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Thread: rack and pinion steering

  1. #1
    Join Date
    Jan 2007
    Location
    Evansville, Indiana
    Posts
    3

    Default rack and pinion steering

    Just curious if anyone has tried it.

  2. #2

    Default

    Just curious if you've ever owned a truck.



    Seriously though, there is a reason R/P is not the preferred steering on straight axle vehicles. Are you converting yours to IFS? Then it is the better choice.

  3. #3

    Default

    I install it on our mud racers all the time, but I cant say it would be good for a daily driver. I guess, I never thought about it.

  4. #4
    Join Date
    Jan 2007
    Location
    Evansville, Indiana
    Posts
    3

    Default

    This M715 is my first 4x4. I'm not sure I understand why r/p isn't preferred. Not strong enough?

  5. #5
    Join Date
    Dec 2003
    Location
    parsons Kansas
    Posts
    476

    Default

    Ill try this and correct me if Im wrong but r/p are designed to work with independent suspensions and are bolted to the frame and cant be bolted to the axle to work corectly, thuswhen the axle articulates it would throw off the steering centerline.

  6. #6
    Join Date
    Dec 2003
    Location
    Giddings, Texas
    Posts
    7,729

    Default

    Dave has the right idea. A rack and pinion steering system is much more precise than the normal recirculating ball system all our trucks came with. But, our system allows the front tires to be tied together with a tie rod and then a single part connects the tied together tires to the steering box (drag link). So, as long as the drag link ends are operating in the same plain, the wheels will still go the direction the steering wheel tells them too no matter what crazy angle the axle is at. Too high a lift and a drag link at 45 degrees finds the steering wheel pointing in one direction and the wheels changing that direction based on bumps and drop. But, it is only one angle to worry about, the drag links.

    A rack and Pinion is secured to the frame with each end of the rack tied to a wheel with tie rods. Those tie rods can't really exceed more than about 30-35 degrees of up and down deflection. This causes two major problems with solid axle 4x4 systems.

    1) The rack has to be lowered to keep it parallel to the axle. Both tie rods from the rack have to be at the same angle as the other one. The only way to make that happen is to have the rack hanging in front or behind the axle. Think of more stuff hanging down to get ripped off.

    2) The tie rods move in an arc when the suspension moves. Hold a pencil by the tip. Then move it up and down. The eraser end moves in an arc. If the tie rod was attached to the rear of the steering spindle, a tire at full stuff would be pointing out while a tire at full droop would be also while a tire at the middle would be pointing straight. Now, hold two pencils in one hand with the erasers pointing in opposite directions. Push them both up and your tires now look like that skiing dude on Wide World of Sports. The same goes for full droop.

    The only way a rack and pinion can work with a suspension that moves is with an independent suspension. Then, only when the rack is set precisely at the a point allowing the tie rods to move parallel to the upper or lower control arms on the suspension during suspension movement.

    Many years ago I found a 1937 Packard 120 Coupe. I got the entire rolling body/frame for $100. No brakes, no steering, nothing of any value beyond the body and frame. I also had a '78 El Camino with a 12 bolt rear axle and bad engine. They were exactly the same wheel base. You guessed it, the Packard body went onto the El Camino frame. The only problem was the El Camino had the steering box infront of the wheels. The Packard body basically stopped at the front fender. I had to get rid of the steering box. I found a Chevette with a brand new power rack and pinion. I "made" the rack fit to dimensions to make the body work and the steering linkage from the column work. I was close on the tie rod to A arm angle, but close wasn't good enough. Every time I drove that car if I hit a bump, the tires would point together during compression, be parallel during rebound and then point together again at the top of the suspension cycle. I moved that rack up and down and could get close, but never perfect with the angle. I ended up stripping it and selling it a few years ago. The gauges on my M715 were bought for and installed on that car in 1992. The engine is now in my '66K20.
    Remember if you didn't build it you can't call it yours.

    6.2 powered M715, 5 M1009's, M416, 2 M101's, 2 M105's, 3 M35's, M1007 6.5 turbo Suburban project called Cowdog.

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