Well here is my issue: I have a jegster non-adj. torque arm. I was wondering if anyone here has successfully modified any given part of this torque arm setup to get a -3ish pinion angle?

Any ideas or experiences are welcome but please keep it related.

 

To keep the u-joints happy, the pinion should be at the same angle as the crankshaft. You can aim it down a couple of degrees from there. Ignore the driveshaft completely.

When properly set up, the crankshaft/tranny yoke should be pointed right at the yoke on the diff. That doesn't mean the driveshaft will be level with the ground.

With a non adjustable torque arm, you're really limited to what you can do. Sell the torque arm and buy an adjustable one.

 

As the car sits right now the pinion angle is about negative 2 and would like to have -2.5 or 3. I didn't think the non-adj arm would leave me many options.

thanks for the info

 

[quote=AlkyIROC;4610109]To keep the u-joints happy, the pinion should be at the same angle as the crankshaft. You can aim it down a couple of degrees from there. Ignore the driveshaft completely.

When properly set up, the crankshaft/tranny yoke should be pointed right at the yoke on the diff. That doesn't mean the driveshaft will be level with the ground.


Just wondering how you check your pinion angle? I have always made the pinion 2.5-3 degrees negative from the drive shaft angle. Because the pinion rotates up under load and in theory it should become in line with the driveshaft. Let me know if that doesn't sound right.

 

[quote=superT;4610151]using an angle finder on the driveshaft record the measurement
then place it on the pinion take that measurement, the pinon angle is the combination of the two
try not to go over six deg total

2 + 4 = 6 any combo of the 2
even 0 + 6 = 6 (with a auto trans)

this is the short and sweet side of it
when your standing on it they line up under power/TQ
This is the Drag Race side of things

when at the start and the TQ hits the third member and stands it up to be inline with the rest of the parts.(Under Power)
the more angl= the less of a Hit to the drive train.. (like if you have a slipry lane t the drag strip. and want less of a Hit)
add a bit of pinon angle.

now just driving on the street getting a bag of CHIPS.. THATS not going to be the same

 

pinion and tailshaft angle should be equal but opposite, so x deg down & x deg up. Measure @ ride height, driveshaft angle itself is not important, just take angle measurement on tailshaft vs driveshaft and then driveshaft vs pinion and get actual driveshaft to pinion & tailshaft angle. This to eliminate any angle influence of car rake.

 

http://www.youtube.com/watch?v=UAQgLbhQ0uk

This is a link that BMR made for adjusting the pinion angle

 

BMR is assuming the tailshaft yoke is pointed at the diff yoke. As soon as you put taller tires on the car or change the tranny mount which could raise or lower the tailshaft yoke.

The above picture shows the diff yoke pointed upward from the driveshaft. You could angle it down a couple of degrees and it may still be pointed upward of directly at the driveshaft. Since the pinion angle needs to be in relation to the crankshaft angle, this is fine.

Simply measuring the driveshaft and pinion angle will work in most applications, it's not the proper way of measuring the angle because it doesn't take into effect the crankshaft angle. The majority of people won't change the height or angle of the engine/tranny but when you put a taller tire on the car, it will raise the diff higher in relation to the tranny yoke unless the ride height is dropped back down. This will change all the angles and to keep the u-joints happy, the pinion needs to be adjusted to the same angle as the crankshaft.

 

If the crankshaft is at 0 deg, and the pinion angle is at 0 deg you are not making the U joints happy if the diff and the output shaft of the transmission are on different planes. Lets say for example the centerline of the rear u joint is 6 inches lower than the front u joint centerline, and lets say for example the two centerlines are 6" away from eachother (just an example) you are going to have a 45 degree angle on your U joints.
Now you angle up the pinion angle so that the driveshaft angle and pinion angle match, you have eliminated any deflection on the rear U joint (actually you always want a slight angle) and now you only have a 45 deg angle on the front U joint. In practice however, the axis of rotation isn't the u joint, it's the rear axle (well not quite true, the centerline should be about the lower LCA bolts) so, when you angle up the pinion in this example, you are also raising the centerline of the rear U joint thus reducing the deflection on the front U joint and at the same time reducing the actual amount of angle you need to change the pinion angle to make it match the driveshaft.

Tires have nothing to do with your pinion angles, taller tires or smaller tires do not change the drive train angles relative to each other. A taller tranny mount will however.

