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Thread: 3-Link Owners: You Guys Have Driveshaft Bind at Full Droop?

  1. #1
    Member Jim Doak's Avatar
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    3-Link Owners: You Guys Have Driveshaft Bind at Full Droop?

    I just finished installing a 3-link retrofit on my old Mark 1. Like with my 4-link, the 3-link has driveshaft bind when the rear axle is at full droop. (I've been running an axle limiting strap from my differential to the 3x2 crossmember above the axle with the 4-link.)

    I called Factory Five yesterday and the gentleman I spoke to said that the limiting straps are not used to prevent driveshaft bind; instead, they're a safety device to prevent overextension of the shocks/springs for builders using the donor Mustang shock and spring setup. He also said that limiting straps are not needed for cars running Konis. (I'm running Konis on my car.)

    I've made rough adjustments to my pinion angle following the 3-link install but still get driveshaft bind at full droop. (Approximately 2* down as compared to the engine/transmission angle.)

    So, I have a few questions for you guys:

    1. For owners without limiting straps: Do you have driveshaft bind at full droop?

    2. Are you running limiting straps with your 3-link install?

    3. If you're not running limiting straps and have driveshaft bind at full droop, has that ever been a problem under normal driving conditions?

    Thanks.

  2. #2
    Senior Member rich grsc's Avatar
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    I just have one question, how are you going to drive around with the rear suspension unloaded?

  3. #3
    Member Jim Doak's Avatar
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    I'm not; I'm wondering what would happen if the car becomes unweighted at speed going over a rise/bump.

  4. #4

    Steve >> aka: GoDadGo
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    I'd reach out to one of the Master Builders like:

    Mike Everson, Gordon Levy, Jeff Kleiner, Mark Dougherty and Wayne Presley.

    All of these fellows have done many, many builds so I bet they'd know for sure.

    Several of these folks have helped me with my issues so I know they'll help you.

    Good Luck!

  5. #5
    Senior Member CraigS's Avatar
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    When I had a 3 link I ran a strap like you near the center of the car. Way back when, they used to run 2 straps to the bottom of each shock. Then we realized that would restrict the body roll and/or pick up the inside tire in a hard turn. The central strap keeps the drive shaft good w/o the other problem. Another question for you though. How is the drive shaft w/ the axle all the way up? You need to remove the springs to test that. I ask because you may need to lower the trans some if you have any spacers under the mount.
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

  6. #6
    Mark Dougherty's Avatar
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    yes
    normally the front of the drive shaft does bind when the rear suspension is at full droop.
    this is no issue as most do not drive the car like this.
    If you find that you are going to be driving in such a way that you would be fully unloading the rear suspension
    IE: jumping railroad tracks then you can run more pinion up to eliminate the issue.

    Now this will begin a whole new ( or old thread ) about matching pinion angles.

    And Craig has a good point about the opposite issue but I have only run into this when using an old automatic drive shaft.
    they had a harmonic balancer attached to the slip yolk which limited universal travel further than other style shafts.
    Last edited by Mark Dougherty; 09-26-2017 at 12:35 PM.
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  7. #7
    Not a waxer Jeff Kleiner's Avatar
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    Yes, the joints bind at full droop. If you get to full droop while driving you're gonna' have bigger problems than universal joints though!

    Jeff

  8. #8
    Member Jim Doak's Avatar
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    Thanks for the input, guys. It sounds like I should be good to go without the limiting straps.

  9. #9
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    I have a 3 link and i also have limiting straps. Actually the straps are chains inside a bicycle innertube so that there is no rattle. Hopefully I will never need the straps, and they just there as insurance if they are ever needed.

    I really did like it when Bo and Luke did their Yee-Hah, but the landing was probably not that great.

  10. #10
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    No limiting straps, no binding.

  11. #11
    Senior Member Avalanche325's Avatar
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    BMW.jpg

    Have you been doing this?

    One of my favorite car pictures.

  12. #12
    Boydster's Avatar
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    Quote Originally Posted by Avalanche325 View Post
    BMW.jpg

    Have you been doing this?

    One of my favorite car pictures.
    Years ago, I gave my brother this pic as a poster when he started playing with Beemers. Also one of my favorites.
    ---Boyd---
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    427W, TKO600, Moser 3.55 rear.
    Delivered Feb 2017, Graduated Nov 4, 2019

  13. #13

    Steve >> aka: GoDadGo
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    Quote Originally Posted by Avalanche325 View Post
    BMW.jpg

    Have you been doing this?

