius rods and arm fabricated from better tubing and a beefier bracket & Heim end. That torque tube is nice and beefy for a reason and replacing it with something less may not be the way to go. That rear axle has to move in roll axis as well as in the up & down vertical arc axis for it all to work like Ford made it. If there is a bind in it anywhere then it won't work right.
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Old 12-01-2021, 12:24 AM   #6
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Default Re: 1941 Ford Open Drive Conversion

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Quote:
Originally Posted by rotorwrench View Post
The Hot Rod Works set up uses a Heim end mounted just under the transmission output that can swivel as well as rotate on the spherical ball but the Heim end looks kind of small and they mention welding the center torque arm somewhere on the two "long" type radius rods. I would use my own radius rods and arm fabricated from better tubing and a beefier bracket & Heim end. That torque tube is nice and beefy for a reason and replacing it with something less may not be the way to go. That rear axle has to move in roll axis as well as in the up & down vertical arc axis for it all to work like Ford made it. If there is a bind in it anywhere then it won't work right.
Guys, thanks for all the ideas. I have searched and read through V8COOPMAN's threads on t5 to torque-tube conversions. It's very impressive.


I think though that my preference is to go with an open drive solution. I'd really like to do one just like the "Hot Rod Works set up uses a Heim end mounted just under the transmission output that can swivel as well as rotate." Was hoping someone had used that kit and had some experience adapting it to a '41. Wrote to Hot Rod Works and they recommended ladder bars.


My end goal is to have a T5 and some slight engine improvements on the flathead, higher compression heads and either a bigger carb, two carbs or EFI.



I'll stay original or period correct where I can because that's the fun part but I don't mind going with invisible improvements. I want to do the work myself just for the satisfaction but don't want to do more work than necessary. For example, I'm still 6 volt and have no plans to change unless a decision for EFI forces my hand.


Don't know the advantages/disadvantages between staying with a banjo rear rear end, correctly sprung, or going with a newer 8" Ford. My experience is with 1960's Chevy's. Want to learn something new.



Starting work is still several months into the future, just collecting ideas
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Old 12-01-2021, 12:14 PM   #7
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Default Re: 1941 Ford Open Drive Conversion

I assume this is a street rod? With that said them, the weight of the rear axle will determine the ride quality od the vehicle. A heavy 9" will ride somewhat like a pickup truck, so something like a Spicer/Dana 35 is all you need. Common in Jeeps which is quite narrow, however they were also found in some Jeep Grand Cherokees. Some of these have a triangulated rear suspension. I used a Jeep with wheel spacers.
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Old 12-01-2021, 03:09 PM   #8
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Default Re: 1941 Ford Open Drive Conversion

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I assume this is a street rod? With that said them, the weight of the rear axle will determine the ride quality od the vehicle. A heavy 9" will ride somewhat like a pickup truck, so something like a Spicer/Dana 35 is all you need. Common in Jeeps which is quite narrow, however they were also found in some Jeep Grand Cherokees. Some of these have a triangulated rear suspension. I used a Jeep with wheel spacers.
Gramps

Ol' Ron .....You must know something that I'm overlooking, because you keep alluding to how much heavier a Ford 9" rear end is when compared to the Jeep/Dana 35. Sounds like an old wives' tale that has been carried forward for at least a couple of decades now. So ....looking at this BLACK '57 Ford 9" rear end, and comparing it to the rusty-looking Dana 35, Does the "35" really look a whole lot LIGHTER than the Ford 9" to you? Has anyone weighed the two for a difference? Plus ....that Dana sure is UGLY! DD


DANA 35




'57 Ford 9"





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Old 12-02-2021, 09:13 AM   #9
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Default Re: 1941 Ford Open Drive Conversion

Pretty useful information, had to re read it a couple times to understand it all lol. thanks
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Old 12-02-2021, 11:11 AM   #10
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Default Re: 1941 Ford Open Drive Conversion

I think Spicer/Dana manufactured the AMC 7-9/16-inch (AKA AMC-15) for light duty 4 and 6-cylinder application back in the late 60s. When Spicer/Dana put their own designation to it then it followed their normal torque load rating system. It became the Dana 35. Torque load rating would be 3,500 ft/lbs. The Dana 41, 44, 45, & 53 all follow this rating system.

