chassis/Drive train set up question

[BERT]

Hello I have a 71 nova ,sbc 625 hp, I've changed over everything in the drivetrain, Trans=PG, Drive line= 3.5"DOM W/1350 joints, Chris alstons 9", Cal Tracs split leafs and Cal Trac bars, 10.5" MT slicks. to set up the pinion angle I measured the crank shaft/trans center line angle and the pinion angle with the driver in the car and the weight of the car on the tires. I foumd them to be within 1/2 degree of parrallel of each other ( the half degree was negative or down at the pinion ) the drive line working angle is 5 degrees. I've installed 4 degree pinion wedges to get more negative pinion angle which puts the pinion angle at about 4 1/2 degrees negative. With the drive line working angle at 5 degrees and the pinion angle at 4 1/2 degrees negative with respect to the trans center line angle it put the rear u joint angle total at 9 1/2 degrees static. Does this sound correct?

[BERT]

am i way off on this? hmm.... Will anyone with chassis experiance please share their method of setting up these angles. Thank you in advance - Albert

[Awesome Bill]

Take the pinion angle and subtract drive shaft angle with you sitting in the car @ race condtion and weight. No more than 4° neg. Anything more you just eat up power and loose e.t. Easy as that. I would personally only run 3° but you can do what you like. Cal tracs can work from 0 to 6° but it is not necessary. At this point, the leaf spring is just that, it does not affect the chassis with the cal trac doing the work. The hole position up or down will change little also. We have a Real 3550 72 Nova that will put the bumper on the ground, (rear) with Cal tracs and 295 Radials. So, there is a little more to just putting them on a flimsy unibody car and expect them to work. Our car has a complete roll bar with all important bars welded correctly to make the car a full frame. That is also with a 434, closed exhaust just as he runs it and drives it on the street.

[MACKRACING]

my78camaro has 12degrees neg i ran a 10.92@122mph. how kwick do ya thank my car would be with 3degrees neg?

[want-a-be]

my78camaro has 12degrees neg i ran a 10.92@122mph. how kwick do ya thank my car would be with 3degrees neg?

What rear suspension are you running?

Don

[MACKRACING]

12bolt with strange spool axles .i twisted the pumpkin up.had it jacked down.and the axle tubes welded.stock leaf,and ssm lift bars 50 50 shocks, on fronti have 90/10,trick springs,no traction problems,and1.45 60 foot.

[BERT]

Thanks for the reply bill! - Al
I edited for spelling

[Awesome Bill]

It is impossible to have 12°. Your measuring wrong? Your drive shaft would be into the yoke. The only reason you rolled the rear is because your fasteners were loose!

[MACKRACING]

i measured with a bubble gauge angle finder the rear end yoke were the drive shaft u bolts bolts to,10degrees down,measured the drive shaft,2degrees down,measured trans pan 0degrees.and the drive shaft goes inside the top of the rearend yoke when rotated.the spot welds in the pumpkin and axle tubes gave way.

[Awesome Bill]

just as I thought, your doing it wrong!

[MACKRACING]

so can someone tell me how to do it the right way!?

[Dart Vader]

so can someone tell me how to do it the right way!?
Thats crazy talk!!

By the way... I've moved this over to the Chassis and suspension forum.

[Awesome Bill]

Pinion angle is measured this way

you take the pinion angle and lets say it is 4° down, then you measure the drive shaft angle and say that is 5° up, subtract the 2 and you get 1° positive pinion angle, so when you hit the gas, the rear rolls upward of 4° and you now have a positive 5°+ pinion angle. The hp is lost between the universal joint rolling over itself and eating up power and causing the chassis to unload. It is unnatural for the pinion angle to be anything over 0° and work. The further you go the worst it gets.

that is why 3-4° pinion angle with a ladder bar set up puts you close to where you want to end up. 1-2° with a 4 link. Just finding out where you are first and then measuring correctly is the key. The car should be on a front end alignment rack with driver in it. measure like I said and subtract the drive shaft angle from the rear. Simple as that!