    One of my favorite car pictures.
    Flying A Factory Five Looks Like A Lot Of Fun!

    Great Idea So Thanks For Sharing!

    All kidding, this is a great pic.

  14. #14
    Senior Member AC Bill's Avatar
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    Quote Originally Posted by Jeff Kleiner View Post
    Yes, the joints bind at full droop. If you get to full droop while driving you're gonna' have bigger problems than universal joints though! Jeff
    I was thinking the same thing, on the aspect of running two limiting straps, that body roll might lift an inside wheel on hard cornering. If it's gotten to that point, you'd probably not going to make the corner anyway..

  15. #15
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    prior to adding springs to the rear Bilstien shocks, I used a jack to move the axle up to top of travel and lower to full shock extension. I added shims at the rear of the trans so that I had no bind except that at full extension I had just a spot on the u-joint that hit lightly. I ground a little clearance. On my current shocks I added a limit strap just short of full shock extension on each side to protect the shock.

    You could take the springs off, leave the shock on, and move the axle to full up travel. Adjust trans tail height to just short of driveshaft limit. then check to see if you have bind at full droop. Add limit strap to prevent it if you do. I drilled a new hole for the strap so as not to limit my travel any more than necessary.

  16. #16
    Member Jim Doak's Avatar
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    Thanks for the input, guys.

    I took my car for a test drive yesterday. Everything seems to be OK except for one observation. On my test drive I drove up to the Snowbird ski resort which is about 11 miles uphill from my house. No strange noises on that half of the trip. However, on the way down the mountain I did notice some very minor noise/vibration.

    I think that what's happening is that I don't have enough "up" pinion angle on my differential and that when it's unloaded it's causing the vibration. Because I didn't have any vibration/noise when the differential was loaded and I was heading uphill.

    I'm going to try and replicate loaded ride height on my scissor lift and measure pinion angle and transmission/engine angle and adjust as necessary.

  17. #17

    Steve >> aka: GoDadGo
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    Quote Originally Posted by Jim Doak View Post
    Thanks for the input, guys.

    I took my car for a test drive yesterday. Everything seems to be OK except for one observation. On my test drive I drove up to the Snowbird ski resort which is about 11 miles uphill from my house. No strange noises on that half of the trip. However, on the way down the mountain I did notice some very minor noise/vibration.

    I think that what's happening is that I don't have enough "up" pinion angle on my differential and that when it's unloaded it's causing the vibration. Because I didn't have any vibration/noise when the differential was loaded and I was heading uphill.

    I'm going to try and replicate loaded ride height on my scissor lift and measure pinion angle and transmission/engine angle and adjust as necessary.

    Check your pinion angle & drive shaft output angles to make sure they are in phase at ride height or bad things will happen.


    You want the axle to be set between 1 & 2 degrees downward for a proper pre-load so the pinion flange should be tipping down just a tad when compared to the output shaft of your transmission. Also, check your yoke depth to make sure that you've got enough and not to much of the yoke riding inside the tail shaft of your tranny.

    U-Joint Phasing Video:


    https://youtu.be/Idk3BVDVHq4

    The upper link really needs to be locked down tight so check that too because it can work it's way loose. A crow foot wrench works well as does a very small plumbers wrench if you don't have the other tool.

    Good Luck!
    Last edited by GoDadGo; 09-29-2017 at 12:59 PM.

  18. #18
    Member Jim Doak's Avatar
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    I simulated ride height as best I could (a four post lift would be handy) and found that my engine/transmission was about 2.5* down while my pinion/differential was about 0.5* down. So I adjusted my pinion angle to about 1.5* up and took the car for a drive.

    So far, so good...no vibrations and at full droop I no longer have any driveshaft bind. So I was able to pitch the axle limiting chain I built using Derald Rice's method.

    I've read the guidance and according to it my pinion angle should be at about 0.5* up instead of the 1.5* up angle I'm using. The reason for the difference is that I'm using Mark Reynolds's heim jointed lower control arms. So I don't have any rubber bushings in my rear suspension.

    Thanks for the help.

  19. #19

    Steve >> aka: GoDadGo
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    Hope the U-Joint Phasing Video helped you as much as it helped me.

  20. #20
    Mark Dougherty's Avatar
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    good news
    I am glad you figured it out.
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