1. Welcome to PlowSite. Notice a fresh look and new features? It’s now easier to share photos and videos, find popular topics fast, and enjoy expanded user profiles. If you have any questions, click HELP at the top or bottom of any page, or send an email to help@plowsite.com. We welcome your feedback.

    Dismiss Notice

1/2 ton to 3/4 rear axle conversion q's

Discussion in 'Chevy Trucks' started by Garet, May 22, 2001.

  1. Garet

    Garet Senior Member
    Messages: 106

    I just got a 14 bolt axle for free from an uncle. Problem is the yoke on the 14 is bigger than the 12 so the u-joint doesn't want to bolt up. The driveline off the 3/4 ton is a two piece one and it is from a 2wd so it's not going to work. The one on my 1/2 ton is 1 piece and is heavy duty so I want to keep it. Now, should I change the yoke on the axle, or the yoke on the driveshaft, or should I just get a whole different driveshaft? I heard that you can get the yokes changed on the driveshaft, but what I don't know is if you can get them changed on the axle. Also is the end which splines in the same size on all drivelines from 73 to 74? I mean the end without a u-joint you can just pull off.

    thx

    garet
     
  2. 75

    75 PlowSite.com Addict
    Messages: 1,382

    Garet: I don't know about the spline question, but I would definitely not get into changing the yoke on the axle. Have the driveshaft modified to suit - mixing parts this way often leads to a bit of "custom-fab" work.
     
  3. Chuck Smith

    Chuck Smith 2000 Club Member
    from NJ
    Messages: 2,317

    If the driveshaft from your truck, is the proper length, possibly you can find a U joint to make it work. You can get u joints with 2 different size bearing caps on them. Then again, you could also get your driveshaft modified for about $150, if the length is OK.

    ~Chuck
     
  4. Mudbug44s

    Mudbug44s Junior Member
    Messages: 11

    Garet,


    Hey just a quick note. I have 8" of suspension lift on my shortbox. When I lifted it that high my rear D-shaft was a little too short. By switching to a 14 bolt axle which is a LOT larger and has a longer Pinion snout I gained back a few inches that I needed.

    I used a conversion U-Joint (Like Chuck said) and kept my half ton driveshaft. The Joint was a NAPA part and when I get a chance I will go look in my tool box for the Part #. It was for a half ton FORD, '77 I think. The U-Joint has a larger cross and bearing caps on one side and the other fits into the stock driveshaft. The Joint is kind of expensive, (About $30) but it got me by untill I could get new larger shafts made up. Good luck,

    Andy
     
  5. Garet

    Garet Senior Member
    Messages: 106

    Driveshaft

    Thx Andy. I would appreciate you looking that up. I am concerned about the length. I am going 6" so it should be long enough with the extended 14-bolt bolt distance over the 12 bolt. By the way, if I do go with a special u-joint is it going to be strong enough to power the 14 bolt with 36's? The differnce n size isn't all that much but a little probably makes a big difference. My 350 doesn't have the torque the 454 has so it probably doesn't need a bigger u-joint. Which puts more stress on u-joints anyway, engine torque or tire size?

    garet
     
  6. Power mad

    Power mad Member
    from Oregon
    Messages: 75

    Hey all
    There are 2 u-joints depending on what yoke is on it.
    Napa # 348 or 447.
    I think one is for a 1 1/16 cap and the other is 1 3/16 inch cap.
    See ya
     
  7. Chuck Smith

    Chuck Smith 2000 Club Member
    from NJ
    Messages: 2,317

    Actually, 3 things are involved in you question Garet. The engine puts out X amount of torque. That is transferring through the ring and pinion. Depending upon the axle ratio, the amount of torque needed to turn the tires can vary, in a sense. The lower the gear ratio, the easier it is for the tires to turn, which = less resistance, which = less torque on the yolk. I have seen trucks (not pick ups) twist driveshafts into pretzels, due to high torque, and a heavy load on them. Amazingly, the u joints didn't blow, but there was enough torque to twist the driveshafts.

    So in a nutshell, the bigger the tire, the more resistance, the more stress put on the U joints, and yolks. Match your gear ratio to your tire size, and that reduces the resistance.


    Hope I didn't confuse you. Not sure what size tires you plan to run, but a set of 4.11 gears, and 36" tires is a good combination.

    ~Chuck
     
  8. Garet

    Garet Senior Member
    Messages: 106

    tires

    I am going to be putting on 36's so that is a plus if they work well with 4.10 gearing. I now just need a th400, dana 60, and a good transfer case....:)
     
  9. Power mad

    Power mad Member
    from Oregon
    Messages: 75

    Chuck
    Thanx for the insight.
    I have a 78 K5 355 plant and 465/205 drive train.
    I also have a 73 C20 pick up with a .040 over 454.
    I am going to swap the 14 bolt and 454 into the Blazer.
    The 14 has a 3:73 same as the 12 bolt in it now.
    I have 33's on it same as the 73, but I will be going to 36's on the next set.
    After reading your post I realized that allthough I would be able to twist 36" tires with a BBC and a 3:73 ratio I would be winding the shaft like a pretzle.
    I have a shaft from a 72 riviera(sp) that has a double cardon on it the same size as the one in the front. The Riv had a 455 in it and this is one beefy piece of pipe.
    Now I just need to make another front shaft that will take the abuse of a BBC and 3:73 gears.
    Which would be cheaper than a set of gears.
    I have a buddy that has a full on machine shop at his house.
    He's 58 and the neatest guy you ever met. You can make anything at Jims house. He's even got 2 engine boring machines that he hardly ever uses(10 years) Can you say 468 cubic inches YEAH
    See ya
     
  10. Chuck Smith

    Chuck Smith 2000 Club Member
    from NJ
    Messages: 2,317