[Bad Influence Racing]

I know I will catch flack for this, but I don't agree with any of it. How I measure pinion angle, and have for many years is this. Remove the driveshaft and measure the angle at the yoke, just on the pinion. Measure it with a driver in the car at race weight. That is your pinion angle. The objective here is to get the pinion angle to be directly inline of the driveshaft when the car launches. Only problem here is there is no way of knowing what it will be on launch and no formula will tell you this. Adding and subtracting angles from crank centerlines and driveshaft do nothing, as the rearend is what influences the driveshaft angle. Subtracting one from the other does nothing if you think about it. If you get a measurement of -4 at the pinion, how does it become anything different when knowing what the driveshaft is? Pinion angle is just that, angle of the pinion. When the car launches, the pinion goes higher. The best scenario has the pinion angle inline or 0 upon launch. If it goes into positive numbers, it will slow the car down. If it measures -8, the suspension doesn't move that much to get it near 0, or inline. There is no magic internet formula of knowing where the angle of the pinion will be when each car launches. What angle it should be is just a starting point, and should be adjusted accordingly after each pass to net the best results. Good starting points are as follows.
1: Stock suspensions with rubber bushings, with no bolt ons should start at -6 and tighten up after each pass. -4 tends to work very well.
2: Modified stock type suspensions with solid bushings and bolt on bars can start at -4 and work your way up, these tend to like -2 since everything is solid.
3: Ladder bars and 4-links can start at -2, but since there is hardly any movement with these, they can be adjusted from -2 to 0.
All this is measured at the pinion only....
Every car is different and again these are just starting points, but since the pinion influences the driveshaft, there is no reason to know the rest of the angles and have to add and subtract. I have proved this time and time again, and when done this way, always nets the best results. There is no magic number for everycar, and you will have to adjust for best results. Not looking to debate, just letting you know what has worked the best over the years. Any questions, feel free..

[want-a-be]

How I measure pinion angle, and have for many years is this. Remove the driveshaft and measure the angle at the yoke, just on the pinion. Measure it with a driver in the car at race weight. That is your pinion angle. .

In reference to what,...the ground? I've always been taught, and have had very good luck with, measuring the difference between the pinion and the drive shaft. The pinion couldn't car less as to how different it is from the ground. It's not the ground that will put things in a bind if the pinion angle is wrong,...it's the difference in angle between the drive shaft and the pinion.

Not arguing, nor wanting to, just voicing my difference of opinion. :o

Don :cool:

[Bad Influence Racing]

That's fine, but why reference it to something that is influenced by the pinion? The angle of the driveshaft is just going move up with the pinion when the car launches. Referenced to the ground at the pinion only, if everything else in the suspension is right, is fine. You obv need to be on flat level ground, just like with any other measurement..You also start the lower control arm level with the ground as well? No? Provided the ride height and everything else is correct, the car is at the starting line, level..so why couldn't the pinion be referenced off of it? It is trial and error, since there is no way to know what each car has to be..what I listed are good starting points. Even if you add, subtract, multiply and divide from all other angles, and you come up with a -1 lets say, yet the pinion is really at +2, the pinion will go into positive numbers regardless of where the driveshaft is..which is not what you want. If you start at the pinion only, and make a run, and adjust it 1 degree at a time, until power falls off, what it is measured at the pinion is what it is...However, it all is defeated if the driveshaft is pointing UP as it goes back, which is not good. Making sure it is pointed down, I can understand. But knowing the angle doesn't matter..

[want-a-be]

The way I am looking at it is like this. Take the driveshaft off and it will never be able to get in a bind. Because there isn't anything to bind with. The way you are explaining it, if you are setting up the pinion angle on an incline, or decline, then that could bias your pinion angle settings. Because you are using the ground as the reference. But the difference between the pinion angle and drive shaft angle will always be the same, well, while the car is static that is. Shouldn't matter if the car is parked on a hill or not. That difference will always be there. It's the difference between the pinion and the drive shaft that will set up the potential for any binding.

