Welcome to Club Hot Rod!  The premier site for everything to do with Hot Rod, Customs, Low Riders, Rat Rods, and more. 

  •  » Members from all over the US and the world!
  •  » Help from all over the world for your questions
  •  » Build logs for you and all members
  •  » Blogs
  •  » Image Gallery
  •  » Many thousands of members and hundreds of thousands of posts! 

YES! I want to register an account for free right now!  p.s.: For registered members this ad will NOT show

 

Thread: Wrong yoke for my TH400? Counterbore?
          
   
   

Reply To Thread
Results 1 to 10 of 10
  1. #1
    hobo's Avatar
    hobo is offline CHR Member Visit my Photo Gallery
    Join Date
    Apr 2006
    Location
    Indiana
    Car Year, Make, Model: 1969 Nova SS, 2009 Street Glide, 1980 FL
    Posts
    70

    Wrong yoke for my TH400? Counterbore?

     



    Hey guys,

    After painstakingly measuring the driveshaft length for the Turbo 400 I'm putting in my nova, I finally concluded that I currently have 3/8" play and needed an additional 5/8" to get me to my 1" goal. I took it to the fab shop today to have it cut down and, luckily, the tech noticed that I didn't have as much of the yoke going into the tranny as I needed based upon my markings. This is my first 400, so I wasn't sure what to expect - but I'll bet that only 2/3 of the machined yoke surface actually fits into the tranny. Basically, he told me that my 600+ HP would twist the portion of the yoke that was in the tranny off, and that I needed to look for a "counterbore" yoke for my tranny.

    I'm going to the local race shop that I work with tomorrow to see what might be going on, but thought I would run it past the board beforehand. I did a search but didn't find anything that seemed to relate to this topic, so I apologize if I'm asking for something that's been answered elsewhere.

    Thanks...

    Hobo
    Don't ride/drive faster than your Guardian Angel can fly...

  2. #2
    pat mccarthy's Avatar
    pat mccarthy is offline CHR Member/Contributor Visit my Photo Gallery
    Join Date
    Apr 2005
    Location
    bay city
    Posts
    10,431

    the 1350 yokes do not have any counter bore spline up to the end of the yokes is this what you mean? the spline is what makes it strong not the counter bore if you have more then a 1 1/2 hookup on the spline you should be good

  3. #3
    brianrupnow's Avatar
    brianrupnow is offline CHR Member Visit my Photo Gallery
    Join Date
    Feb 2004
    Location
    Barrie-Ontario-Canada
    Car Year, Make, Model: 1931 Roadster Pickup
    Posts
    2,018

    When I built my roadster pickup driveshaft, I used a turbo 350 automatic tranny and rear yoke, to get the correct length of driveshaft. I slid the yoke into the tranny tailstock untill about an inch of it was still exposed, then built my driveshaft to suit. You can imagine my dismay, when a while later I was installing the driveshaft, which means that you must slide the yoke all the way into the tranny to let the rear universal move into place in the rear axle yoke---and the darned yoke wouldn't slide in that last inch!!! That one was a real head scratcher, untill Denny or Pat (I can't remember now which it was) on this forum come up with the suggestion that since it was a used front yoke, the internals splines might have gotten twisted during a "hard launch", which would prevent it from sliding in all the ways. So---I got out my trusty mag lite and looked up inside, and sure enough!!! About 1" from the bottom there was a definate "tweak" in the spline. I ran off to the auto parts store and bought a new front yoke, it slid all the way into place, and everything worked fine. I thought for about an hour that I had cut my driveshaft to the wrong length.---Brian
    Old guy hot rodder

  4. #4
    C9x's Avatar
    C9x
    C9x is offline CHR Member Visit my Photo Gallery
    Join Date
    Dec 2004
    Location
    N/W Arizona
    Car Year, Make, Model: Deuce Highboy roadster
    Posts
    1,175

    Probably not your problem, but one to be aware of.

    I have a dummy T-400 in my 31 on 32 rails roadster project.

    I couldn't get the yoke to slide on more than a half inch or so.

    Got a jack under the trans pan - with board to spread the load and floor stands - and removed the tailshaft housing.
    It's a short one on the big Buicks.

    Found the splines loaded with grit and dry mud etc.
    The trans probably sat out in the weather awhile before I got it.

    Wire brushing the splines clean allowed the yoke to slide on and bottom out.