The only reason to put in some negative angle relative to the driveshaft is so that under hard acceleration, the angles move to zero. You are compensating for the rear axle rotating slightly due to deflection in bushings, mounts, etc

 

Pablo
nailed it a bit more..



will have to upload the Under car Video of the car on take off, you will see how the pinon angle stands up, from street driving angle, to Line up, on take off.

and yes with more HP and TQ you will have to set a bit more angle to yours, (tuning)
drag race/road race are diff and so are the angles for ea car.

let me refresh, in a Nut shell
Pinion angle effects the effciency of power transmission from the driveshaft to the rearend, the pinon angle is the spread between the Pinion centerline and the Driveshaft centerline. for Maximum Performance, the Ideal is to have a slight pinion Down Angle (min.2 degrees) under full Power. Obviously, the pinion angle changes as power is applied and the axle housing begins to twist as the pinion tries to drive the ring gear. rear axle wind-up can take some of the inital energy or "Hit" away from the Launch.

"so easy, a cave man could do it"

 

Wow, I really needed this thread. I just bought a UMI trans mounted adjustable torque arm. (These new TQ arms are freaking heavy!!!) and I was wondering on how to do the adjusting. So in layman's terms I want to set the angle of the pinion to match the angle of the crankshaft? Whats the easiest way to do this? I'm a newb when it comes to suspension tuning.

 

No. I don't know who came up with that nonsense but that is definitely NOT what you want to do.
Re-read my post. The whole point of adjusting pinion angle is to make u-joints live. So you ideally want the angle of the U joints at zero or close to zero. The only reason to angle the the pinion angle down is to account for the axle rotating upward on hard acceleration.

Like I said, re read my post and let it sink in. Think of your u joints as U joints on each end of an 3/8ths drive ratchet extension. Your pinion angle is the angle of the socket on the end, and the ratchet end is your transmission. Lets say the ratchet is at a fixed height an inch higher than your socket. Now you are moving the angle of the socket relative to the extension. Which angle on that socket is going to produce the least sharp turn on that last U joint? Its not going to be the same angle as the ratchet axis I'll tell you that much.


EDIT: There is a vibration issue I did not consider. See post 14 and 16.

 

look, these numbers are just examples. The angle of the Driveshaft is exaggerated. The point is, if the crank and the rear diff are on different planes and you set them to the same angle, that does not reduce the angles on the U joint to the best angle or even an acceptable angle.

Since these angles are exaggerated I want you to ignore other considerations like shock mounts and the like.
Axis is the axis of rotation. Since it is further back from the centerline of the U joint it is also going to raise the driveshaft slightly. 5 degrees in my example is probably an exaggeration, but its for illustration purposes only.

As you can see, setting the rear pinion angle relative to the crankshaft makes no sense. Furthermore, your tires have nothing to do with it.


EDIT: The example is not considering a vibration issue introduced by having joints at different angles. See post 14 and 16.

 

http://www.carcraft.com/howto/91758/index.html

http://www.ls1tech.com/forums/gears-...tion-help.html

http://www.hurst-drivelines.com/file...roc_111606.pdf

http://www.vibratesoftware.com/html_...aft_Angles.htm

http://www.superchevy.com/technical/...ing/index.html

 

Well I must say that, I think I asked the right question:-)

Anyhow, I am going to check the angles from the tailshaft and pinion and do the math to see where I'm at. Thanks guys!

 

Ok I read these links. You got me good
I didn't have the whole picture.

I have not seen the vibration issue explained or addressed before.
It does however make sense. I was under the mistaken impression that working angle of the joints was the only consideration. It is however painfully obvious now that different working angles introduce different amplitudes of imbalance on opposite ends of the shaft because of the different speeds that they are changing directions. Hence they don't cancel out, introducing harmonics as opposed to waves in equal and opposite directions.

Teachable moment here, brush up on your data before thinking you've thought of all the factors with just your little brain and end up doing what I just did

I will stand behind my statement that tires make no difference though.

Eating crow now.

 

That's why I originally said to ignore the driveshaft when setting the pinion angle however on most street cars, the tranny yoke and diff yoke are close enough in height that just adjusting the pinion angle in relation to the driveshaft can be close enough but not all vehicles are the same. When adjusting the pinion to a few degrees down angle, it's in relation to the engine/tranny angle. The pinion may still be pointed upward in relation to the driveshaft.

With any driveline or suspension changes, these angles can be a lot different than stock. Lowering the car changes the ride height which means the angles change. Pinion height stays the same but tranny yoke is lower.

For me, my engine and tranny are lower than stock while the 32" tall slicks position the diff pinion higher than normal because the body ride height is only slightly higher than normal at the rear. This means my driveshaft goes up from the tranny to the diff. If I angled the pinion down to be inline with the driveshaft, it would screw up the working angles. At 145 mph through the traps, I have no vibrations that I can feel.

