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Hot Rods Pinion Angle Bare Frame??

Discussion in 'The Hokey Ass Message Board' started by thegearhead, Sep 5, 2019.

  1. thegearhead
    Joined: Nov 23, 2015
    Posts: 35


    So i'm starting to put my car back together and i want to set the pinion angle. I know the vehicle is supposed to be complete and sitting level with all the weight on it. Issue i'm having is it's not complete yet and i need to also shorten my driveshaft so i know how wide/high i got to build the floor tunnel.

    Is there a way of setting the pinion angle this way or? Also i don't know the original ride height as i upgraded the suspension from factory. Thanks

    Attached Files:

  2. KevKo
    Joined: Jun 25, 2009
    Posts: 394

    from Motown

    Best to wait until you have the engine and trans ready to mount or you might be re-doing it.
    mgtstumpy and gimpyshotrods like this.
  3. jaw22w
    Joined: Mar 2, 2013
    Posts: 927

    from Indiana

    Too many variables in the equation to nail down pinion angle at this point in your assembly.
    gimpyshotrods likes this.
  4. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 5,812

    Bandit Billy

    I take it you haven't welded the perches to the axle yet. You don't need to be uber exact right now, just set it a couple of degrees up and tighten the u bolts, it will stay there. Weld it once you have the running gear where it belongs and body mounted and everything is at ride height.
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  5. At this point of what I see factory numbers no longer apply. The issue your having is common. Best advice is just work around it and keep moving forward. I'd set my pinion parallel to frame rails, get a dive shaft and set it on top of Yoke while slipped in the tailshaft and build what it needs for floors. A little surprised you don't already have the floors done with the frame painted.
    lake_harley likes this.
  6. Dirk35
    Joined: Mar 8, 2001
    Posts: 1,992


    You didn't mention what your transmission yoke is like. If its a typical Chevy Turbo 400 type, it'll have a splined shaft which is where you slip joint will be. If its like a Ford C6, you'll have a U joint cup at the end of the transmission and will need a slip joint in the middle of your drive shaft. You must have a slip joint either in your drive shaft (2 piece drive shaft), or a slip joint at the transmission. So you'll need either a Standard Slip - 2 joint, or a Reverse Slip - 2 joint shaft.
    Drive shaft types.jpg Drive shaft types.jpg

    Currently, your 3rd member looks like its sitting about 10-15 degrees up.

    For now, Id suggest that you do as Bandit Billy said. Tighten the bolts that hold the spring perches and set the pinion angle at 3-5 degrees. Put the engine and transmission in. Then measure and order your drive shaft. Don't weld the spring perches to the axle tubes until you actually get the car further along in the build. Then re-set your pinion angle and weld the spring perches once you get the weight of the body and rest of the car on the suspension. The pinion angle will change, but it shouldn't change the length of the drive shaft that much.

    This site has a great guide on how to order your drive shaft and will answer all of your questions. If this link doesn't take you there directly, Click on "Order/Price Quote" and it will take you to their 4 page measuring guide.
    Last edited: Sep 5, 2019
  7. thegearhead
    Joined: Nov 23, 2015
    Posts: 35


    Engine & Trans can be set in all mounts are made and i've had in it already a few times. The Driveshaft is a slip spline gm yoke. It's from a Vega i got to shorten it yet. The spring perches aren't welded yet i'll make sure to do that last of build. I guess i can rough it to angle and cut the drive shaft at the rear and when i slip it back into the pipe just place a small tack weld in case i have to shorten it more after all weight it is on the suspension.
  8. 1946caddy
    Joined: Dec 18, 2013
    Posts: 1,509

    from washington

    The first thing I would do is level the frame either by using blocks under the wheels or as I prefer, jacking the frame up on all four corners. Install the engine and tranny and set the pinion angle on the tail shaft of the tranny down 3 degrees. I would adjust as necessary at the tranny mount to get this setting. There will be no need to adjust this setting again.
    I would do as Billy suggests and tighten down the rear U bolts to hold the read differential at 3 degrees up. Set the car back down on the ground and you should be able to measure for your driveshaft and tunnel. After your car is complete, with your wheel and tire combination on it, I would use boards under the front tires to once again level the frame and then check the pinion angle. The angle should still be at 3 degrees at the tranny and now all you have to do is adjust the rear differential to 3 degrees up and weld the spring perches and your done.
  9. Joe H
    Joined: Feb 10, 2008
    Posts: 794

