mixed info on setting pinion angle?

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challenger57

cuda57
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When setting pinion angle should the car be on jack stands under the frame letting the suspension hang or should the car be up on blocks. I have checked my angle with car on blocks under tires and I get tranny down 1.5 degrees and with 2 degree shims the pinion is up 1 degree. This all comes from after doing a auto to 4 speed conversion. After doing conversion I had a thud when starting to back up. One person said needs new leaf springs, did that no help. Another said pinion angle, hense the 2 degree shim. That almost got rid of it but does it still slightly. I have another set of 2 degree shims and was wonder about trying them but then pinion will be up 1.5 degree more than tranny. So what is correct method and thoughts on degree difference.
 
challenger57 said:
When setting pinion angle should the car be on jack stands under the frame letting the suspension hang or should the car be up on blocks. I have checked my angle with car on blocks under tires and I get tranny down 1.5 degrees and with 2 degree shims the pinion is up 1 degree. This all comes from after doing a auto to 4 speed conversion. After doing conversion I had a thud when starting to back up. One person said needs new leaf springs, did that no help. Another said pinion angle, hense the 2 degree shim. That almost got rid of it but does it still slightly. I have another set of 2 degree shims and was wonder about trying them but then pinion will be up 1.5 degree more than tranny. So what is correct method and thoughts on degree difference.
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I always heard and read , 2-3 degrees down compared to the rear of the drive line.
 
Pinion angle at tranny and rear end need to be opposite and equal. If tranny is down 2 degrees the pinion should be up 2 degrees. Also vice versa - if tranny is up, pinion should be down. This is with suspension loaded, not free hanging.
 
Car MUST be "on wheels" loaded IE gas fuel, spare whatever is "normal" driving loads.

There is room for "opinion" but the SIMPLE answer is that the CRANK CENTERLINE and the PINION SHAFT must be PARALLEL under full acceleration.

What this means is, that due to the flex of the leaf springs, there is some "flex" between "unloaded" (torque) and full throttle, and THAT is where you get the discussion about whether it should be 2* down, etc. The fact is it depends on spring stiffness, and "experience of others"

Of COURSE there are videos

https://www.google.com/search?q=dri...0rHMAhUO2mMKHWTqDrYQ_AUICSgD&biw=1138&bih=511




While you are at it, make sure the shaft is "built" correctly. "u joint phasing". The simple answer for these one piece shafts is that you should be able to look down the shaft like a rifle, and the end caps on both ends should be in perfect alignment. if not, the shaft is either twisted, or welded up incorrectly
 
You DO NOT want the a zero angle when static, loaded suspension.

If the trans is pointing 1.5 down, the pinion should be 1.5 up to be at zero. Roll the pinion DOWN 3* so it would be at 1.5* down on your angle finder.

Pinion angle
 
It becomes a little clearer if you think about your pinion snubber. If you are running one picture the angle your pinion will be in under load when it makes contact (if set correctly). If the yokes of the shaft and pinion are not in line you have a lot of horse power pulling on the cap straps or retaining bolts....
 
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When you accelerate the pinion will rise. This is a known fact. The drive train is happy when the engine drive line angle is equal to the pinion angle (under acceleration). So if your drive line (trans angle) is down 3 degrees your pinion angle should be down 2 to 3 degrees (down) more than the drive line angle so that when you accelerate they become aligned (equal). When you accelerate the pinion will rise (2 to3 degrees) depending on your springs so you always have to set your pinion angle lower than your trans angle.

Moparts on the Web - Main Index

treblig
 
Ok, I'm good on the load part but we have 2 diff. of opinions here. One is matching degrees up and down, the other is both down. I have read both down for racing but that is not my case, just street. Also my original problem as stated is in reverse not forward. Anymore thoughts???
 
challenger57 said:
Ok, I'm good on the load part but we have 2 diff. of opinions here. One is matching degrees up and down, the other is both down. I have read both down for racing but that is not my case, just street. Also my original problem as stated is in reverse not forward. Anymore thoughts???
Click to expand...

I think you are interpreting it incorrectly. Forget "up and down" Worry about the RELATIVE angle between the two shafts. If your car was floating in outer space, parked beside the Starship Enterprize would there be an "up" and down?" No. There is only relative to each other. When you are accelerating hard, under full or nearly full power, you want the shafts PARALLEL. The pinion will ALWAYS be "down" in relation to the crank centerline when "not" under power.
 
If the noise is only present in reverse, I would drop the chunk and look for a broken tooth on the gears.
 