If you took off the stock 26" tall tires and put on 28" tall tires without changing the ride height, the pinion will sit slightly higher than stock. Since the ride height didn't change, the taller tire also moves the body slightly higher but only at the rear. The tranny yoke may only move up half the distance but it's still enough to change the driveline angles. Installing 28" tall tires and lowering the car will change the height difference even more.

This winter I'm cutting out the tranny tunnel, repositioning the mid plate higher and going to try my best to aim the tranny shaft at the pinion yoke to reduce the working angles. Header collectors hitting under the floorboards is my limits. Right now clearances are perfect but I don't like the working angles.

 

I work on heavy trucks. Most trucks now have air bag suspension. If the air ride height isn't set properly, the trucks will experience a noticeable driveline vibration because the ride height changes all the driveline angles.

 

I still fail to see how changing just tire diameter changes the angles in relation to eachother. You are just rotating the whole drivetrain about an arc with the front spindle as the axis. Maybe I am not understanding you, but just the change in tire size does not move the rear pinion in relation to any other part in the drivetrain.

 

You guys (Alky and Pablo) are a good reason I like this forum. I mean, if somebody post a problem or question it usually gets answered. Someone on this site has either had the problem or someone else just knows the answer. Just thought I would express that thought.

 

I answer many questions if I can but there's also a lot of questions I'd like to answer but won't because it gets too technical and the person asking the question doesn't appear to have enough common knowledge to perform the task.

I'd rather not answer the question than risk having the person cause even more problems or worse.

 

I can understand that man. Sometimes its just best to let them go through the whole trial and error thing. Then maybe the next time they will have more understanding skills.

 

thanks for this thread. Used it to set my pinion angle and I certainly notice a difference. In reverse (5spd) at slow speed you'd almost feel the diff or u-joints providing some resistance and its smooth as silk now. Both my tailshaft and my pinion were pointing up prior to setting it correctly. Tailshaft is -2.5 and diff was -1.5. Set the diff to +2.5 and I believe i'm good. The car is lowered and I have the adjustable spohn torque arm that is mounted to their crossmember...so one of these parts threw me out from where it should have been. All is good now. Thanks!

 

Well I got my torque arm in and it's awesome, the car feels completely different but I have one question. How do you read the angle finder? lol I know newb question but I've never used one before. From what I'm guessing the finder says I'm -4 degrees I'm not to sure.

 

The angle is always in relation to the front. If the angle finder says the back is lower than the front then it's a negative angle. If the back is higher than the front then it's a positive angle.

If the tranny is pointed down at the back 3* and the diff pinion is pointed up 3*, the 2 angles cancel themselves out and you have 0* working angle. Lowering the pinion angle so that the pinion is pointing up only 2* means it has a 1* down working pinion angle in relation to the transmission angle.

 

Ok just for clarity if the pinion is pointing down it's positive and if it pointing up it's negative? cause if so I believe i'm actually after checking again 5 degrees positive at the pinion because it's pointing slightly down. I haven't been able to check where the trans angle is at.

 

don't get too caught up with the positive and negative readings on the angle finder, and think more about the angles in relation to EACH OTHER. Remember, angles are all measured in degrees, so how could there be a negative angle unless your relating it to another angle? Think of plus and minus, not negative and positive. Reading the angle finder from the driver side might show a +2, and it'll then read a -2 from the passenger side, but of course, nothing actually changed.

That being said, I wanted to point out how great this thread is. SO much misinformation on the web about this topic. I too had always measured the rear end pinion to driveshaft angle. And quite frankly, even though I know better, that STILL makes sense!!!!! ...but, it's wrong, as has been shown. Crankshaft and rear pinion are the way to go.

HOWEVER.....one thought that I have is, once you've gone ahead and measured your angles properly, set any negative angle on the rear that you want, and buttoned everything back up, you STILL have the physics of the U joints to worry about. Should you not measure the rear pinion to drive shaft angle, and crankshaft/output shaft to driveshaft angle to make sure you're not at too drastic of an angle for the U joints to operate properly? Presumable on a new car they'd be fine, but these older cars could be all outta whack, and there's no telling what mounts don't line up straight anymore. No one ever mentions this. Just food for thought.

 

well I have developed quite the vibration going down the road and I was able to get some measurements tonight and here's what I came up with, all these measurements are from looking at the gauge from the driver side of the car.

front to back
-4 balancer
-2 tailshaft
0 Driveshaft
2+ pinion.

