Maybe it's the long days I have been putting in, or maybe it's the all the holiday festivities going to my head, but I find myself with a real head scratcher. The rear, TT, drive shaft, universal, and rear trans mount all came as an assembly. I can only assume out of a car that at one point was driving around. I pulled everything apart, triple measured and shortened the TT, assembled everything and it fits good. I figured that if all the parts worked together at length "A" then if I removed the exact amount from the tube and the driveshaft I would be set.... Wrong... thats what I get for thinking on my own...lol Before I go and remove more from the shaft can anyone explain how my logic was so flawed? After removing equal parts from the TT and drive shaft, the shaft is still to long, by about an inch. What the heck am I missing here? Thanks. *** Edit*** Does the drive shat protrude into the center of the U-joint? Is the groove on the shaft supposed to be flush with the back end of the u-joint? That would give me the inch, but would the speedo gear still fit (I don't have the speedo gear yet) Chappy
I agree , your math should have worked. Generally speaking, the shaft will end up about flush with the bell end of the TT, maybe a 16"th or so short of flush. If you have put it together so you know for a fact the tube is correct, then I would assemble the stuff on the front of the shaft, Thrust washer, bearing, speedo gear, snap ring, slip it all in the tube and see what it looks like at the back, then do the math to correct it. Are you planning to cut splines, or weld it into the coupler? Also, the front bearing surface is important, clean it up with some very fine sand paper and lets see what the surface looks like
Thanks for the info. The plan is to turn down the shaft and the inside of the coupler until I have a press fit. Then I will drill and put the pin in and weld the pin in place. Then weld the coupler to the shaft, and possibly also add a couple of plug welds. I figured i would polish the bearing surface while I had it in the lathe. It looks worse In the pictures than it actually is. Does anyone have a picture of the drive shaft installed in the u-joint with the speedo gear, thrust washers and clip in place? Thanks again Chappy
Interesting, I would of thought the same myself, shorten the TT to your required length, do the same to the drive shaft and you’re done. Hindsight is wonderful, check the original measurement between the TT cup and end of drive shaft and make sure they are the same after your mods.
I don’t know what year assembly you are playing with but this is an A model assembly, as you can see the shaft finishes approximately a 1/16” below the edge of the cup. Hopefully these are some use to you. I
When you measured the tube did you have the round cover that goes over the u joint in place? The one that the torque tube pivots on. I cant remember what its called but you need that in place. Ive done this a few times. I always have the driveshaft resplined myself but sounds like youve got it under control
I would think the easiest way to do this would be to fit and tack weld the torquetube first. Install the uncut driveshaft in there, and measure how much is sticking out. Them modify it so it is exactly that much shorter. That MacroMachines kid on YouTube has a great video on cutting new splines on an old Ford driveshaft with a mill and simple indexer. No welding on the driveshaft required. I'm going to use his math and methods next time I have to do one.
From my experience and measuring an untouched '36 TT and driveshaft the driveshaft butt was .0130 inboard of the bell. This is how we set mine up with the driveshaft 1/8" shorter than the torque tube. At this setting the speedometer drive gear has about 1/4" of travel (wiggle room) between the retaining clip and thrust washer and syncs up nicely with the speedometer drive once its installed.
yes, when I cut the TT I had the cup and clamp in place and after cutting, the TT fits nice. its just so strange that every worked correctly at stock lengths but removing the same amount from the both parts makes it not work...lol. I can make it all work, I just can't get my head around why the simple logic failed....or, how i failed the simple logic...lol. thanks Chappy
Thanks Alchemy, I will check out the video. I get how measuring the parts and doing the math would be needed if you were working with a drive shaft and TT of unknown origins that had never "worked" together. You would certainly want to measure twice and cut once. But I can't for the life of me figure out how simply removing equal amounts of material from the middle of two parts that worked together successfully results in them not working together. thanks for the input... it's most helpful. Chappy
Thanks for the pics, I am not sure I understand your 1/8" shorter comment. For this statement clarification we can say that the driveshaft butt is even with the end of the Bell. In this configuration my driveshaft would be around 4 inches shorter than my TT (sorry I am not at home to get an exact measurement) as the TT extends past the end of the driveshaft to cover the coupler and pinion shaft. Sorry if I am being dense on this. Chappy
The stick out length of the drive shaft is not critical at all. There is plenty of spline engagement with out worrying about 1/4” The thing that needs addressed is clearance on the speedo drive gear. It needs to have about 1/8” axial clearance. I measured four stock rear ends and that is what I measured. The position of the retaining ring groove determines where the drive should be vs the torque tube.
The torque tube (housing) must be aligned absolutely perfect when shortened. If not absolutely perfect there will be constant movement where the back end of the driveshaft , with internal splines, fits over the splines of the pinion gear. The result will be the splines, usually the internal splines, will wear out. Big tears will result as the car will cease to move. speedshifter Greg w
I’m confused here, if you removed say 4” from the TT and the Drive shaft in the middle of the TT area, then tacked the 2 together nothing would change at either end , that appears to be a fact. This is just pointing out that nothing would change. You obviously wouldn’t do it like that though as the drive shaft would just shear at its weld point. At the end of the day, this is an unmodifed standard assembly so as long as the dimensions between the the shaft and cup are kept the same and the mods are only done at the diff coupling end your speedo area remains the same. The only area where confusion could possibly happen regarding the length is allowing for the splining of the shaft or the machining for the coupling sleeve.
I made two tools when I shortened my torque tube. I made a disk and welded on the end of a new piece of pipe. I machined it flat to the pipe. I machined a coupling to just fit in the collor in the trans end. This allowed me to make sure the torque tube rear flange was square with the other end. I had replaced it because I was using a 34 tube and the bearings are different in a 40 rear.. The other tube was the other half of the pipe with a machined end to just fit in the trans end of the tube. It stuck out the rear end end. I rolled the tube on the flange sides and worked on the end to have the pipe to dangle the same on all flange sides. This made sure the trans end was right.
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