karlos
03-19-2020, 11:40 AM
Got a question from a forum member in response to this old post: https://thefactoryfiveforum.com/showthread.php?22594-Driveline-Setup-(aka-Pinion-Angle)
The question had to do with receiving conflicting advice on whether the driveshaft angle needs to be measured as part of the driveline setup procedure. This comes up frequently on the forum, and there’s never a unanimous consensus. So very confusing. If for no other reason than a temporary escape from the Coronavirus madness, I thought I’d take the time to post the answer here.
A couple definitions first.
1. What we commonly refer to as pinion angle is the difference between the operating angles of the two u-joints
2. Operating angle is the difference between the angles of the two things the u-joints are connected to (trans and driveshaft at one end, driveshaft and diff at the other)
Based on those definitions, the operating angles depend in part on the driveshaft angle. And since pinion angle is related to operating angle, pinion angle is also tied to the driveshaft angle. So is it really true that driveshaft angle is irrelevant to pinion angle? Under one special circumstance, the driveshaft angle can be ignored for the purpose of determining the pinion angle. The driveshaft angle can be ignored if and only if the slope of the trans and the diff are consistent (either both up or both down). Why is this so?
When it comes to u-joint operating angles, the important thing to understand is that the angles subtract if the slope of the two connected components is consistent, and the angles add if the slopes are inconsistent.
So let’s say the measured angle at the transmission output shaft is 3 degrees with an upward slope, the angle of the differential pinion shaft is 2 degrees, also with an upward slope, and finally the angle of the driveshaft is 10 degrees again with an upward slope. All three slopes are consistent, so all angles subtract. Operating angle 1 is 10 - 3 = 7, and operating angle 2 is 10 - 2 = 8. The difference between the two operating angles is 8 – 7 = 1 degree. This is the pinion angle, which we could have also calculated more simply as the transmission angle minus the differential angle, 3 – 2 = 1. But note what happens if we make the slopes inconsistent.
Let’s say the transmission slopes down rather than up. Still 3 degrees, but now down rather than up. Since the slope of the transmission and the driveshaft is inconsistent, the angles now add. Operating angle 1 is 10 + 3 = 13 degrees. Operating angle 2 is 10 - 2 = 8, as before. But now the difference between the operating angles (the pinion angle) is 13 – 8 = 5 degrees. The transmission angle is still 3, the differential angle is still 2, but the pinion angle is most definitely not 3 – 2 = 1 degree.
If the slope of the trans and diff are consistent, then the driveshaft angle just becomes an offset, either adding or subtracting to/from the transmission and differential angles. Either way, you still end up with the same difference as that produced by the trans and diff angles by themselves. But this only works if the slopes are consistent. And it’s not at all uncommon to have inconsistent slopes. So gotta be careful.
It’s very important to recognize that even if the slopes are consistent and the pinion angle check simplifies to just a difference between the trans and diff angles, this still leaves you with no insight into the actual operating angles. Driveline manufacturers commonly recommend that u-joint operating angles not exceed 3 degrees. In the first example above, the max operating angle was 8 degrees, which is far out of spec. Pinion angle was good at 1 degree, but the operating angle was way out. Even worse in the second example at 13 degrees. This is why checking the operating angles is important – pinion angle by itself does not equate to a good installation.
Conclusion is that you must measure and account for the driveshaft angle in order to set your driveline up properly. Pinion angle by itself is only one part of the story. U-joint operating angles need to be verified along with the pinion angle. And driveshaft angle must be measured in order to check the operating angles.
There are a couple of good driveline calculators out there that can be used to do these checks (and note that all of them ask for a driveshaft angle). Spicer has one on their website (https://spicerparts.com/calculators/driveline-operating-angle-calculator), and Tremec makes an app that you can install and use on your phone (https://www.tremec.com/menu/tremec-toolbox-app/).
The problem with the Spicer tool is that it doesn’t tell you directly whether your driveline angles are good, it just gives you the operating angles. The Tremec tool is, IMO, difficult to use in that you must tap on the screen of the phone to take a measurement, and tapping on the screen tends to affect or change the measurement. If you’re an MS Excel user, the spreadsheet shown below will tell you whether all important driveline setup criteria have been met. Simply use a standard angle finder to take your measurements and enter them in the yellow cells. The calculated operating angles are shown in the blue cells. The cells in the ‘Criteria Check’ section will all be green if everything is within spec. Happy to make the spreadsheet available to anyone that would like a copy. And yes, I've checked it against the other tools. They all give the same answers.
I’m sure a lot of folks will think I’m just over-complicating things. On the contrary, what I’m really trying to do is prevent oversimplification that leads to improper driveline setup. If you’ve seen the carnage a failed u-joint can cause, then the importance of getting this right becomes clear.
With a good understanding of the underlying concepts and the objectives you’re trying to achieve, it’s possible to take shortcuts and still wind up in a good place. But why? You’re already under the car taking measurements, and the driveshaft angle is the easiest of the three to measure. Take the three measurements, enter the values into one of the driveline tools, and verify that all criteria have been met. No need to guess or assume or rely on your good luck.
The spreadsheet is a useful tool for helping to understand the effect of changes in slope and/or angle. In other words, the overall concepts that were discussed here are easier to understand if you play around with making changes and then observe what outcome they produce. Again, happy to make the spreadsheet available to anyone that wants it.
