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Old 01-13-2011, 06:42 PM
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pinion angle up or down?

balanced driveline today, and helped some, but have a small vibration between 25 thru 45 checked pinion angle and looks as follows.
trans. 5 degrees down, and pinion 3 degrees up. I have been watching
comments here about how and what to to do with a good pinion angle.
One site seems to say it is prefered to have an angle on the pinion slightly
down. What do you think of my current angles and how do figure what total
angle I have at the present. Thanks.

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Old 01-13-2011, 06:55 PM
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Pinion angle depends on the cars rear end configuration. Leaf springs, leaf with traction bar, ladder bar, coil, coil with traction bar, 3-link, 4-link, etc.
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Old 01-13-2011, 07:13 PM
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For just basic starting point they should be in parallel planes . Same angle up on pinion as transmission is down. This is the cruising angle . It will change under hard braking or hard acceleration so if it is for a drag strip it would be different because of suspension flex.
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Old 01-13-2011, 07:26 PM
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Most performance rear ends will be set up either even or a few degrees "down" so the pinion angle will become even under hard acceleration, but it does matter what type of suspension is being used.

In performance apps, I believe leaf sprung rear ends "like" the most downward pinion angle (like 3-4 degrees), coil sprung cars somewhat less.
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Old 01-13-2011, 08:17 PM
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Quote:
Originally Posted by cobalt327
Most performance rear ends will be set up either even or a few degrees "down" so the pinion angle will become even under hard acceleration, but it does matter what type of suspension is being used.

In performance apps, I believe leaf sprung rear ends "like" the most downward pinion angle (like 3-4 degrees), coil sprung cars somewhat less.
You did like to play at the dragstrip, in a past life. LOL
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Old 01-14-2011, 09:12 AM
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Thanks for the response. I have stock leaf springs on this 56 chev. My measurements with trans.4 down and pinion 3 up should cancel each other,
and be near 1 degree offset if I`ve got the princible correct. My vibration between 25 and 45 mph is not bad, but would like to get it smooth at all speeds. I kind of doubt that tire balance in these speed range would cause the vibration, but I`ve been wrong many times before. And by the way, one member asked if I, like so many others on this site were past Drag boys.
Yes, Burdick Bros. "Bluebird" blown 426 hemi. AZ. CA. mid 1960s - 1970.
I was the driver, my brother the master mech. thats why I`m asking these pinion questions, ha. Thanks for listening.
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Old 01-14-2011, 09:29 AM
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i have found, that often a drivetrain vibration will be there at all speeds.
tire balance vibration is often only at certain speeds and will go away as you speed up or slow down.
i would have the tires rebalanced (most places do it for free anyway )
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Old 01-14-2011, 09:55 AM
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Quote:
Originally Posted by db flyer
...Burdick Bros. "Bluebird" blown 426 hemi. AZ. CA. mid 1960s - 1970.
Sunday!... Sunday!... Sunday!... Beeline Dragway... Be There!... Be there!... Be there!...
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Old 01-14-2011, 10:12 AM
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Quote:
Originally Posted by db flyer
My vibration between 25 and 45 mph is not bad, but would like to get it smooth at all speeds. I kind of doubt that tire balance in these speed range would cause the vibration...
Have you tried things like putting the trans into neutral at the speed of the vibration to see if it went away? Or if it vibrates more while at coast or 'floating', or when accelerating or decelerating? This can help to tell if the vibration is driveline related or not.

I wouldn't automatically dismiss tire balance as being the cause, even at those slow speeds. If the tires are at fault you'll get the vibration in neutral or in gear. If you didn't want to rebalance them, you could swap the tires front to rear if they're near the same size to see if this changes things.

If the U-joints were replaced recently, the drive shaft might be out of phase if the shaft wasn't reassembled as it was originally. You can even get a vibration if the joints are worn.

Usually axle bearings will give you some noise if they're badly worn, but if the axle has enough radial play, the harmonics could be such that you'd feel a vibration.
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Old 01-14-2011, 10:40 AM
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Thanks for the info , I will check things further.
Beeline dragway, be there! ya! ah sweet memories.
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Old 01-14-2011, 12:12 PM
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Quote:
Originally Posted by cobalt327
I want to wax nostalgic for just a minute, I hope you will indulge me.

As a kid, I grew up in a junkyard. I don't mean I visited a JY often, I mean I actually grew up less than 20 yards from around 550 cars (more or less) in a 40 foot x 10 foot trailer w/my parents and older sister. Because of an injury, my Father had lost the use of his left leg. Non union break of the femur right at the ball. Today they'd have done a hip replacement, alas that was years in the future, so he was left w/me to be his "left leg".

The one thing I LIVED for was the rare weekends that my Dad and I (sometimes w/my future brother in law in tow) would be able to go to the 1/5 mile asphalt bullring in Taft, FL for the races, or better yet, to the drags at Valkaria, FL.

The first nitro dragster I saw I very nearly peed myself! I AM NOT kidding. We were mere yards from the track, back then safety was an afterthought, and the pipes used were called "weed burners" (zoomies had yet to be invented). The noise was AWESOME! The smells, sights, even the taste is still w/me to this very day.

