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Technical Pinion Angle

Discussion in 'Traditional Hot Rods' started by Johnny 28, Nov 4, 2018.

  1. Johnny 28
    Joined: Oct 27, 2018
    Posts: 7

    Johnny 28

    I'm mocking up my 28 model a ford tudor frame . Right now with all the tires on that I'm using and the engine where I want it . The rear end and the transmission center lines ended up the same. My question is should I lower the transmission and roll the rear end down or leave it this way?
  2. tfeverfred
    Joined: Nov 11, 2006
    Posts: 15,793


    Try a search. There are a lot of good threads on this topic.
  3. Jimmy2car
    Joined: Nov 26, 2003
    Posts: 1,707

    from No. Cal

    The only drawback to leaving it the way you have it now, is that the U-Joints wear out quicker because they don't get the exercise they would normally have when the angles are different.
    I left mine and have had no trouble
    trollst likes this.
  4. Some questions. Is your engine level? Are you saying your driveshaft is level? Are you saying your rear axle tube CL is level with the trans output shaft?
    Last edited: Nov 4, 2018

  5. The Shift Wizard
    Joined: Jan 10, 2017
    Posts: 2,051

    The Shift Wizard

    The problem with most of the threads on pinion angle are some very talented and qualified experts use descriptive words about the angles but with opposite meanings for those words. So they argue post after post when they are actually meaning the same thing. For example, they make their sketches, engine on the left, rear axle on the right, one half of the experts look at the axle as the center or base (like on a clock face with the pinion end being the hour hand) and if the pinion tip needs to be pointed up 3 degrees toward the floor pan (3 minutes after 9, 9:03 o'clock), they call that "pinion angle up 3 degrees". The other half of the experts finger walk from the front of the car to the back so the first thing they poke with their finger is the pinion end or yoke. From there, the axle center should be downhill 3 degrees so they call that "down 3 degrees". It's the same thing but they name it the exact opposite. Anyone checking threads for info needs to be able to interpret which opposite meaning each side of the argument is giving the same words.
    Now that I've cleared that up for half of you and further confused the other half..... Good luck everybody! :p
  6. Basic rule. Engine up 3 degrees up front pinion up 3 degrees.
    421-6Speed and ironworker95 like this.
  7. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,511


    Pinion and tail shaft center lines need to have equal, but opposing angles when viewed from the side (aka: parallel lines, preferably not co-planar), and parallel center lines, even if not co-planar, when viewed from above.

    So long as the angles are not excessive (greater than about 4º), and are not 0º, it will be totally fine.

    If your angles are 0º, in static operation, grease would not move around much in the u-joints. That would either decrease u-joint life (20,000 miles v. 60,000 miles, oh no!), or require you to grease more (oh no!).

    Assuming that you are not going to simply run the car on stands for its entire life, the cycling of the suspension over bumps will take care of moving the grease around. Just remember to squeeze in a little fresh grease twice-a-year.

    If you have to put fresh u-joints in every few years, is that going to ruin this for you?
  8. pitman
    Joined: May 14, 2006
    Posts: 4,962


    I always aim trans tailshaft down 3* and pinion up (at front, in sideview), or you can obtain some offset due to trans tailshaft on C-L, with pinion offset, depending upon rear diff. (Measure at ride height)
    Last edited: Nov 5, 2018
  9. Johnny 28
    Joined: Oct 27, 2018
    Posts: 7

    Johnny 28

    Thanks for all the input. I haven't made the transmission mount yet and can put the angle where needed . Right now I'm at +2 degrees. Also the rear end is not fixed and I'm using hair pins and coil overs.
  10. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,511


    2º is just fine.
    Johnny Gee likes this.
  11. You've got that right, Wiz. I already see two posts that are either inaccurate or stated incorrectly, and we're still one page one.:eek:
  12. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,511


    Prove me wrong.
    pitman and V8 Bob like this.
  13. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,650

    V8 Bob

    The U-joint working angle is what is important; simply pointing the tranny down/pinion up 3 degrees may well exceed the recommended 3 degree maximum working angle, depending on tail shaft height in the chassis compared to the pinion, and/or length of drive shaft.
    Most important is to have the rear axle set at the desired ride height in the chassis to establish accurate U-joint angles.
    alanp561 likes this.
  14. ironworker95
    Joined: Oct 26, 2015
    Posts: 23



    Sent from my SM-G930V using The H.A.M.B. mobile app
  15. No need to ..Don't disagree here.
  16. Good post
    alanp561 likes this.
  17. Nothing seems radically out of line per Op's statement within question posted. "The rear end and the transmission center lines ended up the same." It is almost save to say work on engine and rear angles and disregard drive shaft since it "appears" to be at 0 degrees from level currently. I'd predict that if Op raised front of engine to be 2 degrees and rear yoke up to be 2 degrees the drive shaft "may" end up, up in the front by 1 degree and down by 1 degree in the back. Do the math.
  18. Johnny, Here's where I was confused, from the start.
    You said in the beginning that the trans ( engine /crankshaft) and rear end all ended up in a straight line. But then you mentioned 2 deg.. So then ,where did the 2 deg. come from?
    Last edited: Nov 5, 2018
  19. Fat47
    Joined: Nov 10, 2007
    Posts: 1,240


    OK, so which is it? Tranny up 3 deg. and U-joint up 3 deg. OR Tranny down 3 deg. and U-joint up 3 deg.
  20. Smokeybear
    Joined: Apr 20, 2011
    Posts: 325


  21. I have been using 3 degrees down for setting engines since forever. Or get the carb flange level works too. For disposable bomber stock cars, we'd lay the engine and transmission in, weld the mounts to anything handy using anything handy. It wasn't always pretty.
  22. That's okay , if the vehicle is set up like in your diagram (pinion / axle center line higher than the trans output)
    Should be fine for hot rods, lowered cars, etc., but lots of cars and trucks aren't built that way.
    In my opinion, the only 3 deg. rule you can state positively is 3 deg. OPPOSING angles. How you get there depends on many factors.
  23. Exactly . . . like having a Ford 9" rear in the back with the housing centered and the pinion offset . . .
  24. 421-6Speed
    Joined: Dec 10, 2011
    Posts: 451


  25. Like stop looking at the drive shaft as it needing to be level or tipped down toward the rear and concentrate only at the angles where the u joints meet the drive shaft to get the correct Z pattern. Hell but a wedge between the carb and intake if need be so the carb sit's right so it all ends up working.
  26. Johnny 28
    Joined: Oct 27, 2018
    Posts: 7

    Johnny 28

    HI Marc. The engine and transmission are in mock up stage . When I took the two measurements I hadn't checked the degree of the transmission yet. None of the mounts for the engine and transmission are finalized. I can still raise the front of the engine to take some of the 2 degrees out. The engine is where I wanted it for height . But it looks like I'll be adjusting this . Thanks
  27. Joe H
    Joined: Feb 10, 2008
    Posts: 930

    Joe H

    Be sure to add weight over the rear axle or use ratchet straps to compress the rear spring(s) to simulate full body weight. Its pretty much a waste of time setting driveline angles with out full weight on the chassis.

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