    Next stop, driveshaft shop to cut 1" out of the shaft.
    C9

  5. #5
    hobo's Avatar
    hobo is offline CHR Member Visit my Photo Gallery
    Join Date
    Apr 2006
    Location
    Indiana
    Car Year, Make, Model: 1969 Nova SS, 2009 Street Glide, 1980 FL
    Posts
    70

    Pat - after I cut the driveshaft for 1" play, I would have about 1 to 1.5" of yoke actually hitting the splines of the tranny if the suspension were to bottom out...

    Brian - I did see that thread, but my yoke is a new Spicer unit that I just purchased. Regardless, I'll take a look.

    I'll still check with the race shop tomorrow. It seems like the yoke should be sliding in much further than it is, but I'm new to the auto-trans stuff - I guess I'm a hardcore "third pedal" guy at heart...
    Don't ride/drive faster than your Guardian Angel can fly...

  6. #6
    hobo's Avatar
    hobo is offline CHR Member Visit my Photo Gallery
    Join Date
    Apr 2006
    Location
    Indiana
    Car Year, Make, Model: 1969 Nova SS, 2009 Street Glide, 1980 FL
    Posts
    70

    Guys,

    I just spoke with Denny at Denny's Driveshafts, and I have to say that he was a TON of help. We're both betting that my TH400 is a threaded "truck" or "bolt-on yoke" style, which I will verify tonight. If that's the case, there is indeed a counterbore inside and a counterbored slip yoke is made to address the issue. All I need to do is verify my u-joint cap measurements tonight along with the driveshaft and order the correct yoke.

    Thanks everyone - I guess the learning never stops...

    Hobo
    Don't ride/drive faster than your Guardian Angel can fly...

  7. #7
    hobo's Avatar
    hobo is offline CHR Member Visit my Photo Gallery
    Join Date
    Apr 2006
    Location
    Indiana
    Car Year, Make, Model: 1969 Nova SS, 2009 Street Glide, 1980 FL
    Posts
    70

    Okay all - one more question. Before I purchase the $100 "counterbore" yoke, I decided to pull the tail off my tranny and see what was causing the yoke to stop it's travel. Turns out that the threaded shafts have a metal shoulder about 1/3" wide with an o-ring that is stopping the yoke from going the full length onto the shaft. I'm thinking about pulling out my p-grinder and smoothing out the metal shoulder, which would allow my yoke to slip in all the way and I likely wouldn't need to have my driveshaft shortened because of the extra slip it would give me. (It would also save me $100).

    Anyone know of a reason why I shouldn't do this, or problems it may cause? I wouldn't think that by smoothing this out all around the shaft I would cause any balance issues.

    Thanks...

    Hobo
    Don't ride/drive faster than your Guardian Angel can fly...

  8. #8
    robot's Avatar
    robot is offline CHR Member Visit my Photo Gallery
    Join Date
    Feb 2004
    Location
    Tucson
    Car Year, Make, Model: 39 Ford Deluxe Coupe
    Posts
    2,130

    Hobo, think about the torque that twists the splines on the yoke....now think about your grinder leaving nicks or stress risers in the shaft....what you would be trying to do is to make a lathe part using a hand held grinder!! What if you screw up and the shaft breaks? Is that a $100 error? What if the shaft breaks and the yoke goes sideways and takes out the transmission tailhousing/case? That may be at least $3 alone..... If you're asking, my advice is to pony up the $100 and do it right.

    mike in tucson

  9. #9
    bigdude's Avatar
    bigdude is offline CHR Member Visit my Photo Gallery
    Join Date
    Sep 2005
    Location
    Three rivers
    Car Year, Make, Model: 66 Nova SS 4 speed
    Posts
    372

    That spacer is a good thing-keeps your yoke from getting harmonics that could lead to vibration. Just spring for a different yoke summit has them also. I went through the same thing with mine-good luck.
    www.adoptafriendforlife.org

  10. #10
    hobo's Avatar
    hobo is offline CHR Member Visit my Photo Gallery
    Join Date
    Apr 2006
    Location
    Indiana
    Car Year, Make, Model: 1969 Nova SS, 2009 Street Glide, 1980 FL
    Posts
    70

    Okay guys - I'm convinced. That's why I'm a member of this board.

    Thanks everyone...
    Don't ride/drive faster than your Guardian Angel can fly...

Reply To Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
Links monetized by VigLink