Ok again, I need people to understand my issue is not going forward, just getting started in reverse. Going back to the beginning. After the tranny conversion I almost could not go in reverse at all due to the HARD thud the car made ( no shims at this time ). Adding 2 degrees on pinion up made it almost go away. Before I was 1 degree down below 90 degree, adding the 2 degree up gave me 1 degree above 90. Sooo should I add 2 more degree up giving me a total of 3 degree up or go back and add the 2 degree down for a total of 3 degree down?? The thought of a broken tooth has crossed my mine and is my last resort.
 
You're not making any sense?? The angle of the pinion means absolutely nothing without considering the angle of the drive train. You wrote, "Before I was 1 degree down below 90 degree, adding the 2 degree up gave me 1 degree above 90."

That statement means nothing without the drive line angle. Forward or reverse don't matter. Did you even take the time to look at the website I posted???


Moparts on the Web - Main Index

When you're in reverse the pinion will drop down towards the ground. You can't hardly get a vibration in reverse because you can't go fast enough to get a vibration??? And yes the car should either be on the ground or you should have jack stands under the rear axle to simulate the car on the ground (Car weight on rear axle).

Treblig
 
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The Mopar Performance Suspension manual that has been in print OVER FOURTY YEARS has all your answers in one place. Mancini sells them for $10 each.
 
challenger57 said:
Ok again, I need people to understand my issue is not going forward, just getting started in reverse. Going back to the beginning. After the tranny conversion I almost could not go in reverse at all due to the HARD thud the car made...................The thought of a broken tooth has crossed my mine and is my last resort.
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OK, I see

FORGET pinion angle. You need to pull the shaft and inspect the U joints carefully, then pull the axle apart. Pay attention to the brakes and axle bearings, IE each piece as you tear it down.
 
challenger57 said:
Ok again, I need people to understand my issue is not going forward, just getting started in reverse. Going back to the beginning. After the tranny conversion I almost could not go in reverse at all due to the HARD thud the car made ( no shims at this time ). Adding 2 degrees on pinion up made it almost go away. Before I was 1 degree down below 90 degree, adding the 2 degree up gave me 1 degree above 90. Sooo should I add 2 more degree up giving me a total of 3 degree up or go back and add the 2 degree down for a total of 3 degree down?? The thought of a broken tooth has crossed my mine and is my last resort.
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What else did you change? From which TF to what output size 4spd.? With the car's weight on the wheels(and the parking brake ON & chocked!), how far forward can you move the driveshaft taken
loose from the rearend? If you changed propshafts & it's too long,
it mite be butting the tailshaft.
 
No trebling I did not look at it earlier and now that I have it has much of the same info I have seen before especially the block pics of tranny and pinion angle comparisons and what they should be which is where I am at--tranny 2 deg. down pinion 2 deg up. When I get this figured out I will come back with my final results. Killer you must have chimmed in while I was typing. I did also replace the drive shaft with a new custom made that I know does not bottom out against the inside of tranny. went from stock 65 904 to a OD 4 spd.
 
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Last time... You never ever, EVER want the pinion and trans lined up when there is NO LOAD on a leaf spring car.

That's what you have right now with the trans 2 down and pinion 2 up.

See post #6 AGAIN!!!
 
Ok crackedback you are the winning solution to my reverse thud problem. I had initially used a 2 degree shim to tip the rear up which helped but not fixed. So under crackedback suggestion I flipped the shim around and tipped the rear down 2 degrees. Don't you know it worked, no more reverse thud. Thanks for everyones suggestions.
 
crackedback said:
Last time... You never ever, EVER want the pinion and trans lined up when there is NO LOAD on a leaf spring car.

That's what you have right now with the trans 2 down and pinion 2 up.

See post #6 AGAIN!!!
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Ok I tried it and you are the winner in fixing my problem. It seems to be the opposite of most articles I have read But it worked, I am now 2 degrees down by flipping the 2 degree shim around tipping the rear down. thank for your suggestion. Sorry about the double thanks I thought this one went directly to crackback
 
That's what happens when follow someones advice that actually knows what they are doing.

If you get that Mopar Suspension book, you will understand all the whys as to why it works that way and how good the Mopar suspension really is. It's an invaluable source of information that hardly anybody ever gets and once they do, they wonder how they ever got along without it.
 
Cool.

You should now have a -4* pinion angle. -4 is a little strong for a light duty street car, should be OK. Run it and see how things go. As long as you don't have any vibration issues, go with it!
 
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