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    Results 21 to 31 of 31
    1. #21
      Join Date
      Feb 2016
      Location
      Texas
      Posts
      93
      Country Flag: United States
      A few more things to check out:

      (1) I got a new DS from PST a while back and had to have it rebuilt. Check yours out, get the balance checked. My "new" DS arrived with a junk no name, no number (Chinese?) yoke that did not hold the u-joint cups tightly, they were so sloppy the DS shop could not even check the balance so I had to have it replaced.

      (2) Make sure you have not torqued the u-joint u-bolts too tightly or they may bind. Torque should be 17 lb-in (not lb-ft). Compress the lock washers flat plus 1/8th turn is a good approximation.

      (3) Does the slip joint fit far enough into the trans tail shaft? If not, it may wobble causing a vibration.

      (4) Calculate the critical speed for your DS. As mentioned above, your 4.10 really spins the DS, but I doubt 75mph will exceed the critical speed at which point the DS will wobble and could fail. The problem is worse for longer DS's. I suspect that PST checks the critical speed and would not make a DS where the critical speed would be exceeded.

      (5) The tracking offset you mention above probably doesn't help, but you can check the angles.

    2. #22
      Join Date
      Sep 2016
      Location
      Winnipeg, Manitoba, Canada
      Posts
      21
      Country Flag: Canada
      I have been fighting the exact same problem as you. At 70mph and up a pulsing vibration. Driveline angles were not great. I have a Ford racing 306 with TCP motor mounts, Tremec TKO600 with American Powertrain tranny brace, American Powertrain's steel driveshaft, and a Strange 9 inch with 4:11 gears in a 65 Mustang. I have had the engine lowered by one inch by recutting the motor mounts from plate stock (to decrease the tranny angle to 3 degrees down), had the diff shimmed up so that the tranny and diff are now the same angles (but opposite) and the driveshaft working angles are good. Still there, also had tires rebalanced, made sure rims are centered on hub (rims are not hubcentric), had driveshaft balance 3 times (once they rewelded the yoke because they said it wasn't quite right), also replaced U-joints....guess what, still there. I have brought the car to a local hot rod shop who have a lot of experience with fabrication and they said they have seen this a few times and recommend getting a High speed balanced shaft (nobody in my city does high speed balancing) so we have ordered a chromoly shaft and it will be installed and tested this week. I will let you know what the result is, keeping my fingers crossed as I have been chasing this for about 5 years so far with no success. The next option if this doesn't work is maybe to investigate a CV driveshaft from the Driveshaft Shop.

    3. #23
      Join Date
      Sep 2016
      Location
      Winnipeg, Manitoba, Canada
      Posts
      21
      Country Flag: Canada
      I noticed you are also on my post about the Strange diff leaking. Have you been happy with your Strange diff? I have been happy with the diff as far as performance but not with service and the leaking issue, now I see you have trouble with the U-joint install. Just wondering how prevalent these issues are with Strange products.

    4. #24
      Join Date
      Sep 2016
      Location
      Winnipeg, Manitoba, Canada
      Posts
      21
      Country Flag: Canada
      No, not totally happy. They did nothing to help out with the initial leak. Was told by diff shop that the housing was a little out of true but we got it to seal anyway. That being said the diff has worked fine (other than the leak) and the vibration I have been chasing seems to be driveline angle related. So I would say they have a reputation for good product and the diff shop said the center section was a very nice piece.

    5. #25
      Join Date
      Sep 2016
      Location
      Winnipeg, Manitoba, Canada
      Posts
      21
      Country Flag: Canada
      Installed the chromoly shaft...no change. Ran it without the axles on the lift and vibration still there. Still a driveline angle issue, looking into raising the rear of the car to decrease the transmission angle closer to 3 degrees. The Driveshaft Shop wants to know the angles (we are still playing with the shims and shackles to get better angles) before recommending the CV driveshaft. The shop put in a 3:50 rear end to check the carrier and it moved the vibration up to around 100mph so we know it is driveline angle related. Now working on getting the angles better. I never realized it would be so sensitive to such small variations but running 4:11 gears really has magnified the problem. Will keep posting until it gets resolved, I only hope I don't go broke trying to fix it.

