Transmission, driveshaft, differential angles

[ThickCobra]

Returned from London Show and decided to do an under body inspection. Probably do it more often than I need to but feel it can't hurt.

Thought I'd revisit the transmission, driveshaft and differential angles. Not that they should ever change but, checked them anyway. That said, I may not have done it correctly the last time. And I know that this topic is covered a lot. I did research and found the tutorial someone shared. So, I'll get right to it.

Tko 600 , 3/4" of shims
2015 mustang IRS

Trans 2.5 degrees down
Drive shaft 5 degrees up
IRS 0.5 degree down

Results in op angle 1 of 7.5 degrees
Op angle 2 of 4.5 degrees
Both violating 3 degrees max limit on either end and greater than 1 degree difference between the 2 angles.

Since the trans is the only thing I can adjust, I'll need to add more shims under the trans. By my estimate, if I can reduce the trans angle to 1/2 degrees, I may see a drive shaft angle reduction down to 1 degree. And, with the differential angle unchanged at 1/2 degree, I should be good, with angle 1 at 1.5 degrees and angle 2 at 1/2 degrees.

Before I do anything, does the majority agree?

[boat737]

I'm not sure, but your "up" and "down" notations may not be consistent. I believe you should be referencing the up and down relative to Front to Rear on all components, i.e. the "Drive input" side vs. the "Drive output" side. So if your differential is "Down X degrees", then the front (pinion yoke) would be higher than the back (axle).

The way I'm reading this, is that your IRS is actually .5 deg. up (front to rear), which would give you the 4.5 deg operating angle.

If that is correct, then yes, increasing the trans shim height will reduce both operating angles. In addition, it well reduce the forward op. angle a bit more, since you are also changing the trans. angle as well as the driveshaft angle. And it looks like that will be what you want in this case.

Here's a good explanation on the topic. https://thefactoryfiveforum.com/showthread.php?22594-Driveline-Setup-(aka-Pinion-Angle)

In my case (with a 3 link and TKO), I started with 3/4 inch shim, and was just a tic out of tolerance. I went to a 1 inch shim, and even though very close, was just over tolerance the other way. I made a 7/8 inch shim and it is just about perfect.

[karlos]

I get 5.5 degrees for operating angle 2 as it sits now. A little different than your numbers but, yeah - no good either way. If the transmission angle changes to 0.5 degrees down, the driveshaft changes to 1 degree up, and the diff remains unchanged at 0.5 degrees down, you'd have operating angle 1 = operating angle 2 = 1.5 degrees. That'd be about perfect:

- angles on each end of the driveshaft are equal within 1 degree (1.5 - 1.5 = 0.0)
- maximum operating angle at either end is less than 3 degrees (1.5 at both ends)
- at least 1/2 of a degree continuous operating angle

[RJD]

Any pros/cons in using the free phone app from TREMEC - TREMEC TOOL BOX, Driveline Angle Finder? You use your smartphone to take three readings - transmission output shaft, driveshaft, and rear axle, and it determines whether your driveline angle is within acceptable limits.

110723

[NAZ]

Great for taking rough angles, always handy on my belt. But for serious adjustment I've found it not as accurate as my real angle finder. I suspect this is a phone thing but until you check it against a known good angle finder, use at your own risk.

[karlos]

Agree with Boat that there may be an inconsistency in how the driveline slopes are being interpreted, and that probably explains the difference in the calculated angles. Doesn't really matter which way you consider to be up or down, but the convention must be consistently applied to all three components (engine, driveshaft, differential) in order to avoid errors. One commonly used convention is that the slope of the drivetrain is measured going from front to rear. A component slopes downward if it is lower at the rear than the front. A component slopes upward when it is higher at the rear than it is in front. So in the graphic shown below, the engine is down, the driveshaft is up, and the differential is up.


https://thefactoryfiveforum.com/attachment.php?attachmentid=110724&d=1563161958

[GoDadGo]

We've shown this video many times so I hope it helps you as it has helped me.

https://youtu.be/Idk3BVDVHq4

This simple tool worked fine for me I guess because I'm a simple man with simple needs who doesn't even own a smart phone.

https://www.homedepot.com/p/Johnson-Magnetic-Angle-Locator-700/100161689?cm_mmc=Shopping%7CG%7CBase%7CD25T%7C25-1_HAND+TOOLS%7CNA%7CPLA%7c71700000034127224%7c5870 0003933021546%7c92700031755124805&gclid=EAIaIQobChMIj9vSxvm24wIVBdvACh1yyg9ZEAQYASAB EgLDpfD_BwE&gclsrc=aw.ds

Good Luck & Happy Shimming!

