Ride height question

Discussion in 'Chassis restoration' started by Houndogforever, Mar 8, 2022.

  1. Houndogforever

    Houndogforever Silver Level contributor

    I look at the service manual and it gives the following diagram for the skylark.
    frame.jpg

    So, the datum plane. Is that a surface to use while setting this up? It says the T dimension is 5" below the frame.
    So, is that an imaginary line or is it the ground when sitting there? I mean, is there just 5" between bottom of frame and the ground? That can't be right because as it sits now, there is 10" between bottom of center frame to the ground.

    Anyway, is there any information where that datum line is physically? Or should I just load up the car as if it were fully assembled and make is level?

    What is the distance between the frame bottom on your cars?
    Thanks for the help.
     
  2. 12lives

    12lives Control the controllable, let the rest go

    Imaginary - "an assumed surface used as a reference for the measurement of heights and depths." So if you set a frame on a frame table/rack (perfectly flat surface) you should get those dimensions at the indicated points.
     
    Last edited: Mar 9, 2022
  3. Houndogforever

    Houndogforever Silver Level contributor

    Well then. I guess I just load it up in weight and make sure the bottom of the frame is level front to back.
     
  4. 12lives

    12lives Control the controllable, let the rest go

    I'm not sure what your concern is. The car is going to sit however you want it to. You can control it by springs, tire/wheel size, spacers, etc. The factory specs are to see if a frame is tweaked. What are you trying to accomplish?
     
  5. LARRY70GS

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

    Check Section 30 in the 1967 Chassis Manual.

    Figure 30-5, Figure 30-18, and paragraph 37-2 on page 30-14
     
  6. dynaflow

    dynaflow shiftless...

    ...or, for ride height look in Assembly Manual for page with "trim height dimensions." Don't know about other years, but for my '71 it's page 0-6.1. "Curb height" about 10" to bottom of rocker at ft fender/door gap, give-or-take depending on model/engine. No exaggeration to say I use that book almost every day...
     
  7. Houndogforever

    Houndogforever Silver Level contributor

    What I'm trying to do is get the car sitting at it's approximate ride height. Once established there, I can tighten all the suspension bolts that are finger tight.
    Also then I need to measure my pinion angle on the diff and using my adjustable upper control arms, set that to correspond to the transmission angle.

    Everything I read says to only torque down the suspension bolts when at ride height, otherwise it puts a twist in the rubber bushings.
     
  8. sean Buick 76

    sean Buick 76 Buick Nut

    Put the appropriate amount of weight back on the car and then tighten the bolts.
     
  9. Houndogforever

    Houndogforever Silver Level contributor

    Well yeah, lol. That's the whole point. What is "the appropriate amount of weight" I can add a quick 230lbs by stuffing my son in the trunk.

    I starting to think that if I'm within an inch of final height, the twist in the rubber probably can't be an issue. Particularly since it will never be a daily driver. So long as it's level while standing free.
    I'm probably over-thinking shiz again.
     
  10. LARRY70GS

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

    Why don't you just wait until the car is at curb weight with everything installed, spare tire, and full tank of gas, and then tighten the control arm bolts?
     
  11. Houndogforever

    Houndogforever Silver Level contributor

    Because I don't have a drive line and would like the car to be self mobile. Can't get a driveline until I set pinion angle, can't set pinion angle until car is at ride height. I was just hoping I could crank a ratchet strap around a cross member front and rear and pull down until I got to a number. Then make sure it's level and I'm off.
     
  12. LARRY70GS

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

    That's doing things backwards.
     
  13. Houndogforever

    Houndogforever Silver Level contributor

    I never said I'm a smart man.
     
  14. LARRY70GS

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

    :DI never said you weren't.
     
  15. 12lives

    12lives Control the controllable, let the rest go

    OK, that explains it. I agree with Larry - setting the suspension and tightening the bushing bolts is the almost the last thing to do. Wait until the car is "finished" with all the weight in. I have even heard of people putting a weight in the drivers seat before tightening the bolts. I may be wrong and someone correct me - but I do not believe changing the pinion angle is going to strain the bushings. Thats why I said every car is unique. For example - you are putting a non-stock engine in - that changes your car from the manual specs.
     
    Last edited: Mar 10, 2022
  16. 12lives

    12lives Control the controllable, let the rest go

    You say you want the car to be mobile - it wont hurt to move the car with the bolts slightly loose, or even to drive it a little bit slowly. You can always loosen them and re-tighten them any time later.
     
  17. Houndogforever

    Houndogforever Silver Level contributor

    If I measure for the drive shaft now as it sits, and then it settles another inch at finish ride height, Is that any problem?

    I know when you stomp on it, the diff will roll back, hense pulling the yoke out of the transmission a little.
    How much is a little?

    Is there any forces that will cause the diff to roll forward pushing the yoke into the transmission causing damage?

    I believe I have read that you push the yoke in and back it out 3/4"-1" and then measure. Can I do that at the current settings just so I can get a driveshaft made?
    I'm fine with leaving all those suspension bolts loose for now, I have big red ribbons attached to all the loose points to remind me.
     
  18. 12lives

    12lives Control the controllable, let the rest go

    Great questions - I would think best answered by whoever is going to make your driveshaft. The drive line experts have good info!

    I like the red ribbons!
     
  19. sean Buick 76

    sean Buick 76 Buick Nut

    No you need all the weight on the chassis before you can have a driveshaft made properly.
     
  20. 12lives

    12lives Control the controllable, let the rest go

    Thanks Sean! So you could use a 4 post lift but not a 2 post that lets the suspension hang down? Can you recommend a website for the procedure? I'll be doing this as well.
     

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