Don

[Bad Influence Racing]

I think we will agree that you should always set the car up, regardless of what you are doing, on level flat ground. Doing it on an incline or decline would be pointless when trying to adjust anything with the suspension, no? With that said, while the car is on level ground, if you measure just the pinion, use a starting point, depending on the suspenion type, and work from there after each pass, you will find where it wants to be, regardless of any other angle. If you measure the shaft angle and add, multiply or subtract what the pinion angle is, you come up with a false reading. You can come up with -1 when the pinion is really at -4. Doing it the way I have done for years, just knowing what the actual pinion is, you will not get a false reading, and you know it won't go into positive numbers. No racetrack has a starting line that is going uphill or downhill, so you know what it will be at. If you start, lets say at an actual -4 and adjust a degree each pass, you will see a difference in how the car runs, and you will get to a point where it will slow down. You then back off to where it ran the best and your set. Same holds true for adjusting bars and instant center. I think by taking into account other angles just gets confusing. I have seen guys so it by measureing other angles and the pinion winds up going positive even though after their math it says the pinnion is negative whatever...For example, doing it off the shaft, let's say it is at a -5, and the pinion is -4, that would mean you have -1 pinion angle??, when in reality it is -4. Now if you are aiming for -4 pinion angle that would mean you would have to move the pinion way out of whack to achive that -4 when in reality it will be like -9 at the pinion, which is way off...Pinion angle is just that, angle of the pinion and that is all that should be measured. Again, I am not telling you or anyone what to do, just a cool friendly debate..:D I am just stating what works for me and has worked over the years and when I come across guys that have done it the way you are saying, the cars run much faster..Hope I didn't confuse you much?

[want-a-be]

Well,... sounds like we are both set in our ways. If my feeble memory serves me correctly. I was taught this by a guy who has won a few Wallys over about the span of about 35 years of running on the NHRA tour. Dominated the old Modified Eliminator in the 70s Switched over to Prostock in 1980. Won a lot of Prostock races, and maybe 4-5 Prostock championships back to back.

When he found out I was setting the pinion agnle like you are I got a 3-4 hour lesson on how chassis work. So until he tells me I'm wrong, I'll continue setting the pinion angle the same as I now do.

I do have one last question for you though. When you have bind due to poor pinion angle,...what is the pinion actually binding with?

Don

[want-a-be]

Kris,

I was hoping to get an answer to my last post. If I'm doing something wrong I'm wanting to learn why, and correct it.

Don

[Awesome Bill]

Kris,

I was hoping to get an answer to my last post. If I'm doing something wrong I'm wanting to learn why, and correct it.

Don

Don, How long have we been doing this. The mere fact that he does not fully understand what happens on the hit or launch, just makes it even more difficult to explain. You explained it near perfect and if he thinks his way is right, then I would not try to make him believe anything else.

Your post was near perfect, what I do care about is other people thinking his way is corrrect. So I will add something to maybe get wheels thinking.

The drive shaft in the front of the rear, the part that is solidly mounted to the car because of the transmission mount is not going to move and the angle is fixed in the % of degrees on the lauch. The angle @ the tranny moves very little and gets more movement as it gets to the back of the car. The longer the drive shaft, the more it will tend to move downward on the launch. Also, the amount of torque, gear ratio, tire size, suspension type etc all play a part in how many °'s the pinion angle should be.

Nitrous cars, blower cars all have a tremendous amount of torque. If you have a stock suspension chassis with a stock 4 link or leaf spring with some type of traction bar, you better have pinion angle or you will overrun the rear universal joints ability to roll over center when the rear starts its normal travel.

This opens up another area that has to be explained because some people do not think the hit on the chassis just takes the hit. When power is transferred threw the drive train, it all stops at the pinion gear. It trys to run the ring gear and just keep going. The axles and slicks along with the rear traveling downward transfer the torque to the sidewalls of the tire. ON EVERY HIT OF POWER, THE REAR MOVES DOWNWARD AND IF YOU DON'T THINK SO, CHECK A SLOW MO OF A LAUNCH OF A CAR! This will prove me correct.