How should I adjust this to try to get rid of the vibration? It feels like it's beating the hell out of my u joints.

 

How can your balancer be different than the tailshaft? They should be on the same plane?

If your tailshaft is -2 and the pinion is +2 then the pinion working angle is zero however you could angle the pinion down a couple of degrees. You want that perfect pinion angle while the driveline is under load. The diff will rotate up on acceleration.

How do you know the vibration is driveline angle related? The driveshaft could be out of balance, the tires might be bad, etc. You probably won't notice a driveline angle vibration unless the angles are great and you're at highway speeds. Your angles are close enough that you shouldn't be getting a vibration.

 

good info

 

This thread rocks! Just installed a UMI adj. setup, used this thread and made things easy, Thx Guys....

 

I just redid a truck driveline this week. The truck was almost new and a conversion company installed a tank on the back but a pump mounted under the tank sat right where the second hanger bearing was.

The truck uses a 3 piece driveshaft with 2 hanger bearings. There's a slip yoke in the last section to allow the diff to move up and down. The conversion company screwed up. To solve their pump location problem, the swapped the middle and rear shaft around and relocated the crossmember holding the hanger bearing.

Ever since the customer took possession, they complained about a vibration. The boss wanted me to check for bad u-joints and that's when I noticed the rear shaft was solid and the middle shaft between the 2 hanger bearings had the slip yoke which did nothing.

We sent both shafts out to the driveline shop to be refabricated. Once installed, I started checking driveline angles.

With the real short rear shaft, the working angle to the diff was close to 8* and there was no way I could change the diff pinion angle so I started working with the driveshafts.

Using the trucks frame as a zero reference point, the first driveshaft was angled down from the transmission. The second driveshaft was almost parallel to the frame so technically it was angled up at the back in relation to the front driveshaft. The third driveshaft then had a steep angle to the diff.

After doing a bunch of measurements, my best course of action was to relocate the second hanger bearing down 1-3/8". This didn't change anything with the front driveshaft. The second driveshaft now had a downward angle slightly more that the first. The u-joint at the first hanger bearing now had a working angle of -0.6*. Installing the third driveshaft, the last 2 u-joint angles could be checked. The working angle at the second hanger bearing u-joint was -0.3* and the working angle at the diff was now close to 4*.

The working angles were as minimal as I could get them. I didn't want any zero angles as that can eventually cause brinelling in the u-joint. The truck was taken on a test drive and there were no more vibrations. That was mainly because the third driveshaft that attached to the diff now had a slip yoke in it. Correcting all the other driveline angles just made all the u-joints happy.

In a car with only a single driveshaft and the slip yoke that simply slides in and out of the transmission, the theory is all the same. When setting the pinion angle, don't assume that just because the pinion is pointing upward at the front that it doesn't have a negative angle.

I could have lowered the front hanger bearing down slightly which would have allowed me to lower the second hanger bearing more. That would have made the driveline angles a little straighter as they came off the transmission and would have reduced the working angle at the diff even more.

 

.

 

Does the below procedure seems right ?? Just wondering because I will be installing a new TA soon. This method is essentially saying you dont even need to measure anything on the driveshaft correct? Just put the angle finder on the rear and and the harmonic balancer and as simple as that?


Follow this procedure.
First go to Sears and buy the $25.00 magnetic digital angle finder that reads to the .1 of a degree. The one with the rotating needle is ****.
1. Put the front wheels on ramps or the front chassis on jackstands.
2. Put jackstands under the rear axle tubes.
3. Make sure the entire car is supported well and mostly level to the ground.
4. Place the angle finder (AF) on the front VERTICAL face of the harmonic balancer. Record the reading.
5. Place the AF on a VERTICAL surface on the rear end.
6. While adjusting the torque arm, set the AF to the exact same reading recorded in step 4. The crankshaft/tranny and pinion should now be perfectly parallel.
7. With the AF still on the rear end, again note the reading. Adjust the torque arm so the pinion yoke slowly rotates down toward the ground. You want to lower it 2 degrees compared to your original reading.
8. Tighten down the torque arm.
9. Drop it and dive it. You now have dead nuts on negative 2 degree pinion angle.

If the vibrations are still there, the drive shaft is out of balance. I have been down this road. I feel your pain. Follow these directions and wrap this bitch up.

 

Sounds perfect.

Taking the engine/tranny angle may be different in different locations. Another option is to get the angle from the engine oil pan rail. If the pan is on, this may be difficult. Off the damper should work as long as you're only on the part that is part of the crank. If the outer ring is wider, it may give a false reading if the rubber isolator has moved.