I vowed then, that as soon as I was able, I would be out there, and I did- w/a vengeance- given my limited budget for racing.

Those rare, exciting, heady times made up for all the sweat, busted knuckles and skinned arms and fist fights that a kid of eleven finds himself in when he's the "kid from the junkyard".

I'm NOT bemoaning this- I have come to terms with it for the most part, although old ways will still sometimes surface. It is the why and who I am. Some folks will never know what I'm talking about, and that's OK, too. I don't know what it was to grow up the way many others did, either.

I hear ya man! The first time I went to dirt circle races my uncle took my in the pits. The sound of BIG cammed modified, and the smell of Methanol...mmmm grape....hung with me my whole life! Every time I went to the races I was a nut for about a week! Finally I got my chance to get me a car, and to go in circles with the rest of the guys.

Still now when I get on the track, there is that moment before I roll into the throttle where my brain kinda goes "...here WE GO!!!!!" and I get this HUGE smile across my face.

I was standing by the side of the track at the last race I ran, waiting for my feature watching the IMCA modifieds hit the track. I was at the start of turn 1, and how the track is, you see the cars come out of four, MASH the gas, scream down the front straight. And right as they get to you the guys lift the throttle, THROW the car into the turn, then mash the gas again! Such a great thing to witness....then you realize, there are people in these cars! People that have that kind of talent and devotion to this sport, that they have risen to this ability of car control....it nearly brings a tear to my eyes!

Kinda sucks that, most likely, the next generation of kids wont get to race circle dirt out here...or at least in the cost friendly classes that I run...sad day.
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Old 01-14-2011, 06:30 PM
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I was chasing something similar for some time, thinking it was in the driveshaft, or tire balance, or pinion angle, or some such. Then one day while the trans was in Park, I brought the engine up to 2000-2200 rpm and there was that little vibration. Aha. Not tire balance, not the driveshaft, not pinion angle. So I unbolted the torque converter from the flexplate, made sure the converter would not contact the flexplate, and started the engine. Brought it up through most of the RPM range, and no vibration.

Long story short, replacing the flexplate, which had a .038" runout, plus replacing the torque converter (looked like a weight was missing but not sure) pretty much fixed the problem.
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Old 01-14-2011, 06:34 PM
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Well, I had my tires balanced today and the vibration is still there. So far I have rephased and rebalanced drive line a ta good shop, driven at many speeds and put in neutral with no difference. I hear no noise at wheel bearings or rearend so think that my trans. change from a 3 speed stick to the current th350 auto has changed the pinion harmonics. My angles which are 4 degrees down at trans. and 3 degrees up at pinion are probably the cause. I guess I need to try some shims under leaf spring pads. Dont know how much to start with, I guess I`ll try to shim down a little. Thanks
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Old 01-14-2011, 06:41 PM
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Thanks for info cucumber1949, I hope I dont have to replace both those items, but I can see the possibility of that being my case too.
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Old 01-15-2011, 07:12 AM
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Quote:
Originally Posted by cobalt327
I want to wax nostalgic for just a minute, I hope you will indulge me.

As a kid, I grew up in a junkyard. I don't mean I visited a JY often, I mean I actually grew up less than 20 yards from around 550 cars (more or less) in a 40 foot x 10 foot trailer w/my parents and older sister. Because of an injury, my Father had lost the use of his left leg. Non union break of the femur right at the ball. Today they'd have done a hip replacement, alas that was years in the future, so he was left w/me to be his "left leg".

The one thing I LIVED for was the rare weekends that my Dad and I (sometimes w/my future brother in law in tow) would be able to go to the 1/5 mile asphalt bullring in Taft, FL for the races, or better yet, to the drags at Valkaria, FL.

The first nitro dragster I saw I very nearly peed myself! I AM NOT kidding. We were mere yards from the track, back then safety was an afterthought, and the pipes used were called "weed burners" (zoomies had yet to be invented). The noise was AWESOME! The smells, sights, even the taste is still w/me to this very day.

I vowed then, that as soon as I was able, I would be out there, and I did- w/a vengeance- given my limited budget for racing.

Those rare, exciting, heady times made up for all the sweat, busted knuckles and skinned arms and fist fights that a kid of eleven finds himself in when he's the "kid from the junkyard".

I'm NOT bemoaning this- I have come to terms with it for the most part, although old ways will still sometimes surface. It is the why and who I am. Some folks will never know what I'm talking about, and that's OK, too. I don't know what it was to grow up the way many others did, either.
We have a lot in common.My dad had an ESSO station and wrecker service in the early 60,s.There were about 350 junk cars in our back yard.I just loved playing in those old cars and I guess that's why I have been in to old cars my whole life.Our house wasn't as small,28'X32' but we had 7 of us plus mom and dad and only 1 bath room.My dad's friend worked a the local drag strip and at 13 he started taking me with him.Man did I enjoy that.A lot of great old times.
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