Please Help me set my Pinion Angle... again

here is where I'm at...

I got the 10 bolt rear end squared, front to back and side to side. I jacked it up to "drive hight" cause I'm using airbags. I set the chassis at the angle i plan to drive it, higher on the rear lower on the front.

ok, now for my angles...

trans, measured at the yoke is 5 degrees (nose pointing down)
driveshaft, measures at the tube 5 degrees (pointing up towards the rear)
rear diff, what should i set it at???

i did this drawing on CAD to help illustrate. Please note that the trans output shaft is lower than the rear diff output shaft at "drive hight":



this is the rear suspension system on the truck (basically a 2-link w/ pan-hard bar):



thanks,
Yaril

 

It should be at 5* up, but you could probably get away with 4* if you had to if you didn't want it that high it will raise under acceleration. You always want the the f & r the same or withing 1 degree so the u-joint working angles match, the working angle on the u-joints will actually make the driveshaft speed up and slow down thru the driveshaft rotation. If one is alot differant then the other the driveshaft is going to fight itself and vibrate.

 

Driveshaft angles can be either paralell or intersecting. For paralell raise the nose of the rear. To do a intersecting angle tilt the rear nose down 4-5 degrees. The closer you are to the same at normal ride/load the better. Can you raise the trans a degree or 2?

 

john evans...

let me see if i understand what you are saying:
parallel is as 55chieftain has suggested. pointing the rear end nose up to be parallel to the trans angle.

intersecting is the opposite? i can tilt the nose down to be opposite of the trans angle?

if the second one works i would opt for that one because the drive shaft hits at the rear of the cab (a chassis structural cross member), but if i point it down i clear it fine. pointing up i can not completely lay out.

thanks.

 

did a little research...

"When the transmission output shaft centerline and axle input shaft centerline intersect midway of the driveshaft, the joint angles are equal. However, due to the change to unequal joint angles during up and down axle movement, this is a more undesirable condition than parallel centerlines. In this case, the maximum u-joint operating angle is determined by dividing length of driveshaft by ten. Example: A 30" driveshaft with intersecting angles would have a 3 degree permissible operating angle."

my driveshaft is 57" / 10 = 5.7 degree permissible operating angle. i am working with 5 degrees right now. i can tilt the motor / trans to get 4 degrees and be in a safer range of allowable angle.

huh, thats interesting.

 

correction (i think???) the intesecting angle must occur at the center of the driveshaft (correct?)?

if so this drawing shows trans angle at 5 degrees and rear end down at 15 degrees, intersecting angles at the center of the 5 degree sloped driveshaft:



some advise please...

 

From what I understand, that last drawing is the WRONG way. You want to tilt the nose of the pinion UP 5 degrees. The imaginary line coming forward from the pinion of the pinion centerline should be parallel to the line coming rearward from the angle of the crankshaft/tailshaft.

 

yes rusty bolts, you are correct for "parallel" pinion angle that is correct, but there is also "intersecting" pinion angle that i just learned about. it is not better than parallel but can be used.

it basically makes the imaginary line coming forward from the pinion of the pinion centerline intersect at the center of the driveshaft with the line coming rearward from the angle of the crankshaft/tailshaft. follow?

i am sure there are drawbacks to this method, of which i still do not know. i just did some quick research because john evans brought it to light. it is used in some applications.

 

Yeah, you might be right. I just can't remember ever seeing it done for a driveline. It might be a good way to do steering shafts when they have to snake around the engine.

I think maybe on drivelines, where the rear axle is going up and down, the parallel way makes more sense because the angles stay reasonable up and down through the whole suspension travel. The angles might get goofy if you did that intersecting way at extreme up or down travel of the rear suspension.

It seems like the parallel way might also help support the weight of the driveshaft better than the intersecting way and put less stress on the yokes at each end. Everything I've ever read for pinion angles always talks about having things the parallel way. It might be the other way works okay in certain circumstances though. Check some 4x4 sites, because those guys are always having to mess with their pinion angles after jacking the truck up to extreme heights. Also check places that sell drag racing and rear axle stuff like Chris Alston Chassisworks, Morrisson, or Currie.