-Karl
https://thefactoryfiveforum.com/attachment.php?attachmentid=124322&d=1584635216
The question had to do with receiving conflicting advice on whether the driveshaft angle needs to be measured as part of the driveline setup procedure. This comes up frequently on the forum, and there’s never a unanimous consensus. So very confusing. If for no other reason than a temporary escape from the Coronavirus madness, I thought I’d take the time to post the answer here.
A couple definitions first.
1. What we commonly refer to as pinion angle is the difference between the operating angles of the two u-joints
2. Operating angle is the difference between the angles of the two things the u-joints are connected to (trans and driveshaft at one end, driveshaft and diff at the other)
Based on those definitions, the operating angles depend in part on the driveshaft angle. And since pinion angle is related to operating angle, pinion angle is also tied to the driveshaft angle. So is it really true that driveshaft angle is irrelevant to pinion angle? Under one special circumstance, the driveshaft angle can be ignored for the purpose of determining the pinion angle. The driveshaft angle can be ignored if and only if the slope of the trans and the diff are consistent (either both up or both down). Why is this so?
When it comes to u-joint operating angles, the important thing to understand is that the angles subtract if the slope of the two connected components is consistent, and the angles add if the slopes are inconsistent.
So let’s say the measured angle at the transmission output shaft is 3 degrees with an upward slope, the angle of the differential pinion shaft is 2 degrees, also with an upward slope, and finally the angle of the driveshaft is 10 degrees again with an upward slope. All three slopes are consistent, so all angles subtract. Operating angle 1 is 10 - 3 = 7, and operating angle 2 is 10 - 2 = 8. The difference between the two operating angles is 8 – 7 = 1 degree. This is the pinion angle, which we could have also calculated more simply as the transmission angle minus the differential angle, 3 – 2 = 1. But note what happens if we make the slopes inconsistent.
Let’s say the transmission slopes down rather than up. Still 3 degrees, but now down rather than up. Since the slope of the transmission and the driveshaft is inconsistent, the angles now add. Operating angle 1 is 10 + 3 = 13 degrees. Operating angle 2 is 10 - 2 = 8, as before. But now the difference between the operating angles (the pinion angle) is 13 – 8 = 5 degrees. The transmission angle is still 3, the differential angle is still 2, but the pinion angle is most definitely not 3 – 2 = 1 degree.
If the slope of the trans and diff are consistent, then the driveshaft angle just becomes an offset, either adding or subtracting to/from the transmission and differential angles. Either way, you still end up with the same difference as that produced by the trans and diff angles by themselves. But this only works if the slopes are consistent. And it’s not at all uncommon to have inconsistent slopes. So gotta be careful.
It’s very important to recognize that even if the slopes are consistent and the pinion angle check simplifies to just a difference between the trans and diff angles, this still leaves you with no insight into the actual operating angles. Driveline manufacturers commonly recommend that u-joint operating angles not exceed 3 degrees. In the first example above, the max operating angle was 8 degrees, which is far out of spec. Pinion angle was good at 1 degree, but the operating angle was way out. Even worse in the second example at 13 degrees. This is why checking the operating angles is important – pinion angle by itself does not equate to a good installation.
Conclusion is that you must measure and account for the driveshaft angle in order to set your driveline up properly. Pinion angle by itself is only one part of the story. U-joint operating angles need to be verified along with the pinion angle. And driveshaft angle must be measured in order to check the operating angles.
There are a couple of good driveline calculators out there that can be used to do these checks (and note that all of them ask for a driveshaft angle). Spicer has one on their website (https://spicerparts.com/calculators/driveline-operating-angle-calculator), and Tremec makes an app that you can install and use on your phone (https://www.tremec.com/menu/tremec-toolbox-app/).
The problem with the Spicer tool is that it doesn’t tell you directly whether your driveline angles are good, it just gives you the operating angles. The Tremec tool is, IMO, difficult to use in that you must tap on the screen of the phone to take a measurement, and tapping on the screen tends to affect or change the measurement. If you’re an MS Excel user, the spreadsheet shown below will tell you whether all important driveline setup criteria have been met. Simply use a standard angle finder to take your measurements and enter them in the yellow cells. The calculated operating angles are shown in the blue cells. The cells in the ‘Criteria Check’ section will all be green if everything is within spec. Happy to make the spreadsheet available to anyone that would like a copy. And yes, I've checked it against the other tools. They all give the same answers.
I’m sure a lot of folks will think I’m just over-complicating things. On the contrary, what I’m really trying to do is prevent oversimplification that leads to improper driveline setup. If you’ve seen the carnage a failed u-joint can cause, then the importance of getting this right becomes clear.
With a good understanding of the underlying concepts and the objectives you’re trying to achieve, it’s possible to take shortcuts and still wind up in a good place. But why? You’re already under the car taking measurements, and the driveshaft angle is the easiest of the three to measure. Take the three measurements, enter the values into one of the driveline tools, and verify that all criteria have been met. No need to guess or assume or rely on your good luck.
The spreadsheet is a useful tool for helping to understand the effect of changes in slope and/or angle. In other words, the overall concepts that were discussed here are easier to understand if you play around with making changes and then observe what outcome they produce. Again, happy to make the spreadsheet available to anyone that wants it.
-Karl
https://thefactoryfiveforum.com/attachment.php?attachmentid=124322&d=1584635216