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Technical 1940 ford driveshaft shortening & respline

Discussion in 'Traditional Hot Rods' started by hydroshawn, Jul 22, 2015.

  1. hydroshawn
    Joined: May 27, 2006
    Posts: 335

    hydroshawn
    Member
    from Brenham,Tx

    Hey guys need some help!!
    I'm putting a 40 ford rearend in my AV8. I can do the torque tube but am looking for someone in the Texas area that I can send the drive shaft to to get shortened and resplined.

    So what length needs to be removed for both???

    Thanks in advance

    Shawn
     
  2. porknbeaner
    Joined: Sep 12, 2003
    Posts: 41,143

    porknbeaner
    Member

    Shawn,
    remove the drive shaft and install the torque tube empty to the rear, out your rear in place and then push the torque tube up where it needs to be. Cut it to length and keep track of how much you cut off and equal length will need to be removed from your drive shaft.
    Find a machine shop that can re-spline axles, they will have to have a horizontal mill and an indexing head. take them the shaft and tell them how much you need removed from the driveshaft.

    Done deal
     
  3. I did this to a '32 I had 4-5 years ago. What ever dimension I took from the tube, I took from the center of the shaft. I then had a "competent" machine shop weld it back together. (zero runout). Worked fine with no vibration.
     
  4. hydroshawn
    Joined: May 27, 2006
    Posts: 335

    hydroshawn
    Member
    from Brenham,Tx

    Thanks for the great info!
    I do have an "A" torque tube would I just cut and weld to the same length?
     
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  5. Kevin Lee
    Joined: Nov 12, 2001
    Posts: 7,401

    Kevin Lee
    Super Moderator
    Staff Member

    You're going to find that some driveshafts are a constant diameter and some are smaller between the splined and bearing surfaces. Makes shortening and resplining an issue. You're going to have to get it apart and see what you're actually dealing with.
     
  6. alchemy
    Joined: Sep 27, 2002
    Posts: 14,406

    alchemy
    ALLIANCE MEMBER

    The CL of the axle to the mounting surface of the torquetube (basically the length of the banjo) is not probably not the same on an A as it is on a '40. So, the answer is no. And the likelihood you placed your engine in exactly the same location as the stock A 4-cylinder is also not much.
     
  7. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,683

    Bruce Lancaster
    Member Emeritus

    Remember one parameter needs to be controlled at front...with all the hardware in place, roller bearing, thrust bearing, seal , speedo drive the driveshaft sets down agains all that to set front location against the thrust. That has to be gotten right, and might not all come out right if you do all your thinking at the other end.

    (Also...the dimension Alchemy mentions IS different '28-32, '32-34, and '35-48.)
     
  8. Mr48chev
    Joined: Dec 28, 2007
    Posts: 25,662

    Mr48chev
    ALLIANCE MEMBER

    A good local full service machine shop should be able to shorten the shaft and cut new splines. That's the machine shop that makes shafts for local industrial plants and farm or other equipment and not the machine shop you take heads or blocks to to have the machined.
     
  9. rockfish
    Joined: Apr 11, 2001
    Posts: 445

    rockfish
    Member

    I agree with Mr48Chev that most good machine shops should be able to respline for you. Also, I think you should stick with that plan versus cutting down the driveshaft in the center and welding back together. Cutting and welding will give you a shaft that's more likely to vibrate and/or break. It's done and will often work but if you're paying $$ and farming out the work go with cutting down and resplining.
     
  10. hydroshawn
    Joined: May 27, 2006
    Posts: 335

    hydroshawn
    Member
    from Brenham,Tx

    Thanks again for all the great advise! It really helped a lot!!
     
  11. Ralph Moore
    Joined: May 1, 2007
    Posts: 633

    Ralph Moore
    Member

    Have you thought about buying one of Speedways drive shafts? They come long and you cut/ weld to fit your torque tube.
    I put one in my AV8 and it works great. They are hollow and the splined end is welded to it.
    A little spendy, but probably no more than having an original resplined.
     
  12. hydroshawn
    Joined: May 27, 2006
    Posts: 335

    hydroshawn
    Member
    from Brenham,Tx

    Thanks Bruce and all! I will keep notes as I go thru this.
     
  13. verde742
    Joined: Aug 11, 2010
    Posts: 5,236

    verde742
    ALLIANCE MEMBER

    I am using stock Model A transmission in a stock location. I will be putting a 1940 ford rear end with A De-arched Model T spring on top of the axle.
    So, to not re-invent the wheel,, Can anyone tell me how much I should shorten the drive shaft tube and the driveshaft?..I will be getting driveshaft re-spline. Also to use stock radius rods at stock bolt on location on drive shaft, how much should they be shortened?

    Also does anyone have a diagram of how driveshaft goes back together? I bought a bunch of pieces.
    Thanks,
     
  14. verde742
    Joined: Aug 11, 2010
    Posts: 5,236

    verde742
    ALLIANCE MEMBER

    I am going to try to get info, So I don't have to put rear end in till it is ready to stay in..
     
    Last edited: Feb 29, 2016
  15. Glenn Thoreson
    Joined: Aug 13, 2010
    Posts: 78

    Glenn Thoreson
    Member
    from SW Wyoming

    Hot Rod Works in Idaho does this modification and probably has the specs on file. Good folks to deal with.
    Glenn
     
  16. verde742
    Joined: Aug 11, 2010
    Posts: 5,236

    verde742
    ALLIANCE MEMBER

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