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Thread: SBC/Tremec Transmission Mount Spacer

  1. #1
    Senior Member MBB Larry's Avatar
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    SBC/Tremec Transmission Mount Spacer

    Trying to determine the Transmission Mount Spacer dimension to get correct Alignment/Clearance for the Drive Shaft. I temporarily just set the Yoke on a 1/4" piece of plywood to get an approximate height. How critical is this dimension. I did modify the SBC Engine Mount to clear the Front Pulley by machining Bushing to move the Engine back about 1/2">>

    trans.jpgengmt.jpj.jpg
    FFR Hot Rod #1106

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    Seasoned Citizen NAZ's Avatar
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    Larry, adjust your trans mount for the clearance you need. The important thing is that the trans output shaft and the pinion angle match under acceleration. You will adjust the pinion angle to achieve this.

    Typically the OEMs will set the engine & trans on a slight angle (trans output shaft angled down) and the pinion shaft will be angled up (in front). And since they use elastomer bushings on the control arms (or IRS third member) that angle will be a few degrees different to allow for axle rotation under load. As the torque is applied to the axle during acceleration it will tend to rotate (pinion will move up in front) as the bushings flex under load. How much? Everyone will have their own idea but to determine this precisely will require some experimentation for your application. But most folks go with 2 or 3 degrees (whatever the consensus is) and call it good. That's 2 or 3 degrees less pinion angle as remember it will increase under load.

    BTW, I took a similar approach with spacers on the motor mounts to move my SBC to the rear. And of course this affects the driveshaft length required.
    33 Hot Rod Super Pro Drag Racer
    33 HR NHRA Cert Roll Cage Build

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    Senior Member MBB Larry's Avatar
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    Thanks Naz, I think I got it. I was trying to level the car with the shocks to get an idea of the entire set-up. As I am using a Carburetor, I was trying to get the Carb in a level attitude by tilting Transmission. I think that is not so critical. And the Leveling of the car does not effect the 2-3 degrees Pinion Angle. Correct?? On the Drive Shaft, I have Dan's 4-Link Suspension to center the Wheels in the Rear Bike Fenders. I am waiting on the New Generation Body I ordered. With the New Body on my Frame (A Generation 1.5!?!?!?) I want to get the Wheels centered, then get my Drive Shaft cut and Balances. I ordered a longer Driveshaft with my original order. My frame has several mods from FFR, but I am told the Wheel Base remains the same???? I believe the original Wheel Base is +- 112" and to center Wheels you need about +- 113"??? If I want a 1" float in Yoke, I was going to determine this last. Does this all sound like the way to go??
    FFR Hot Rod #1106

  5. #4
    Seasoned Citizen NAZ's Avatar
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    To recap:

    Leveling the car and then adjusting the angle of the engine / trans with the trans mount to make the carb set level (your carb mounting pad should be angled down in front around 2 - 3 degrees) is good as long as you have adequate clearance for the u-joint at the trans. If not you may have to adjust the height of the motor mounts too but thats not a big issue. It's good to have the carb level but a degree or two on the carb angle is not a problem. And you're correct, this won't inhibit you're ability to adjust the pinion angle for the angle set on the engine / trans. The pinion angle is adjusted to the trans output angle regardless of the angle of the chassis.

    I centered my rear axle in my rear fenders and now have a 113" wheelbase. And I had a custom driveshaft made after the driveline was all adjusted.

    Sounds like you're moving along nicely. Since this is a new version of the HR it would seem prudent to get the body mounted and make sure the rear axle centers in the rear fenders like you expect before ordering the driveshaft. That way there will be no costly surprises.
    33 Hot Rod Super Pro Drag Racer
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    Senior Member MBB Larry's Avatar
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    Thanks Naz, I will do that. Supposed to arrive mid February. I'll post some photos and progress reports. Going to Europe next week for 5-weeks. A break from the car. I do plan to put a program together, and some research. I bought an American Autowire Kit from Dan. Taking Diagrams, and all my Electrical Options and design some kind of plan.
    FFR Hot Rod #1106

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