 

This, I believe is what you are shooting for

 

Tyler : Your second drawing is the reight idea except both trans and pinion angles need to be equal IE. 5 degrees . The angle the shaft it's self runs is inmaterial. Parallel is desired but in the real world intersecting is sometimes required. In your case it would provide a postive benefit ,clearance. Did the same thing for the same reason on my 27 T allowed me to have a totally flat floor in the passenger area.

 

tylerdurben,
Your drawing on #6 would probably be the best way to set up your car. The guys a Dana driveline tech services call that setup "broken back".
51 merc-ct is also correct on possible setup. That is the more conventional approach, and I use it every day to advise my customers.
The biggest thing is to have your u-joint angles at each end being within one degree of each other for cancellation.

 

the pinion can go up or down the trick is like angles for the pinion and the transmission or engine angle..
Dave

 

Driveline phasing, according to Spicer:

"Spicer has developed guides for u-joint operating angles. Keep the true angles less than 3 degrees if possible. Three-degree operating angles do not produce vibrations severe enough to cause damage. Keep the angles on each end equal within one degree. When the angles at both ends are equal, they cancel out the torsional vibration that is generated at the drive end of the driveshaft. Never assemble a driveline so that both ends are exactly the same. The roller bearings in u-joints must have a half-degree difference in order to rotate.

"As you adjust the operating angle of the u-joint (by lifting the vehicle, shimming the rear axle, etc) you are also changing the elliptical path that the u-joint must travel in. The greater the operating angle, the less like a circle the path of the ellipse, and the greater the torsional vibration caused by the u-joint. It is for this reason Spicer recommends an operating angle of less then 3 degrees for a u-joint, a very conservative number.

It is possible to use the u-joint at an operating angle greater than 3 degrees, but it will likely cause unwanted driveline vibration, which will also decrease the life of the u-joint. If the vehicle is used only on the trail, and only at slow speeds then driveline vibration is not a concern. In this case you would be able to use the u-joint at the maximum angle that the u-joint will still be able to function."

 

If you drive it hard or have decent power, consider shimming the trans mount up so you can bring the pinion down below center. 5 up is not a good place to start from a drag/hi power chassis tuning standpoint. More like 3 down. Good luck

 

no power, hard driving here just cruising.

ill try and put the trans up 1 degree.

thanks, lots of good info here.

 

I agree more with this, I always do 3 and 3

 

John, I have to disagree with your comment somewhat about the angle of the shaft is inmaterial. You need to figure in the angle at the trans and rear AND driveshaft angle to figure the working angle of the u-joint.

 

my guess is that John was speaking to the issue of the driveshaft angle is not involved, IE the angle drawn in the first layout did not enter into consideration. take the drawing as a paper drawing, and turn it till the driveshaft is horizontal, then have ~5 degrees up for trans and 5 degrees up for the pinion (in the opposite nonparallel direction) was the second approach proposed.

 

This is right.

 

What you are after is the center line of the trans and pinion and what it's angle is in relation to the horizontal IE. here 5 degrees off horizontal . We need to keep that angle as near to the same as possiable on both ends. What I ment about the driveshaft angle was it will be whatever it is after the joint angles are set correctly. If I'm not mistaken with 5 degree jiont angles the actual saft angle would be 2.5 degrees from horizontal IF the chassis was dead nuts on horizontal. If the chassis has a rake THAT angle only would change ,you still would have the 5 degree jiont angle. Clear as mud??? my head hurts LOL
The important thing is no matter how you get there both joint osolate through the same angle.

 

Let me preface this by saying that what I learned about driveline phasing I learned from Dana/Spicer...I used to work for an air suspension manufacturer, and we had to engineer our parts correctly, so we went to them and got schooled...

So...to reiterate my previous post...

1. U joints NEED an operating angle, because they require a thrust load to "work" the bearings in the trunnion(s). Without this minimum angle, the bearings would, ultimately, seize. What that means is that a drive shaft that was literally in line would eventually fail, at the u-joints.

