driveshaft and rear pinion angle

[Toms63SSQB]

Has anybody that has installed a Ford rear end on their X frame know what the drive shaft angle is from the carrier bearing to the rear end U joint? I have a 3 inch IEDS and the angle on the ds is 8.4 degees down and the rear end yoke is 1.0 degree up. These numbers were obtained with all 4 wheels on the concrete floor in my barn. I have UMI adjustable upper control arms so an adjustment won't be too difficult. These numbers added together give me a total of 7.4 degrees. I noticed from an earlier post that Steve from "Wully Bully" adds the two together and calls it the total angle. I believe he said he running 7 degrees. so I'm thinking what's good for steve is good for Tom.

 

[Kdurgin]

So what angle are you running through your rear u-joint?

 

[DaveFoster]

I'm not an expert, but I do know that more down angle gives added forward bite, but at a coast of wheel hop on deceleration, oval track pavement cars run 6 or 7 degrees down, dirt guys run more, sometimes as much as 15 depending on their driving style. I would listen to the experts if they will share.

 

[Kdurgin]

I'm not an expert, but I do know that more down angle gives added forward bite, but at a coast of wheel hop on deceleration, oval track pavement cars run 6 or 7 degrees down, dirt guys run more, sometimes as much as 15 depending on their driving style. I would listen to the experts if they will share.

What about the excessive angle through the joint itself?

 

[DaveFoster]

Again, I'm not an expert, but pinion down angle noticably improves forward bite, at the expence of robbing horsepower at the U joint angle. Guys with money and Dyno's have the answers, but my pavement oval track racer goes faster with about 7 degrees down, one of my fellow racers tried less angle, about 2 or 3 degrees down and freed up some power but lost forward bite, he also quickly fried his rear tires and after several laps of getting looser and looser, he spun out all by hisself, he couldn't get his rear angle increased fast enough. But he is studying and reading books for future adjustments or test sessions. Remember some classes require stock or stock appearing parts. I run stock rear arms with urathane lower bushings and rubber upper bushings, I felt that the upper would flex and increase down angle on acceleration, and decrease angle on decelleration. I have no data to prove or disprove my simple theory other than my competitors are wondering why old fart Dave is running with the leaders now. There is a lot to learn about rear geometry, and that info is hard to come by. The guys who know it are easy to spot, they be quick off the line.

 

[Kdurgin]

I raced circle track cars 13 years, on clay for 6, and asphalt 9, in street stock, late models and Pro stocks. I never ran more than 3 down on the pinion personally. I'm not concerned about bite or u-joint wear so much as vibration?

 

[Toms63SSQB]

OK then, I am now at 8.4 down on the driveshaft and 1.0 up on the rear pinion, I would have to be 4.4 degrees up on the rear pinion to get the 4 degrees your talking about at the u Joint That doesn't seem right that I would be starting with the rear end up 4 degrees at the start or is that just how the math works out. No that's not right because as I raised the rear pinion the ds would be coming up also. I guess what I'm going to do is go out there today and do some adjusting on the upper arms and see where it actually comes out.

 

[jwhotrod]

Driveshaft

I too will say i am not an expert, but I would suggest you pose this question to Greg Frick at Inland Empire he is an expert and will help you. What I do know is that racing conditions and street "cruizin" conditions are completely different.

The general rule is the down angle on the driveline and the up angle on the pinion in a "perfect" world should be equal and opposite to cancel out ech other and not vibrate. Cyclical Harmonics. I know what you are saying about down angle for track traction, etc. but it also depends on your suspension type. coils or leafs, 4 bar or other. Talk to Greg frick he will help you, also there is a huge amount of info on IEDS web site.

good luck.

Big jim

 

[Tic's60]

It's all in relationship to the driveshaft, pinion angle should be down at least 4 dgs from driveshaft with a stock street 58-64 suspension. With some aftermarket setups with solid mounts you could run with less. Idea is, under hard acceleration pinnion angle comes to zero dgs. good for drag racing, can't say for a roundy round car. Just my opinion.

One of the other factors is the type of bushing you use. Older stock rubber ones, poly or solid HEIM joints. The less flex you have the less degree's you need to go. I run solid HEIM's at 3 down.