    Joe H

    Get a couple heavy duty ratchet straps and go around the rear axle and frame so you can compress the rear spring, just as if you added weight to the rear. Measure the pinion angle before and after you compress it to see how it changes once the springs are pulled down. You may find it doesn't really change. You really don't need to level the frame if you can do a little math and use an angle finder.
  10. A digital pro level is priceless. [​IMG] They read in .010 of degrees.
  11. Bandit billy got you lined out.
    That’s exactly the way to do it at this stage of your build.
    Get a 4” pvc pipe to mimic the drive shaft and build your tunnel around that.
  12. You also don’t want to do anything until you’ve got the wheels, tires, ride height all nailed down anyway.
  13. rooman
    Joined: Sep 20, 2006
    Posts: 3,794


    Why would you put boards under the front tires to level the frame? The frame rake has nothing to do with driveline alignment. If the carb mounting face on the intake manifold is at X degrees relative to the crank centerline the engine should be installed so that the carb is level at ride height and the resulting engine angle should be duplicated at the rear end (leaf spring wind up issues notwithstanding--see the other pinion angle threads). Also there is no such thing as "the pinion angle on the tail shaft of the tranny " --the only pinion angle is at the rear end.

    RMR&C and lurker mick like this.
  14. Rhetoric questions where that info does not apply.
    What do the guys running blowers set their engines at?
    If rake has nothing to do with it, then why use a level that operates in relation to the ground.
    What happens if it’s built level then someone adds a rubber rake?
    If carbs need to be level how does a vehicle go up and down hills?
    Pist-n-Broke likes this.
  15. Doublepumper
    Joined: Jun 26, 2016
    Posts: 514


    Probably been doing it all wrong, but I build and assemble everything first and save the pinion angle and driveshaft for last. After everything is done and sitting on the tires, I set final pinion angle and measure for the driveshaft.

    For those that don't know, Denny's Driveshafts (may be others), sells a slip yoke for truck T-400's that have (had) the bolt on yoke. No need for a driveshaft with built in slip joint assembly.
    Black_Sheep likes this.
  16. squirrel
    Joined: Sep 23, 2004
    Posts: 44,304


    Put the pinion 3 degrees nose up, relative to the top of the frame. Then mount the engine so it is 4 degrees nose up, relative to the frame. It will work.

    Sent from my Trimline
    Pist-n-Broke likes this.
  17. Black_Sheep
    Joined: May 22, 2010
    Posts: 1,072


    I prefer to set pinion angle with the finished vehicle sitting on the tires at the desired height.
  18. rooman
    Joined: Sep 20, 2006
    Posts: 3,794


    #1 Most street cars with blowers have carbs and having them level is usually a good idea

    #2 The angle of what connects the components (engine, trans, suspension) is irrelevant, it is the relationship of those components that matters.

    #3 Then the carb mounting face will not be parallel to the ground. And here were are back to the old adage of "Plan Ahead" (or put up with the consequences)

    #4 Having the carb mounting face level is not mandatory but if OEM manufacturers have been tilting the carbs in relationship to the crank centerline in an effort to keep them close to level to the ground plane in the most common driving situation I would think that it is probably a good idea to follow their lead.

    Once again none of this is set in stone--it is simply a good idea to optimize the package when building from scratch. 1946caddy's suggestion of putting the engine 3 degrees down with the frame level and then putting it back to ride height could result in the engine being either level or nose down depending on the suspension/rubber package--not a deal breaker but once again the best way is to is to have the frame sitting as it would be going down the road (hills and valleys excluded).

  19. So blower engine gets set at zero for level carb and everything else needs to be nose up for level carb. Then pinions get set at 0 only if there’s a blower and nose up to match the carb

    Rake matters but not if you’re using a level?
    3* tail down on the engine(unless engine has a blower) with chassis at 4* nose down gives a 7* engine set up if the chassis is blocked level on the table. ( btw That looks like ass when the engine is 7* to the firewall)

    Trust me, I know how to set up a driveline and the principles are universal but every build is different. I’m just pointing out the obvious discrepancy in these so called rules everyone spouts that lead to confusion instead of an understanding of the principles that ultimately will lead to clarity.

    Most of my driving has been in Ohio,,,
    90% or more is not level.
    5 years in Colorado on the east side of the mountains and a lot of that was flat till you needed to go west,,, then it’s all up hill on the way out and all down hill on the way home.

    The manufacturers have standard packages to fit in, interior cabin requirements, air cleaner to hood clearances, minimum road clearance, all sorts of standards that most get thrown out the window when it comes to hot rods and customs. If the factory set your GTO with a level carb then you’ll be wise to follow their lead on that GTO. But how did Henry Ford or Willys install their blown Hemi engines?
  20. The Shift Wizard
    Joined: Jan 10, 2017
    Posts: 1,653

    The Shift Wizard

    I understand you have your reasons for having to build in a certain order. Think about making your floor somewhat modular, with your tunnel a separate piece from the floorboards. use your best estimate for the hump, etc. Then worst case, you may have to tweak just the tunnel later on.

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