2. The math is really simple. An imaginary line coming out of the centerline of output shaft of the transmission MUST be parallel with a corresponding imaginary line coming out of the pinion centerline. The ONLY time this varies (and only by a degree) is in a drag-racing oriented leaf spring suspension, where chassis reaction will cause the front half of the spring to deflect, and "compensate". But, in a leaf spring drag racing suspension, that works because that particular suspension "requires" some sort of variable to tune the launch (think "instant center", which is a whole other discussion).

3. Whereas the imaginary lines coming out of the transmission output shaft and pinion centerlines must be parallel, they MUST be offset. According to Spicer,that offset must be a minimum of 1/2 degree and no more than 3 degrees.

4. These angular measurements are RELATIVE TO THE TRANSMISSION AND REAR AXLE. Forget how much rake is in the chassis...it ABSOLUTELY does not apply. Including rake in the equation will only confuse you. Think of it this way: Let's assume you have oriented the transmission and rear axle to arrive at optimum drive line phasing. Now, imagine that you are standing the car on it's nose...90 degrees to the ground. Does it matter?

5. Drive line angles are compound, or cumulative. What THAT means is that you must not only consider them on the horizontal plane, but the vertical plane, as well. This is a three dimensional issue. For example...a 9" Ford has (about) 2 12" of pinion offset...so, for the sake of argument, lets say that equates to 3 degrees. In this case, looking down at the driveshaft, you would have arrived at your optimum operating angle. So.......if that were the case.....you COULD, when viewed from the side, have those imaginary transmission output shaft and pion centerline directly IN line.

There ya go.

 

Yep DollaBill the pinion off set can be used as one of the angles. I'm so used to using early Ford banjos on the center line I kinda overlooked that . My Bad. I worked at several HD truck parts/service co. that build drivelines and I too went to more than one Dana/Spicer school. Sir! No Excuse Sir!!

 

When I had a drive line made for my truck, the people that made it told me that I needed at least one degree away from being exactly parallel otherwise the needle bearings wont rotate causing them to not lubricate properly, you got it if your tranny tail is pointing down 5, then your rear should be pointing up 5 or at least four.

 

What is actually IMPORTANT is that the working angles are the same under load. ONE WAY to accomplish this is to do as you say - have the trans and pinion parallel. HOWEVER that is NOT the only way. Having the trans tail "down" with the pinion also "down" the same amount will put the trans and pinion NOT PARALLEL but it will work EXACTLY the same. The reason is that the positional variance (per degree of revolution) REPEATS itself every 180 degrees. Granted the "parallel rule" is most common and is definitely the "right" way to do this - it is not the ONLY "right" answer.

 

cool, thanks guys. im glad to see there is some discussion about this other method of setting the pinion angle.

thanks for all the feedback everyone!

 

I think HemiRambler added a good insight here, as the phased u-joints will properly "speed-up and slow-down" with each revolution. The very issue that a CV joint eliminates in a FWD car. I believe a shaft can withstand a small degree measure of "equally bent misalignment" say 3-5 degrees at each end, and still transfer power w/o vibration penalties.

 

Exactly right!!
The real objective is to get the working angle of both joints the same. Then the angles can be the same or opposite. Most cars that I have seen have the pinion down so that the angles are smaller. I would not want angles more than 5 degree included. This thread started with 10 degree angles included. Way over too much. I measure the engine,shaft, and rear angles. I tilt the rear down so the angle between the engine and the shaft is the same as the angle between the shaft and the rear. As the rear suspension moves, this arrangement keeps the angles closer to what is wanted.

 

wow this is getting complicated. questions. 1. if i have my 103.5 wb "a" frame higher in the back by 2 degrees. the front should be approx 3.5" lower. is this excessive? 2. if i mount the engine (flathead) level at the intake, that would give me a -2 degrees relative correct? 3. if i mount the differential snout +2 degrees will that work? 4. do i weld the engine mounts (gusseted flat plates) level with the top frame rails or incline them -2 degrees to match the engine?THANKS

 

This goes against everything I thought I ever knew about drive line angles, but if it is true then it would make life a lot easier for cars with low slung motors, keeping the drive shaft low down.

The million dollar question: Has anybody actually run a car like this for any length of time though?