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Old 06-07-2010, 05:55 PM
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Transmission / pinion angle setup

I've been looking at websites and postings on pinion angle setup for a week and finally tackeled settong mine up today.
First, I built the chassis from the ground up, along with the entire car. It is a 1932 Ford pickup with a chevy 350 and Muncie M20 4 speed. I took it to two shows this spring and won two trophies. Not bragging here, just setting the stage for my problem.
I have only driven the pickup for about 200 miles even though I have been driving it for about 14 months. My problem is vibration at all speeds that seems a little worse if I am going up a hill.
When setting up the chassis, I set the carb intake level and set the pinion at 3 degrees up - - toward the front. After getting back from the show last weekend, I promised myself I would solve the vibration befor going to another.
I shold mention that I am running 14" wheels on the front and 15" on the rear, which makes the car sit at a healthy rake without having the "stinkbug" look.
Today, I checked the trans output shaft using an inclinometer on the yoke; it was sero degrees. I checked the pinion and found it to be zero degrees as well. I could tell by the paint on the four bar set up that the alignment shop had changed the pinion angle for some reason. I had that done about 2 years ago.
All the info I've been reading over the past couiple of days ALL reference the engine being set on a higher plane than the pinion. My car is the opposite. I welded the engine mounts directly to the boxed frame and welded in a standard X member with a trans mount.
I just finished lowering the trans mount to get 2 degrees down to the rear and adjusted the four bar using the bottom arms to get 2 degrees up on the pinion. The drive shaft goes up from the trans to the pinion at a 6 degree angle.
I test drove the car and the vibration seems a tiny bit better, but not much.
With the rear end higher than the engine/trans, should I be doing something different??
I'm more than a little discouraged right now but am hopeing to attend another show two weeks from now.
Sorry for the long-winded post, but I know most of the info is pertinent.
Thanks for any help you guys in the know have to offer.
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Old 06-07-2010, 06:19 PM
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Have you checked the driveshaft for runout with a dial indicator, with it installed in the car?? I am wondering if you have a problem with a pinion yoke that runs out too much, or slip yoke, or the shaft itself and u-joints. Just wondering if you have a run-out or balance problem.

Factory yokes have a pretty wide tolerance, I once checked five used pinion yokes just to find one good enough to use on my Nova with the 8.5" rear. Worst one was almost .050" runout in just this one part. Factory driveshafts aren't much better.

If the driveshaft has been altered, are the yokes in phase with each other??

Can't blame suspension angles for the problem if the shaft or yoke parts are not concentric with each other, so I would check the driveline for run-out so you know exactly what you are working with.
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Old 06-08-2010, 09:37 AM
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Thanks for the thoughts and ideas, I'll check for run-out as soon as I can - - maybe tomorrow. The drive shaft was built for me by Driveshafts Unlimited in Seattle. That was about 4 years ago. I'll get back to you with the dial indicater readings.
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Old 06-08-2010, 12:37 PM
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The relationship of the ds and rear pinion is a no-no in drive line design, i.e. (driveshaft and rear pinion meeting with both having positive angles. After you check your balance etc. try the following: put your trans back to where it was (0 deg.) ; adjust you rear pinion down 2 deg. and see if it improves, if not take it down a bit more and see if any improvement. Also if possible raise the trans up 2 deg or more with the goal being to at least zero out the drive shaft to rear pinion with whatever it takes to (cancel out)* front/rear pinion angles * (if it requires a rear bias of up to 3 deg down at rear pinion you will still be fine.

Last edited by 406 bug; 06-08-2010 at 12:45 PM.
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Old 06-11-2010, 04:46 PM
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OK; I couldn't get comfortable with my dial indicator readings so I had Drive Lines NW recheck the driveshaft and balance. They "dynamically balanced" it and checked the yoke and found it to be within tolerance.
I then reset the pinion from 3 degrees up to 2 1/2 degrees down and test drove the car for about a mile each way. The vibration was much better. I put it back on my lift with the intention of rasing the transmission up (it was still set at 0 degrees) to 2 degrees positive and found the bell housing would hit the firewall at just 1/2 of one degree. I need to notch the toe panel / firewall about an inch to get the two plus degrees positive on the trans. I built the chassis and set it up thinking I knew how to do it properly and then fabricated the firewall and toe panel to match the bell housing. I did that to get maximum leg room in the small cab. That will take me all weekend to accomplish. I really think 406Bug has it right.
I'll check back in to let you know how it went.
Again, thank you both for the ideas.

Jim
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Old 06-15-2010, 09:32 AM
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I could not get comfortable with my dial type angle finder, so before I cut anything, I spent $28 on a digital angle finder and rechecked what I had set up. I found I had 2.9 degrees down pinion angle, .9 degrees down on the transmission! I cut the toe board, firewall junction at the point the bellhousing was hitting and brought the trans up until it hit the floor panel. I ended up with .4 degrees up on the trans and then adjusted the four bar links in the rear to end up with .9 degrees down on the pinion. The drive shaft ended up near level at .2 degrees. The trans is still lower than the pinion by abut 3/8 th of an inch.
I crossed my fingers and buttoned everything back up and test drove it, taking a friend with me. The vibration is all but gone and my buddy said he couldn't feel any at all. Today will fabricate and paint the cover on the cutout and after drying, tack it in and seal it. You have to look hard to see the cutout at all. Reinstall the carpet and kick panels and be ready for the show this weekend.
Thanks for the input and I hope someone else will read this if they are having similar issues and learn something from it.
Jim
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