I'm at a loss and grabbing at straws...

Discussion in 'Street/strip 400/430/455' started by Brett Slater, Jul 27, 2021.

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  1. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    I did it my self in my garage. Use jack stands, under the front lower control arms, and rear axle tubes. Buy one of those angle finder gauges. Measure the angle at the rear of the transmission. It should be pointed down. Then unbolt the rear u joint and push the drive shaft forward. Measure the rear pinion angle. The rear pinion moves UP under power, about 2*. Under power, you want the angles to cancel out to zero. If the rear of the transmission is down say 4*, you want the rear pinion to point up 2*. That way, under power, it points up 4*.

    http://www.buickperformanceclub.com/Pinion.htm
     
    Last edited: Jun 19, 2022
    LARRY70GS, Jun 19, 2022
    #141
    Brett Slater likes this.
  2. DaWildcat

    DaWildcat Platinum Level Contributor

    DaWildcat, Jun 19, 2022
    #142
  3. Brett Slater

    Brett Slater Super Moderator Staff Member

    Devon,

    That link is dead.
     
    Brett Slater, Jun 19, 2022
    #143
  4. DaWildcat

    DaWildcat Platinum Level Contributor

    DaWildcat, Jun 19, 2022
    #144
    Brett Slater likes this.
  5. Bigpig455

    Bigpig455 Fastest of the slow....

    Would you agree that the farther you push the axle downward in it's range of travel, the farther the pinion rotates downward? As shown in the pic in post 131, its riding higher in the rear than stock. Hey mine is the same way, and it looks good but its gonna change the pinion angle (from my understanding, I know when I measured mine was at the far end of spec) . I was able to tame mine with new bushings, good 50/50 shocks and airbags. However, I do agree he needs to measure and know where he's at first. I used a super cheap amazon gauge similar to the one in the link to understand my starting point first.

    https://www.amazon.com/Magnetic-Ang...9943&sprefix=pinion+angle+guage,aps,70&sr=8-8
     
    Bigpig455, Jun 19, 2022
    #145
  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Springs change the ride height by lifting the body higher. Moving the rear suspension up and down changes the distance between the transmission and rear axle. I'm not sure if that actually changes the pinion angle. Axle torque is what moves the pinion nose up under power. The No Hop bars change the instant center, and push the entire rear down under power.

    Looking at Brett's car pictures, it does not appear to me that his rear ride height is higher than stock. I don't think his pinion angle is the culprit here. I'd be measuring it first before changing anything.
     
    Last edited: Jun 20, 2022
    LARRY70GS, Jun 20, 2022
    #146
    Brett Slater likes this.
  7. Brett Slater

    Brett Slater Super Moderator Staff Member

    Current stance:

    20220608_191058.jpg
     
    Brett Slater, Jun 20, 2022
    #147
  8. rkammer

    rkammer Gold Level Contributor

    Is this the adjustable upper control arm being discussed? I never realized my GS has them until I got under the car with the muffler guy while installing my Walker Super Turbos. Don't know if they are adjusted right or not but, the car doesn't wheel hop on takeoff.
    IMG_8286.JPG IMG_8287.JPG
     
    rkammer, Jun 20, 2022
    #148
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  9. Brett Slater

    Brett Slater Super Moderator Staff Member

    That's what they look like, yes.

    If you're not experiencing any type of wheelhop, I'd say they're adjusted correctly.
     
    Brett Slater, Jun 20, 2022
    #149
  10. 12lives

    12lives Control the controllable, let the rest go

    But have you greased them in the last 10 years??? ;)
     
    12lives, Jun 20, 2022
    #150
    1973gs likes this.
  11. rkammer

    rkammer Gold Level Contributor

    :) Only owned the car for about 2 1/2 years. But, I'll check them, thanks for the heads up.
     
    rkammer, Jun 20, 2022
    #151
    Brett Slater likes this.
  12. Schurkey

    Schurkey Silver Level contributor

    Pinion angle changes with ride-height; or with suspension movement in general.

    There are long arms on the bottom of the axle, short arms on top. What else is like that? The front suspension has a long arm on the bottom, and a short arm on top. Front suspension camber changes with suspension movement. Same deal--turned sideways--at the rear axle.

    Yes. Keep in mind the OEM control arms are deliberately flimsy in torsion, to prevent suspension binding. Aftermarket control arms tend to be stiffer in torsion; absolutely not wanted but they can be advertised as "stronger" to folks who don't think it through.

    Wisdom.

    Virtually guaranteed to be high in back. At normal ride height, the fender would cover more of the tire, and the rocker panel wouldn't tilt up at the rear. This is why I suggested that you verify the ride-height USING THE GM PROCEDURE which is to measure from the top of the axle housing to the frame.
     
    Schurkey, Jun 20, 2022
    #152
  13. CJay

    CJay Supercar owner Staff Member

    I doubt after 50 years any of these cars sit at the factory ride height.

    20220620_172419.jpg
     
    CJay, Jun 20, 2022
    #153
    FLGS400 and Brett Slater like this.
  14. CJay

    CJay Supercar owner Staff Member

    Fir some reason it's brighter without the stupid flash...

    20220620_172550.jpg

    I just measured my car. It's listing to the drivers side by 1/2".

    If you notice, GS's ride lower than skylarks
     
    CJay, Jun 20, 2022
    #154
    Brett Slater likes this.
  15. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Here's a scan,

    TrimHeightChartB.jpg
     
    LARRY70GS, Jun 20, 2022
    #155
    patwhac, alvareracing and Brett Slater like this.
  16. Schurkey

    Schurkey Silver Level contributor

    OK, I'm surprised.

    When measuring from the ground to the fender lip, rotted body bushings will make the body sit low. I didn't expect Buick to produce measurements that way.

    My '68 Chevelle/El Camino service manual avoids that by listing the dimension between axle tube and frame rail. There's a small allowable variance, and the dimension changes a little depending on how the car is optioned.
     
    Schurkey, Jun 20, 2022
    #156
  17. 12lives

    12lives Control the controllable, let the rest go

    They never expected the cars to last long enough to have rotten body bushings! :(
     
    12lives, Jun 21, 2022
    #157
    Oldskewl59, chrisg, hwprouty and 1 other person like this.
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