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Technical Proper driveshaft length banjo rear and speedo gear

Discussion in 'Traditional Hot Rods' started by chiro, Oct 31, 2013.

  1. chiro
    Joined: Jun 23, 2008
    Posts: 868

    chiro
    ALLIANCE MEMBER

    Project is an AV8 with a flathead 59AB, closed '38 banjo and '38 3-speed toploader trans.

    I have shortened the torque tube and am preparing to shorten the driveshaft, or should I say have a new one built from the old ends of the former shaft.

    I want to run the Ford speedometer I have in the '35 dash I'm putting into the car. I will be using the stock worm gear that installs on the driveshaft and the "turtle" that bolts to the torque tube.

    I am assuming that the amount that the end of the shaft protrudes from the end on the ball cup on the torque tube is critical for proper alignment of the worm gear on the driveshaft to the gear in the turtle.

    Anybody know how much the driveshaft is supposed to protrude from the ball cup end of the torque tube in a stock setup so I can match it with the now shortened driveline to make sure the speedometer gears line up properly?

    Thanks,

    Andy
     
  2. F-6Garagerat
    Joined: Apr 12, 2008
    Posts: 2,652

    F-6Garagerat
    Member

    Wouldn't you just take the same amount from the shaft that you took from the torque tube? I thought you remove material from the shaft from the coupler end at the banjo pinion?
     
  3. Tank
    Joined: Nov 8, 2002
    Posts: 749

    Tank
    Member

    How much did you shorten the tube? Not to be a smart-ass, but however much you shortened the tube is how much you need to shorten the shaft.
    When I shortened mine I measured the overall length fisrt and wrote it on the tube, and cut it to fit and made a piece of tubing that tapped inside with a nice fit. I eliminated the bearing in this process also. Then welded it back together.

    For the shaft I cut all my length off the back of it. First I removed the 6 spline coupler off the end. Its held on by a rivet. I Drilled the rivet out, and saved the coupler. I then picked up the hole where the rivet was in a mill, and redrilled it the over the amount i wanted to shorten it. (This allowed me to bolt the coupler back on later). I chucked the shaft up in a lathe with a live center in the back end and a steady rest supporting the middle. I took a parting tool and touched off the end and put a deep cut the distance over that i shortened the tube. Then i took a turning tool and cleaned up the shaft where the coupler would go. Not much, just enough to clean it up. I cut the rest of the shaft off in a saw.
    Then i bored the end of the 6 spline coupler out to where it was a tap fit over the shaft. Bolted it back on with a grade 8 bolt, and then tig welded it to the shaft just for extra insurance.

    I have 0 vibration, and its worked well for me.

    To answer your question It is fairly critical, There is a snap ring that holds the speedo drive, a bearing, and a washer in place and all that goes against a spot on the torque tube. Thats what is "critical" in the front.
     
  4. chiro
    Joined: Jun 23, 2008
    Posts: 868

    chiro
    ALLIANCE MEMBER

    Yeah, shortening the shaft the same length as the tube would definately be the way to go IF (and I mean IF) the shaft was a STOCK shaft that came with the original rear. BUT, the shaft I have is an abortion. It's been shortened once before, didn't come with the rear and the shortening job was just horrible, with a really bad and ugly weld on it that I am certain would fail even if it was the proper length. So...the original question still stands as I can only really use the ends of the shaft I have to make up a new shaft with a new tube to proper length.

    So...anybody know how long the shaft is supposed to stick out of the end of the torque tube ball cup on a STOCK, un-shortened torque tube rear end?

    thanks,

    Andy
     

  5. 31ster
    Joined: Dec 26, 2007
    Posts: 215

    31ster
    Member

    I don't know if this helps but I just dropped my driveshaft off th be built yesterday. My TT is 50 15/16 long now. I cut exactly 21 inches out. My drive shaft from the center of he pinion pin hole to the center of the snap ring groove needs to be 45 3/4. Your mileage may vary.
     
  6. walter
    Joined: Nov 4, 2007
    Posts: 617

    walter
    Member

    My shaft sticks out one inck from the bottem of the bell. If lay a straight edge across the bell the shaft is inside the bell a quarter of an inch. I built my set up from an original matched tube and shaft. We cut the same amount from both. I hope that helps!
    Walter
     
  7. chiro
    Joined: Jun 23, 2008
    Posts: 868

    chiro
    ALLIANCE MEMBER

    ^^^Thanks Walter. That's exactly what I needed.

    Andy
     
  8. 31FordAV8
    Joined: Sep 26, 2011
    Posts: 3

    31FordAV8
    Member

    I Made Mine Out Of Three And Put A Straight Edge Across The Bell And The Tip Of The Driveshaft Is Even. That Was How The Original Model A One Was Also.
     
  9. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
    Member Emeritus

    A while back I looked over several Ford rears...I concluded the protrusion is not particularly precise as, within reason, it did not matter. It just hangs out within the U-joint and a fraction of an inch did not matter.
    Your point of precision is the stack of parts up front...bearings, sleeve seal, speedo gear, clip, etc.
    Assemble all of that, then dropitall into your tube and seat it. Where it stops with all parts assembled is right...
    Now figgerout the length at rear based on how far pinion stuff sticks out and shorten so it fits and the connector sleeve fits. Just ruler work back there.
     
  10. revkev6
    Joined: Jun 13, 2006
    Posts: 3,351

    revkev6
    Member
    from ma

    as always, bruce has the way to go. I replaced a torque tube/driveshaft on a buddies that broke during a rapid acceleration event. he had another torque tube that had been shortened so I just made another driveshaft the same length as the old one.... bad news it was a touch short!

    do it like bruce says. put the coupler on the pinion shaft with the pin. with torque tube gasket in place measure out from the face of the banjo where the torque tube mounts. the distance from this face to the center of the open rivet hole in the coupler is what you need.

    put the driveshaft in the torque tube with all the bearings spacers and snap rings. mark the back of the driveshaft where it sticks out of the back of the torque tube. take driveshaft out of the torque tube and measure forward from that mark the distance you measured on the coupler. This point will be where the hole for the rivet needs to go on the driveshaft.

    once the hole is in your length is simple!
     
  11. HotRodMicky
    Joined: Oct 14, 2001
    Posts: 1,764

    HotRodMicky
    Member

    Shaft is 1/8 inch shorter than the cup
     
  12. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
    Member Emeritus

    The controlling point is the thrust surface up front, where the bearings and speedo drive live. Set the shaft back against that and then jus measure rear of shaft against the prtrusion of the pinion gear and whatever coupler sleeve setup you are using. The bearings up front need to be happy and they do not care about protrusion up there...that varies slightly between individual rears and does not matter because the nose of the shaft does not come near to anything.
     

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