If it is a bare housing with spring pads only then it likely is a fair bit lighter than the Ford 9-inch. They are available in narrow configurations so someone that just wants a narrow driver rear axle assembly to fit an application like an old Ford could use it. They sometimes have some odd ratios but AMC used it for both 2WD and 4WD applications and Chrysler/Jeep/Eagle likely followed suit for a time.
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Old 12-02-2021, 11:59 AM   #11
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Default Re: 1941 Ford Open Drive Conversion

The 35 has another advantage, it's much cheaper. I have nothing against to 9". used one behind my Hemi Dodge, back in the 70's. Don't notice any ride difference, however, The Dodge was a heaver car, and that IZ the difference. I can weight he 35, but not the 9" because I don't have one. While on the subject of rear axles the Dana 44 is a nice strong axle, comes from the Jeep grand Cherokee. Comes with posi and is also very inexpensive. As a builder I don't have nuch cash on hand, However SS has given me a raise so that will help. THe cost of building things is getting very expensive. I'm sorry I sold my boring bar because I have to bore a block and fit the pistons. I put money asside every month to cover the cost. Several shops that did good work have closed their doors. I asked one shop to bore my block, and was told I can't take .125" out of the block and he wouldn't do it/ I found a Shell molded flathead crank I'd like to have ground to usr "H" beam rods and there isn't any one here in vermont that does that anymore and have to send it down to Mass, so trust is a big issue. Many of you guys have extra funds that make this Hobby continue, but . not for long. Check the price og alum heads and a Offy 4bl intake can't be found anywhere, it's on back order.
I enjoy this Hobby because I like building as much as I can. Made my own front disk grake system. Much lighter that the aftermarket ones, and cheaper. Hope it works.
I understand they won't be building any gas powered cars after 2130 all electric after that, sad day for the flathead, have to make our own fuel.
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Old 01-07-2022, 10:28 AM   #12
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Default Re: 1941 Ford Open Drive Conversion

Looks like a person could "keep it simple" and use the original banjo rear end with the Chassis Engineering kit, convert to open drive and be good to go. In other words, no new rear end.



Quote:
Originally Posted by V8COOPMAN View Post
Hey SoCal ......Can't blame a guy for wanting to shift gears with a newer technology transmission in an old Ford...I can relate! Believe it or not, a friend and I have actually converted a torque tube to a T5 in a '35 Ford with an 8BA flathead engine. Click on the link BELOW if you have any interest in reading the full thread with pictures and details on that project.

https://www.fordbarn.com/forum/showt...T5+TORQUE+TUBE


If you have not realized the benefits of a correctly-installed (geometry-wise) banjo rear end, spring and supporting radius rods/torque tube, then there is still one good, proven path for you to take with your project, and that is to go ahead and install a preferred rear end using one of the well-proven installation kits like the one offered by "Chassis Engineering" utilizing a pair of semi-elliptical springs just like you might find in an everyday '55 Chevy or '67 Camaro. The kits are well-engineered, simple to set-up, and won't break the bank. That way, you don't have any guessing to do as far as modifying/reinforcing and correctly-articulating a banjo rear end in your '41. See the link BELOW! DD

https://www.summitracing.com/parts/c...+5cb4a9ba25bce








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Old 01-07-2022, 12:52 PM   #13
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Default Re: 1941 Ford Open Drive Conversion

The other thing to think about is to ponder what rear-end ratios would be the best - given your final over-drive ratio of the T5. Then things like rebuilding the brake systems, etc..

I've rebuilt/setup both banjo rears as well as 8" and 9" Ford stuff. One VERY nice thing about going to a later 8" Ford is the huge availability of gears, differentials, axles and brakes. Not only are almost all of the parts cheaper, but they're also available all over the place. Things like axles, bearings, wheel cylinders, brake drums, rear hubs, etc -- can get mighty pricey if you need to purchase them for your ole' banjo rear.