 

[Toms63SSQB]

I just got off the phone with Inland Empire and they say adjust the rear pinion to the driveshaft at 3-4 degrees total. I'm heading to the barn to make that adjustment. Thank you ALL for the great response and assistance.

 

[Kdurgin]

I just got off the phone with Inland Empire and they say adjust the rear pinion to the driveshaft at 3-4 degrees total. I'm heading to the barn to make that adjustment. Thank you ALL for the great response and assistance.

Can you elaborate on adjusting the pinion " To the driveshaft at 3-4 total" ??? I am assuming to the rear shaft? I was told to set my pinion to the FRONT shaft angle the same amount, in my case 1.8 degrees up.

 

[Toms63SSQB]

As I understand what IE said was that you set the rear driveshaft and pinion angle to 3-4 degrees total, The total actually being a minus degree number. That means you add the down angle from the driveshaft and the up angle on the pinion to get those numbers. remember the DS is a negative number and the pinion is going to be a positive number. subtract the pinion from the DS angle and you get total angle, DS to pinion. IE did not mention anything about the front of the DS, I do have a 2 pc. driveshaft w/ a carrier bearing. I am thinking correctly, right? I also have a Ford rear end which I think sets the pinion lower than a cheverolet.

 

[Toms63SSQB]

This afternoon I went out to the barn and adjusted the pinion angle up to 2.4 degrees and the DS is down to 6.4 Degrees with a total pinion to DS angle of exactly 4 degrees. I locked the adjusting nuts on the upper control arms and now I'm going to wait til spring to see if this is going to work.

 

[Kdurgin]

Is the rear of your rear shaft higher or lower than the front of the rear shaft?

 

[Kdurgin]

Front driveshaft has no bearing on pinion angle.

I know it does not change or affect the angle of the pinion. I am saying it may induce an annoying vibration. 1/4 mile at a time on the hammer maybe not, but I am talking about steady highway speeds like 60-80 MPH. Have you heard of that? Thanks.

 

[1961BelAir427]

Everything I have ever read or heard says that you want the pinion angle to be 0 under power, and negative at rest.....the 3, 4, or whatever you decide to shoot for needs to be NEGATIVE pinion angle.....meaning the pinion points DOWN towards the ground X number of degrees. You want this because it is going to rotate UP under power. I think if you have a pinion angled upwards to start with that you are very likely to start breaking parts if you put any power to it.
Am I alone on this thought?

 

[DIV1RACER-2]

Tom,

From the pictures you posted a while back it looks as though the car is not entirely complete. All the weight needs to be in the car , as that effects ride height & the pinion angle.

If you have a 2 peice driveshaft , the center support is mounted to the frame closer to rear end than just being into the back of the trans. That makes the shaft shorter and it is effected more with than a longer driveshaft. By lowering or raising the ride height it will also change the rear axle attachment link lenghts & move the pinion up or down.

Pinion angle should be nearly 0 or - a degree down under acceleration, as someone else mentioned that the harder the attachment points are [ heim v/s rubber ] also must be factored in. The pinion will be a - number & the driveshaft will be +.
8 degrees driveshaft - 4 degrees down on the pinion will give you an actual angle of 4 degrees.

Your car looks great an hopefully we'll get to line up at this years gathering if we can get together !!!!!!!!!

 

[jim_ss409]

