Flathead

Flathead

Friday, September 30, 2011

Shortening a Torque Tube





I f you are building a vintage ride like I am, you probably want to go with a closed drive line.
When you hear the term "closed", it means the driveshaft is enclosed by what is known as a torque tube. The torque tube bolts from the transmission mount on the K member to the rear end and the rear radius rods attach to it.

You can convert to an open drive line with these cars by either using a truck banjo rear end with an open end or buying a kit Speedway sells to convert a closed drive line Ford banjo rear end to an open drive line. Then you'd have to have a driveshaft built and you'd need a truck transmission to bolt it to or if you were using an automatic transmission, you'd have to figure out what universal joint yoke you'd need for that transmission.

But, to keep the car period correct, I'm using a '36 Ford torque tube that I am cutting down to fit between the rear end and the transmission mount. Why do I need to cut down a torque tube? You may not if you are using a stock 1932 Ford banjo rear end but, those rear ends are basically Model A rear ends and are very weak compared to later banjo rears. Plus, a '32 rear end has a pinion shaft that is part of the driveshaft. Mine was missing the pinion shaft and to buy a set of matching pinion/ring gear was way more than finding a later flathead Ford rear end and shortening the torque tube & driveshaft.

So, I found a complete banjo rear end off Craigslist for $250! I mean everything was there, drum to drum, radius rods, rear spring, and it even had the speedometer gear on the torque tube. I had the entire chassis media blasted and then I had a flathead restorer rebuild the entire rear end. It should be bulletproof! But, I still need to shorten the torque tube.

To do this, you need to completely assemble the rear end and put it up on wheels, preferably the wheels you will use in the final build along with the front end on wheels so that you know exactly how the car will sit on the ground. The rear end will sag forwards so you will need to get a scissors jack to put under the rear end to level it.

What I normally do is get a piece of pvc pipe or a long round wooden dowel to put temporarily between the coupler on the banjo to the U joint on the transmission and eyeball it to get it level. Make sure you have the torque tube bell on the transmission, that is important! That's how the car will be going down the street pretty much once the torque tube is bolted together.

The length that you come up with for the distance between the coupler & the U joint is the distance you'll need the driveshaft shortened down to. I used a '46 thru '48 Ford driveshaft which is the same diameter all around, this makes it easy for a driveshaft shop to cut and re spline or cut and re weld it. You can't cut & re weld the tube type of driveshaft found on '36 Fords. Leave those for guys to make headers out of! You can also get a '34 Ford driveshaft and cut the 10 spline end off that attaches to the banjo and use a 6 to 10 spline adapter turned down in a lathe and then welded into the drive shaft. But I would have a driveshaft shop do the welding and have it balanced.

Okay, now once you have the chassis mocked up with something simulating the driveshaft take out the mockup driveshaft and put the torque tube onto the bell on the transmission mount and then put the back of the torque tube next to the rear end as close as you can get it to where it'll be bolted. You may want to get a couple of jack stands to hold the torque tube in place, it's much easier. Now measure the distance from the front of the flange on the banjo to the tip of the torque tube. That should give you your distance and mark it on your torque tube. I can't tell you exactly what it is because it's different for every car. Even if you were using the exact same parts, you might get a measurement that is off by a half an inch.

Now get out your chop saw and cut it but only cut it where the diameter is constant! That is very important. Then cut it again taking out how many inches you need to make the torque tube fit in the '32 frame. After it's cut, you should be able to join the 2 pieces together and they should mate up perfectly if you cut it straight. Use jack stands to hold everything where you want it and tack weld it in a few spots. I always take the torque tube back out and stand it up straight on the ground on the end with the flange to make sure it's level. You can even check it with a level on top of the torque tube while it's standing on end. If it's good, finish welding it together and than grind and smooth or just leave it if you want the raw look.

Now you can take that drive shaft and measurement to a reputable shop and have them shorten and re weld it together and balance it. Or, if you can find a place that can re spline it, it won't need to be balanced.

1 comment:

  1. Hey I would love to ask you some questions about steering options for your 32. I am running into issues with mine and need to figure something out, could you email me??

    ReplyDelete