Now if the rear is mounted with ladder bars, or a four link, the length of the bars actually only allow so much downward motion before the car moves forward. Even some downward motion will cause the rear universal joint to move downward being it is on 4 mounting points. 2 for the front of the ladder bars and 2 for the shock points to control the hit. As the rear moves downward because the rear tires and the side walls shorten up on the hit. This will cause the drive shaft to pinion angle to increase. If you start with a positive angle, seeing the actual pinion angle is above the invisible drive shaft to pinion line, the rear because it is locked to the chassis will rotate downward causing the pinion angle to actually move upward. Any time the pinion angle to the drive shaft angle goes into a positive #, you loose power threw the drive train. The idea angle is 0 under the hit of power to keep the drive shaft and pinion in a perfect non binding line.

With a 4 link, or ladder bar set up, you can control the hit of power way easier. You take a stock suspension 4 speed car without any traction control devices and you will have a drive shaft come way over center on the hit and chunk itself right out. Everyone has seen this many times. Why? because on a stock suspension car, it was never designed to be drag raced with a dead hook and tons of power. That is why we try to control the downward motion of the rear with bars, cal tracks etc to keep the drive shaft angle to the pinion angle in a near perfect line even under 2500 hp applications like David Wolf just done with a stock suspension Mustang to lay down a 4.44 in the 1/8.

You have to remember some side walls are very soft, some are stiff, some people let the rear just do what it wants. We saw a video of a drive shaft under power on a drag car that was @ 0 pinion angle. NO IT WAS NOT 0 PINION ANGLE TO THE GROUND, THE GROUND HAS NOTHING TO DO WITH PINION ANGLE EXCEPT FOR THE GROUND IS UNDER THE PINION! You are measuring the difference between the two to make a straight as possible line when power is applied.

A chassis that moves a ton in a downward motion will cause the front of the pinion to move upward. If you do not think so then why do the make a thing called a slapper bar? A bolt on slapper bar is just something to keep the torque of the engine going threw the drive line in check with the leak spring which will bow right up on a decent launch as much as 10° with no bar and chunk the drive shaft right out. Seen it many times from wheel hopping and people thinking a stock leak spring don't twist!

Keeping the leak spring in check by bolting the bar under the center of the rear, then placing the end of the bar on the eyelet of the leak spring, which is solid, then taking the adjustable J bolts and giving or taking away preload is how we got stock leaf springs to work in a drag racing application. J bolts were killer!

Now I know some people don't think things threw, but to say pinion angle is something that does not matter or you don't have to measure the difference between the drive shaft and actual pinion angle is silly. With all chassis and types of, you have to account for pinion angle correctly. The rule of thumb is ladder bar type up to 4° negative and hopefully when the hit happens and the car is moved out, you don't go over center. Even when we let off the power at the end, we had to have devices that did not let the rear come to far down. This could do the same thing. It would cause a severe negative angle and cause the rear to wine like a mother and sometimes roll the universal joint over so far, the drive shaft pinched and caused it to break and come out.

4 link cars usually 2° is fine, but it all still comes down to downward travel opposed to the lock front position of the drive shaft. Which we all know does not move. Do not under any circumstances tune a chassis like any of these and not think pinion angle does not play a huge part in power getting to the ground and power being eaten up before it even gets to the rear!

[Awesome Bill]

I think we will agree that you should always set the car up, regardless of what you are doing, on level flat ground. Doing it on an incline or decline would be pointless when trying to adjust anything with the suspension, no? With that said, while the car is on level ground, if you measure just the pinion, use a starting point, depending on the suspenion type, and work from there after each pass, you will find where it wants to be, regardless of any other angle. If you measure the shaft angle and add, multiply or subtract what the pinion angle is, you come up with a false reading. You can come up with -1 when the pinion is really at -4. Doing it the way I have done for years, just knowing what the actual pinion is, you will not get a false reading, and you know it won't go into positive numbers. No racetrack has a starting line that is going uphill or downhill, so you know what it will be at. If you start, lets say at an actual -4 and adjust a degree each pass, you will see a difference in how the car runs, and you will get to a point where it will slow down. You then back off to where it ran the best and your set. Same holds true for adjusting bars and instant center. I think by taking into account other angles just gets confusing. I have seen guys so it by measureing other angles and the pinion winds up going positive even though after their math it says the pinnion is negative whatever...For example, doing it off the shaft, let's say it is at a -5, and the pinion is -4, that would mean you have -1 pinion angle??, when in reality it is -4. Now if you are aiming for -4 pinion angle that would mean you would have to move the pinion way out of whack to achive that -4 when in reality it will be like -9 at the pinion, which is way off...Pinion angle is just that, angle of the pinion and that is all that should be measured. Again, I am not telling you or anyone what to do, just a cool friendly debate..:D I am just stating what works for me and has worked over the years and when I come across guys that have done it the way you are saying, the cars run much faster..Hope I didn't confuse you much?

