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Driveline Angle

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by JungleBoy, Aug 28, 2001.

  1. JungleBoy

    JungleBoy 1/2 ton status

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    Installing the NV4500 in place of the M465, and the assembly is quite a bit longer than stock 71 Jimmy 4x4). I measured a driveline angle of about 15 degrees with stock suspension and am planning an a slight lift to get some positive spring arch up front. What is an acceptable limit for driveline angle? How is the best way to adjust the angle? I will be installing a 14bolt FF, and am thinking that rotating the spring pads would work OK. Thoughts?
    Thanks as always
    JB
     
  2. JST12

    JST12 1/2 ton status

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    I have read from driveline experts that you can go up to 15 degrees of angle on your u-joints. They say it is the absolute limit. I am running about 13-14 degrees and my diff and xfer case are within 1 degree of parallel with each other. I do not have any vibration that I can tell so far. I do think that the u-joints will wear out sooner with more angle since the bearing caps are rotating back and forth a lot more with each revolution of the driveshaft. JT

    PS... Do remember that you need the same u-joint angle on both ends of the driveshaft to eliminate vibration. You could tilt your diff up using shims or rewelding your perches, but if the xfer case end is not tilted down or a CV joint is not used instead, you will add vibration.

    <P ID="edit"><FONT class="small">Edited by JST12 on 08/28/01 09:54 PM.</FONT></P>
     
  3. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    I'm pretty sure I have a 20 degree driveshaft angle. With 8" rear springs, 6" front.
    I have a 1350 CV joint off the Transfer Case, which has two ujoints and basically takes the driveshaft angle and divides it in two. Good investment.

    As for the pinion angle, One Friday afternoon I took my 12 bolt rearend to a mechanic shop who was very confident he could do the job...Larry Freeman of Freeman Frame in San Jose, I had the spring perches at 14 degrees when I brought the rearend to him.
    I brought some heavy duty spring perches that would give 1/4" more lift. I handed them to him, and what does he do but misplace them, by setting them down somewhere, and we spend a half an hour looking for them. I finally found he set them down in an engine compartment of some car in his shop.
    ...So I showed him the shim that I took out of the bottom of the leaf spring pack. I wanted to eliminate this 4 degree wedge, so I told him to put the new spring perches at 18 degrees. It was at 14 + 4 degree wedge getting rid of = 18 degrees. He even had the magnetic tool to measure the angle. I double or triple checked the measurements with the guy so there was no confusion as to what I wanted.
    I put the rearend pinion angle at 18* which is 2* under the 20* driveshaft angle. I belive you want it 2* less, because the rearend shifts up slightly under acceleration.
    I picked up the rearend, he overcharged me by $30 then what we agreed on. I came back in 1 1/2 hours and it was done, not 2 hours. Brought the rearend home, bolted it up, looked at it, and the dude welded it at 2 degrees.
    ...Yes, completly opposite direction and off by 16 degrees.
    I took some poloriod pictures, called his ass up and told him I'd be back on monday.
    Saturday I borrowed my neighbors cutting torch and got rid of the springs, called around found another set of spring perches, and my buddy came over with his MIG welder and we bolted the rearend up to the springs, tightened up the u bolts loosly and tack welded the spring perches when we got the rearend lined up with the driveshaft perfectly. Then we lowed the rearend back down and finished welding the perches.
    Monday I went back and argued with the guy, showed him the poloroid pictures, and told him I wanted all my money back.
    He said he'd split fault of the mistake with me and give me half of my money back, he handed me some money and when I counted it, it was 3/4 of what I originally paid him, so I left.

    My advise is that it is not that hard to do that kind of stuff yourself if you have the tools and the motivation. My gut instinct was that I should have done it myself all along rather than trust any shop to do it.
     
  4. JST12

    JST12 1/2 ton status

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    I had the same thing happen. I went to a local welding shop to have my perches cut and rewelded. I don't know how many times I went over the procedure with the owner to get the angle right. When I installed the axle, it had zero degrees! Turns out the owner never told the actual guy who was going to weld the axle what we had discussed other than set the perches at 40 inches center to center.

    Anyway, you can indeed have any driveshaft angle you want if you are using a CV joint. 15 degrees is the max if you have u-joints at both ends. And it is not 15 degrees relative to the ground, it is 15 degrees of bend relative to the xfer case housing and 15 degrees relative to the pinion flange.
    JT
     
  5. JungleBoy

    JungleBoy 1/2 ton status

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    Thanks for the info. I guess the CV joint is the thing to do. The front driveshaft has a Spicer CV joint - where can I get another (or two) "new" and how much should I pay?
    JB
     
  6. Steve_Chin

    Steve_Chin 1/2 ton status

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    Larry, I got a complete new front driveshaft for my Blazer when I was going to have a driveline shop rebuild it. Seems that the labor involved in taking apart the thing is more expensive than the parts to make up a new one.
     

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