Well nobody seemed too interested in this but I just feel like writing it down today... I didn't take too many pics when I was doing it because I needed to concentrate on what I was doing (also I wasn't sure how it would turn out ) So you're building a traditional Hot Rod... You have the right motor (cough-flathead-cough, cough)... You have a 39 toploader (Or if your real crafty, a column shifter)... And you have a banjo rear (stock or quickie)... So now all you have to do is find an old truck to get the open-drive parts, have a drive shaft made, and fabricate some trailing arms and a panhard, right?!??? Not so fast, Speedy! Now say you got the rear and trans out of a 39 car and you HAD to take the torque tube (you will need the 40-Ford driveshaft that goes with the tube) with it.... Well then you have all you need to be period correct and on the cheap at the same time! How about keeping the TUBE!?!?!?!? 'No Way,' you say... 'Can't be done' you say... 'I wear girly bits' you say.................. Well, I might be able to help you with SOME of what you got going on there, Sport. Just keep away from me whilst I do it.... Let's get started... What you need: A: Fairly complete frame with most things dialed including motor and trans mounts and rear location B: Banjo rear completely assembled with guts C: Early ford three-speed trans case with mounts for torque tube. D: 40 Ford style torque tube and shaft with the solid shaft and center and front support bearings in the tube E: The usual welding and cutting tools and skills 1. FIRST thing you need to do is get your engine and trans bolted together and mounted in the frame at ride angle... Set up the front and rear suspension how you want it and get your rubber on there and set the motor at level with the frame at ride height and angle... 2. Now you need to mount the BOTTOM cup on the back of the trans that catches the Front of the tube... You will use this to make your measurements for the length of the tube. 3. I think the BEST way to do this is to take the rear spring off the rear at this point and temporarily 'mount' the rear to the frame where you want it to touch at it's full upswing. Meaning that when your rear bottoms out, it will hit the frame at this point. I would also mount it so that you can swivel the yoke up and down slightly to point at the back of the trans. 4. Now it is time to Measure.... Measure A_LOT! Measure every conceivable way that might affect the length of the tube... What I did was set the front of the tube into the bottom cup-mount that you mounted to the back of the trans in step 2. Then I made sure it was back as far as it could go in the cup and still be 'fully-engaged' and I marked both sides of the cup where the front of the flange on the tube rested in the cup. Next, I measured from those marks back to the flange on the front of the banjo.... That should be your length for the tube. The only problem is that you may have other concerns that keep you from measuring it this way so just check and double-check what you come up with for the length of the tube... Then do it again. 5. NOW YOU MUST MEASURE THE "BEFORE" LENGTH OF THE TUBE!!! It's important to know that length the tube is BEFORE YOU START CUTTING! So put the hack-saw down, Sport... Measure the tube and write the length down somewhere it won't get lost... I cleaned up a spot on the tube itself that I was reasonably certain wouldn't get cut off and wrote "Was ???" because I loose stuff... 6. Now identify the orientation of the back flange (mounts to rear) to the tube. You will notice that there is a 'Drain-Back' groove in the flange that allows the rear-end lube to drain back to the rear through a hole in the banjo... Make sure you identify this and you don't get it miss-aligned... It doesn't really matter how the tube gets mounted up to the flange as you can fiddle with the wishbone mounts etc... But I marked the spot on the flange where the weld seam on the tube hit, just because I like to keep it as much like Henry had it as possible... I also plan on using Ford gauges and want to retain the cable-driven tach so the mounting location for that needed to stay put. I also like where the grease fitting for the center bearing in the tube was and wanted to keep it there. 7. Now you can cut the flange that meets the rear end off the tube... I used cut-off wheels with the flange face as a guide so that I could make the cut as consistent as possible. I ended up with a PERFECT 1/2 inch thick flange... This made measuring and math easier later. 