I'm certainly no expert on drivelines but I do know one thing that's helped me to understand the most common source for driveline vibrations.
Here's the thing... If you were to put a degree wheel like you'd use for degreeing a cam on the output shaft of the tranny and another degree wheel on the driveshaft you would find they would only read the same at two places per revolution. The working angle of the U joint causes the driveshaft to go faster then slower than the transmission twice every revolution. The greater the working angle is the greater this effect will be.
So, if you've got a 5 degree angle at the front U joint you're probably going to feel a vibration unless you do something to correct it. All you have to do to correct it is use the same 5 degree angle at the rear U joint. That way the output shaft of the transmission and the pinion of the differential will be spinning at exactly the same speed through all 360 degrees of each rotation.
For a single driveshaft the pinion and the transmission output shaft should be parallel to each other but as others have said the suspension will wind up under acceleration so it's usually best to aim the pinion down a bit to compensate. How much lower you go depends on your suspension and how you use the car. For a drag car you probably want the driveline angles to be perfect under hard acceleration but for a cruiser you probably want the angles perfect at light load and let them be off a little under full load and braking. The angles won't be perfect under all conditions, and they don't have to be, as long as they're close you won't feel any vibration. My guess is that aiming the pinion down about 2 degrees less than parallel to the transmission output shaft would be about right for a street driven car with leaf springs and maybe as little as 1 degree for our X frame cars with the three link suspension. For a drag car you'd probably want to point the pinion down an extra degree or two.
When it comes to the two piece driveshafts like we have in our cars, I don't really know how to compensate for the angle at the center U joint. I don't know how hard it would be to figure out, but I don't know how it's done.
I don't have a manual here but if I remember correctly our cars don't use the regular parallel method of U joint angle cancellation. I think they use the less common "broken back" method. The second driveshaft in the picture below shows the broken back method, it looks weird but it works.

 

[Toms63SSQB]

I am getting confused. but first to answer some questions, Kdurgin, the front of the rear driveshaft is higher than the rear at the u-joint connection. 1961Belair427 my rear pinion is definitely heading up, if I set it at 2 degrees down and added the driveshaft down angle which would be close to 10 degrees down that gives me a total of 12 degrees? Am I missing something here or am I just confused or both, I thought to figure the Driveshaft to pinion angle you take both Driveshaft angle and pinion angle and added them together. Denny your right I did the adjustments yesterday and the front bumper had been installed but no hood or interior or my weight either. Does the rear pinion heading up really make a difference as when I would launch it would come up to about zero. If anybody wants to call me and try to explain this to me I would welcome your call sometimes talking about it works better. 440-774-2326 or my cell is 440-935-5099:?:?:?

 

[Tic's60]

I remeber a thread about that last year. Was a good read! My driveline shop I use also mentioned the same thing when I had my assembly spun balanced. Was only 40.00 and worth it to have the entire assembly balanced. They actualy setup the driveline with the carrier bearing pinion angles everything then spin the assembly to some crazy numbers, 10,000 RPM??, and balance it.
Pretty neat to watch!
From a distance!!

I'm certainly no expert on drivelines but I do know one thing that's helped me to understand the most common source for driveline vibrations.
Here's the thing... If you were to put a degree wheel like you'd use for degreeing a cam on the output shaft of the tranny and another degree wheel on the driveshaft you would find they would only read the same at two places per revolution. The working angle of the U joint causes the driveshaft to go faster then slower than the transmission twice every revolution. The greater the working angle is the greater this effect will be.
So, if you've got a 5 degree angle at the front U joint you're probably going to feel a vibration unless you do something to correct it. All you have to do to correct it is use the same 5 degree angle at the rear U joint. That way the output shaft of the transmission and the pinion of the differential will be spinning at exactly the same speed through all 360 degrees of each rotation.
For a single driveshaft the pinion and the transmission output shaft should be parallel to each other but as others have said the suspension will wind up under acceleration so it's usually best to aim the pinion down a bit to compensate. How much lower you go depends on your suspension and how you use the car. For a drag car you probably want the driveline angles to be perfect under hard acceleration but for a cruiser you probably want the angles perfect at light load and let them be off a little under full load and braking. The angles won't be perfect under all conditions, and they don't have to be, as long as they're close you won't feel any vibration. My guess is that aiming the pinion down about 2 degrees less than parallel to the transmission output shaft would be about right for a street driven car with leaf springs and maybe as little as 1 degree for our X frame cars with the three link suspension. For a drag car you'd probably want to point the pinion down an extra degree or two.
When it comes to the two piece driveshafts like we have in our cars, I don't really know how to compensate for the angle at the center U joint. I don't know how hard it would be to figure out, but I don't know how it's done.
I don't have a manual here but if I remember correctly our cars don't use the regular parallel method of U joint angle cancellation. I think they use the less common "broken back" method. The second driveshaft in the picture below shows the broken back method, it looks weird but it works.