Ladder Bar Supports and Welding on Rear End Housings: Lots of folks will weld all sorts of brackets on rear end housings - but never check/re-align the housing alignment after the fact. When you weld things like spring hangers and ladder bar brackets on one-side of the housing, you'd be surprised how much the housing will "move/shrink" on the side you are welding on. Then imagine how far out of alignment your bearings/hubs are as a result. For this reason, when I am building an 8" or 9" rear, I start with either a wider one (assuming I'm going to shorten the width or a new housing unit without the bearing/brake flanges installed. After ALL the welding is done (and sometimes heating/shrinking for straightening) for things like ladder bars, spring hangers, caliper brackets, Panhard bars, etc. - THEN I use an alignment bar and weld in the bearing flanges on the outsides. And if I don't have the necessary alignment stuff - then I bring it to a shop that does and specializes in rear end custom work.

The reason I bring the whole welding/alignment issue up is because there are many shops that have the equipment to work on 8" and 9" housings to do the above work properly (alignment bars, bearing pucks, etc) - but try to find one that actually does this with early Ford banjo rears? Most guys just weld away . . . without thinking about how alignment issues can cause bearing, axle and hub issues on any rear end - let alone a banjo Ford.

If I was going to the trouble of converting to open drive, I'd seriously think through ALL the components I need - before making the decision. I'd probably go the 8" route unless I had a huge 'vintage/traditional' itch to scratch.

Best of luck . . . many ways to skin this cat!
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Old 01-07-2022, 05:34 PM   #14
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Default Re: 1941 Ford Open Drive Conversion

I use to buy surplus mail dispatcher jeeps just for the goodies , the front straight axle , the dana posi rear , steering column and wheel , shifter and e brake . All look the part for a 30-40 ford . The rear axle ratios were anywhere from 273 to 411 and very narrow . The earlier ones even took 51/2” x5 wheels ( jeep center diam is karger than ford )
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Old 01-07-2022, 05:59 PM   #15
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Default Re: 1941 Ford Open Drive Conversion

Just a question. Is the frame behind the original transverse spring mount strong enough to take the loads of a parallel spring set up?
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Old 01-07-2022, 07:01 PM   #16
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Just a question. Is the frame behind the original transverse spring mount strong enough to take the loads of a parallel spring set up?

STILL not sure yet......ONLY a couple of billion of them running up and down American roads for years now. SERIOUSLY .....plenty strong, +! DD
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Old 01-07-2022, 08:17 PM   #17
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Just a question. Is the frame behind the original transverse spring mount strong enough to take the loads of a parallel spring set up?
Yes it is strong enough. I've been around this stuff for a long time and I've yet to see a failure of the Ford frame using a parallel leaf spring kit. Manufacturers put a lot of engineering into what they make and factor safety into the equation The last thing they need is bad publicity and a lawsuit.
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Old 01-08-2022, 10:36 AM   #18
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Default Re: 1941 Ford Open Drive Conversion

Thanks for answers.
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Old 01-08-2022, 12:26 PM   #19
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Default Re: 1941 Ford Open Drive Conversion

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Just a question. Is the frame behind the original transverse spring mount strong enough to take the loads of a parallel spring set up?
Lots of these setups have been done for years - have not heard of issues for typical street cars. I have a custom setup on my off-topic 32 three-window - 9" rear, parallel leaf springs, 500+ HP SBC - the rear frame rails are boxed for added strength. One can always box the rear frame areas and tie the plates into the rear cross-member . . . adds a lot of strength.

If you're doing this type of frame/suspension work, sure is nice to pull the body so you can get to all the areas you're working in - making all the fabrication and welding a LOT easier and producing a better result in the end. You will probably find that the time spent on pulling the body will be well worth it when you're doing the rest of the work.

I've done it both ways . . . body OFF is far superior in all aspects of the job and final product.
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Old 01-09-2022, 10:36 AM   #20
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Default Re: 1941 Ford Open Drive Conversion

Thanks, that's the part I wondered about, since the factory boxing stops aft the buggy spring mount.
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