8. So now you can just cut the tube to the length you found in step 5 and weld it all up right? SLOW DOWN there Ricky-Bobby... There are a few things to consider before you make the cut that removes the "APPROPRIATE" amount of tube... a. you need to subtract the thickness of the flange b. you also need to subtract the gap you are going to leave to allow for weld penetration... (The tube is about 1/8" thick so I left a 1/8" gap for penetration.) c. NOW HERE IS SOMETHING FOR DEBATE... To my way of thinking, I wanted there to be a little backward pressure (caused by the rear spring) on the front mount of the tube That way the tube wouldnt want to slide forward in the mount and cause a leak or rattle or anything like that. So I took out another 1/8 to ensure the rear spring would hold the tube against the seal in the cups that mount it to the trans. Does this make sense or am I an idiot? 9. Now you can cut the tube to length Again, try to make the cut as even and consistent as possible so that you dont have to grind it even later. If you have one of those band saws like they have at the scrap yard, you are probably golden 10. Now you can check the length I hope it turned out OK!  11. Here comes the tricky part How do you get the tube mounted to the flange so that the tube is not off-center to the flange? Well, step right up and Ill tell a tale, a tale of a fateful . a. Mount the flange to the banjo Make sure the drain-back groove is pointing down and that its mounted pretty solid to the rear. b. Now you need the drive shaft that came with the tube Mount the shaft with the coupler to the rear yoke. c. Lube up the shaft and slide the shortened tube down over the shaft, through the center and front support bearings in the tube. d. Now you can set the gap between the tube and the flange with some sort of spacer, and try to position it so that you dont feel the tube resting too much on either the front or middle support bearings e. Tack it up Try not to get a bunch of slag on the shaft or the yoke or exposed bearings in the rear. And, try to tack it fairly solid so that it wont crack apart when you test the length again. 12. Remove the tube and the shaft and reattach the tube to the rear and see if it aligns with the cups on the trans. You will want to put the spring back on the rear and mount it up normally to check the tube. Remember, you might have to push a bit to get the tube to drop into the trans mount correctly. 13. If everything lines up right, pull it all apart and weld it solid I have a 120V Mig welder so I welded inside and out of the tube If you do this, make sure you grind down and excessive welds with a die-grinder and cut a groove for the drain-back. Make sure you have good solid welds. 14. Now you can remeasure the tube. Subtract the new measurement from the old measurement and the difference it the amount you need removed from the shaft. Id have a shop cut it and respline it. Just dont have them drill the hole for the pin in the rear of the shaft so that if you need a bit of wiggle room you can adjust the pin-hole yourself. That should do it Please THINK about all this stuff before you dive right in If anything doesnt make sense lets figure it out BEFORE you cut, cut, cut
Thanks for that. One question: is the drive shaft the same diameter all along its length - in other words , can it be just cut and resplined to any length? I plan on installing a '38/'39 axle and tube in a '34 chassis, and other people had suggested cutting and welding the drive shaft.
Yes it's the same diameter... That's the beauty of the 40 tube and I can't tell you the years that are the same... Maybe someone else can? I think people that recommend the cut/weld are thinking of different years.
Thanks for the Great Piece on this subject. I needed this. Also was wondering about the bearing inside. By shorting the drive does it change any balance in the unit? Thanks George
Hello, I want to resurrect this old thread with a question. Is a ‘40 Ford torque tube cast iron? I would say no. I shortened mine and put it in a temporary fixture for welding. I took it to a welder just to make sure it’s welded nicely, as I’m just an ok welder. The shop says it’s cast and won’t weld it. I don’t think that’s the case. Am I wrong? Thanks!
@Marty Strode : Thats how I do it too. However it always seems to pull out of true a little bit using a mig welder. I do it while chucked in the lathe with a steady rest so I can measure if it moved or not, but the lathe is not long enough to face the end and make it square again. Question is... do you think it pulls less using the tig welder ?
I agree, but if the mount face to the diff is not square the front end of the tube will be out of alignment and so will the shaft , no?
An old time machinist said you should assemble your shortened torquetube and driveshaft with no front bearing, then spin the driveshaft. You can see how straight they are if the driveshaft has a bend, or if the shaft stays straight but is offset a bit to one direction as it turns.
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