    6. #26
      Join Date
      Sep 2016
      Location
      Winnipeg, Manitoba, Canada
      Posts
      21
      Country Flag: Canada
      Okay, Driveshaft Shop says my driveline angles are good so no CV driveshaft. The 3:50 gears make the car hook up better than the gonzo 4:11 gears (which are a lot of fun) but the vibration is still there. We put longer shackles on the car to get the rear up a bit (looks fine) and decrease the tranny angle. Shop put diff back to 1 degree but I think it needs to go up a degree as I was getting rumbling on the deceleration. So I am running out of budget to fix this issue and have gotten nowhere. Not sure what to do, guess it will be a city car only....

    7. #27
      Join Date
      Feb 2016
      Location
      Texas
      Posts
      93
      Country Flag: United States
      So what are all the angles now?

    8. #28
      Join Date
      Apr 2001
      Location
      The City of Fountains
      Posts
      15,971
      Country Flag: United States
      Quote Originally Posted by Dinorider View Post
      ...Shop put diff back to 1 degree ...
      This means nothing...

      Andrew
      1970 GTO Version 3.0
      1967 Cougar build
      GM High-Tech Performance feature
      My YouTube Channel Please Subscribe!
      Instagram @projectgattago
      Dr. EFI
      I deliver what EFI promises.
      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    9. #29
      Join Date
      Sep 2016
      Location
      Winnipeg, Manitoba, Canada
      Posts
      21
      Country Flag: Canada
      These are the angles now 2.8 down at tranny, 2.5 at diff, 1.6 down on driveshaft so angles good. Now looking at pinion yoke...? slightly off center. If this checks out not sure what to do next.

    10. #30
      Join Date
      Apr 2001
      Location
      The City of Fountains
      Posts
      15,971
      Country Flag: United States
      Quote Originally Posted by Dinorider View Post
      These are the angles now 2.8 down at tranny, 2.5 at diff, 1.6 down on driveshaft so angles good. Now looking at pinion yoke...? slightly off center. If this checks out not sure what to do next.
      If the rear of the trans is down 2.8 and the driveshaft is down 1.6 that makes your front operating angle 4.4 degrees. The front angle forms a shallow V.

      If the pinion is down 2.5 and given the driveshaft angle, the rear operating angle is 4.1. The rear also forms a shallow V.

      Given those numbers, I say your angles are similar, but they are not in opposite directions, as they should be. In other words, it looks like this:

      \ ___ /

      What's worse, is that under power, both the front operating angle gets bigger as the pinion rises.

      Andrew
      1970 GTO Version 3.0
      1967 Cougar build
      GM High-Tech Performance feature
      My YouTube Channel Please Subscribe!
      Instagram @projectgattago
      Dr. EFI
      I deliver what EFI promises.
      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    11. #31
      Join Date
      Dec 2010
      Location
      Fredericksburg, VA.
      Posts
      3,155
      Country Flag: United States
      Actually, based on the above numbers the front u-joint working angle would be 1.2deg because both trans and ds are angling down front to rear you would subtract the drive shaft angle from the transmission angle. If the ds was level or zero the front working angle would be 2.8. If the ds was angled up front to rear then you would add the angles together. With the ds running down front to rear and the rear end pinion running up front to rear, the rear working angle would be 4.1 which is a bit strong. Raising the rear end pinion yoke up 1 degree would also raise the rear of the ds increasing the front working angle and making both the front and rear working angles very close depending on the length of the ds. The goal is to get both front and rear working angles as close to each other as possible while staying under 3 deg.



      The other dimension that most people do not take into consideration is the drive line angles looking down from above. If the ds is offset to one side or the other front to rear that can also add to the overall working angles of the drive shaft.
      Steve Hayes
      "Dust Off"
      68 Camaro

      Given sufficient initial acceleration, even pigs can fly!


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