The best location for the diff is off the pinion yoke itself. With the driveshaft removed, Place the angle finder across the yoke and +/- 90* to get the horizontal angle.

Another way of looking at the angles and it's easy with a digital angle finder. Place the angle finder on the engine/tranny angle and zero the angle finder. This is now the plane you are shooting for. Placing the angle finder on the diff, you can see exactly how many degrees up or down the diff is in relation to the engine/tranny without having to do math.

I did 2 more trucks at work last week. Sister trucks and both had highway speed vibrations. The yoke of the diff was pointing down in relation to the tranny. Being able to actually adjust the pinion angle on this type of truck suspension and bringing the angle closer to parallel with the engine/tranny removed the vibration.

I have some software that's part of the Allison transmission software that allows me to punch in all kinds of driveline angles for the multiple u-joint drivelines. With those angled down pinions, the software spit out lots of problems. With the new pinion angle, the software said everything was happy. No more guesswork.

I've never tried to put the race car's driveline angles into the software. I don't think I want to see the results.

One last thing you can do after adjusting the torque arm. You know the vertical angle of the diff yoke. +/- 90* to get a horizontal angle then install the driveshaft and get that angle. You should be able to calculate the working angle of the diff u-joint. The angle should be small but not zero.

 

book marked for future referance.
Thanks for the info.
Kory

 

Still confused on this!

My trans is pointed down 2.5 degrees
The diff is currently pointed 1 degree up
I have an adjustable torque arm.

So do I need to have the diff pointed down 4 degrees to have a -2 angle??

 

Start with the pinion and the transmission AT THE SAME ANGLE TO THE GROUND; another word for that is PARALLEL; then adjust the pinion a degree or 2 DOWNWARD from there. That way, when the stress on the U-joints is at its max during hard acceleration, and the rear rotates UPWARD due to the torque on the wheels, it will put the U-joints more nearly into the PERFECT state, which is, with the pinion and the trans mainshaft PARALLEL (SAME ANGLE TO THE GROUND).

This is not rocket surgery here. It's just a car. Don't outsmart yourself over something so simple and obvious. PARALLEL. Imagine extending a straight line through the 2 shafts, and make those lines PARALLEL, and tweeeeek from there. It's just not that hard.

 

So thanks for that.
I have a custom made trans crossmember, and a 9", so nothing is stock

So can you answer my question?
Do I need to have the diff pointed down 4 degrees to have a -2 angle??

 

You need to make the trans and the pinion PARALLEL, whatever that number happens to be; then point the pinion a degree or so downwards from there. What you're saying doesn't seem right, but that's mostly because you're not using language like PARALLEL, that would carry UNAMBIGUOUS and UNMISTAKEABLE meaning. You're asking us to fish for you instead of teaching you how to fish.

Don't outsmart yourself. It's YOUR car.

I think 2° is too much. Unless of course you have typical wore-out 35-yr-old stock rubber dust everywhere now instead of bushings.

 

Ugh!

My trans is -2.5 degrees
The diff is currently pointed 1 degree up
So do I need to have my diff at -4?
Yes or no answer please

 

Your trans and pinion should be AT THE SAME ANGLE TO THE GROUND - whatever that is - then the pinion should be pointed DOWN (closer to the ground) about 1° from there.

LOOK AT the drawing in post #6. It shows it pretty clearly.

No I am NOT going to catch the fish for you, clean it, scale it, cook it, and serve it to you, FOR YOU.

 

So according to what you are saying , it is almost perfect now
I should have -1.5 (I'm aiming for 2*)

I'm glad for your partial help.

It would help to give definitive answers, not just repeating yourself

 

It would help if you DREW IT OUT somewhat in the format of post #6 (doesn't have to be all color and show the carb and such as that) and began to UNDERSTAND that you want the trans shaft and the pinion to be PARALLEL, which is to say AT THE SAME ANGLE TO THE GROUND, and then adjusted the pinion about a degree lower toward the ground.

Put forth a little mental effort. UNDERSTAND. Not, DEMAND a handout. Yeah I know this is 2019 America; yeah I know we have alternate winners and participation trophies that are the same for the losers as they are for the winners; yeah I know some high schools have abolished valedictorians (don't ask) because of the "mental anguish" that … LOSING … inflicts on … someone …; but, I will NOT do your work FOR YOU.

 

Thanks!

You sure expend a lot of negative energy when a simple answer would have helped the situation 4 posts ago