WOW, the pinion angle to the ground is one #, and one you do not even have to use and has no bearing on pinion to drive shaft angles. Pinion angle has never been or will never be used in relationship to the ground or any flat surface. You could use the ground as the base once real pinion angle is achieved as a start and stop point if you would want to. I have seen this. But the baseline has to be done first.

You do not even need level ground to measure this angle. All the car has to be is sitting on all 4 wheels. The ground has nothing to do with it. If the pinion angle is climbing the chassis, like all drive shafts normally do in stock applications, the is an angle. The Pinion is normally at another angle and that is why we need a universal joint to attach the drive shaft to the pinion.

If the pinion angle is sitting @ 4° downward on a car sitting perfectly still, the angle of the drive shaft going up hill will be another angle. What ever that angle is, you have to add mabye, if someone really messed up, but usually subtract that number. That is actual pinion angle. All drive trains in drag racing with a non locked differential has to have negative angle. Even a 4 link dragster has to have some angle downward to make up for chassis flex, as much as 2° and requires a drive shaft, not a coupler. Solid dragsters have a coupler and I would still bet some pinching goes on in our Top Dragster stuff with the tall gear, big tires and tons of torque.

The drive shaft and pinion are not constant. The angle will change from normal take off to a hard launch. As far as changing the pinion angle, it is not an easy thing to do on the ground let alone even on a lift!. A four link car requires you to remove 1 bar to just set the pinion angle and then you will need to re preload the other bar so the car goes straight when you apply power.

With ladder bars, if you just screw the double adjustable bar to put more pinion angle in on 1 bar, you unload your preload. Those things have to be set with just 1 ladder bar hooked up and yes it matters which one.

With stock suspension stuff you have to add shims or take away shims. With some types of cal tracs, they are adjustable but you are then again taking away from one to achieve another.

Get your chassis book, turn to pinion angle and they all say the same. Drive shaft minus or plug pinion angle gives you exact pinion angle your chassis has.

[want-a-be]

One other thing that none of us have addressed here is the amount of forward movement you have left in the drive shaft while the pinion is trying to climb the ring gear. Due to the negative pinion angle the yoke will slip farther forward into the back of the tranny. If you don't have enough room to slide into the tranny you'll get bind and upset traction. It may also lead to broken parts. Too much the other way and when you let off the gas the yoke could slip out of the tranny. Seen both problems in the dirt track scene. Those guys have a ton of chassis movement.

Don

[BERT]

Rule of thumb is 1" of slip for trans yolk.

[want-a-be]

Nice new avitar you're sporting there Bert. You go racing last night?

Don

[BERT]

Thanks, No I wish , that was a couple weeks ago at the national open in sacramento CA. :)

[want-a-be]

Wow....looks like you have it hooking well enough. Guess I'm going to have to reread some of your old posts and see what you're running in that thing.

Jeff needs to talk to you a bit to get his chassis to be doing the same.

Don

[BERT]

I will share everthing I've done with jeff. The car is hooking well on a 9" tire.

[Bad Influence Racing]

Large post deleted... not pertinent to the thread at hand.
Please keep arguments to PMs or email.
Temporary ban issued.
- DV

[Awesome Bill]

Also not terribly pertinent to the thread, and insulting.
Temporary ban issued.
-DV