[CraigS]

I am also not sure I understand your up and down. I think of it this way. The engine and the diff should be parallel (solid axles are slightly different) and, personally, I don't worry about the drive shaft at all. Those ujoints can run at a pretty good angle as evidenced by what they can accommodate on a solid axle car. The diff can be offset from the engine either up/down or left/right but they must be parallel.

[rich grsc]

I am also not sure I understand your up and down. I think of it this way. The engine and the diff should be parallel (solid axles are slightly different) and, personally, I don't worry about the drive shaft at all. Those ujoints can run at a pretty good angle as evidenced by what they can accommodate on a solid axle car. The diff can be offset from the engine either up/down or left/right but they must be parallel.
Agreed, driveshaft angle need not be measured, the center line of the engine and the center line of the differential need to be parallel.

[karlos]

Agreed, driveshaft angle need not be measured, the center line of the engine and the center line of the differential need to be parallel.

Rich, Craig,

This is a common misconception that comes up frequently in multiple threads going way back. But it is a misconception. Parallelism by itself is not enough. Here's why.

First pic below shows the engine, driveshaft, and differential all parallel. This produces the ideal pinion angle of zero degrees. But it also makes the minimum u-joint operating angle equal to zero. A continuous operating angle of at least 1/2 degree is needed to prevent flat-spotting the u-joint needle bearings. In this case parallelism is achieved and the pinion angle is good, but u-joint life will be compromised.

Second pic below shows the engine and the differential once again parallel to one another. As in the first case this gives the ideal pinion angle of zero. But depending on how far the engine and the diff are offset from one another, this scenario has the potential for u-joint operating angles that exceed the recommended 3-degree maximum. As before, parallelism is achieved and the pinion angle is good, but driveline vibration and rapid wear will result.

Checking the pinion angle is only 1/3 of the complete driveline setup procedure. The minimum and maximum u-joint operating angles need to be verified as well, especially with the extremely short driveshafts we run on these cars. And the operating angles can only be determined by accounting for driveshaft angle in relation to the engine and differential angles. Check out this Spicer drivetrain video:
https://spicerparts.com/videos/measuring-driveline-operating-angles



https://thefactoryfiveforum.com/attachment.php?attachmentid=110778&d=1563247424



https://thefactoryfiveforum.com/attachment.php?attachmentid=110779&d=1563247740

[ThickCobra]

Everything gets adjusted today and I will post the results. I purchased a digital protractor to achieve more accurate readings so, I will post before and after measurements

[phileas_fogg]

Any pros/cons in using the free phone app from TREMEC - TREMEC TOOL BOX, Driveline Angle Finder? You use your smartphone to take three readings - transmission output shaft, driveshaft, and rear axle, and it determines whether your driveline angle is within acceptable limits.

110723

I found that the size of my phone prevented me from getting its side flush with the measuring surface. A bolt or piece of frame always messed up the measurement. My digital angle finder, however, is only about 1 1/2" long, and so much easier to mount such that I got repeatable measurements I believed.


John

[CraigS]

Karlos I understand. My thinking is that we can only adjust in side view so let's get the engine and diff parallel. We also know that the engine trans is offset to the passenger side slightly. I haven't bothered to measure it but I believe the diff pinion is off center slightly. I figure these top view offsets take care of any need to run a small angle for longer u-joint life.

[NAZ]

The Ford 8.8 pinion is offset 9/16", not sure how much the roadster engine is offset. Then how many actually use a straight line to ensure the engine/trans is not setting in the chassis skewed? Or that the rear axle is not skewed? I suspect most will simply bolt them in wherever they seem to fit. And for the non-adjustable rear control arms, how does FFR expect you to correct a skewed rear axle if you found one? Lack of adjustment does not dismiss the importance or nullify physics.

Also to consider is that the max driveshaft operating angle will affect the max safe RPM, i.e., more angle = lower max RPM. Dana/Spicer used to have a chart showing the various angels and the max RPM limits.

[karlos]

Still think there’s a lot of confusion as to what pinion angle is, how it should be measured, and what result we’re attempting to achieve. Maybe it would help to provide a step-by-step explanation of the setup procedure. Here’s one way it can be done.

Start with all the major components installed: engine, transmission, driveshaft, differential. Bolt the transmission mount to the chassis but don’t attach it (yet) to the transmission. Place a jack under the transmission and lift the rear until there’s approximately a ¾” gap between the transmission and the transmission mount. Most installs seem to end up in the vicinity of a ¾” gap, so this represents a good initial starting point.

With an initial gap of ¾”, use an angle finder to measure the angles at the transmission, the driveshaft, and the differential. Also note whether each of those three components is sloped upwards or downwards as measured from front to rear. The measurements can now be used to calculate operating angles 1 & 2 and the pinion angle. The thread linked above describes how to do the calcs, or you can use the online calculator at the Spicer website.

The online calculator works well enough, but it doesn’t tell you directly whether all three angles are within spec. I have an Excel-based worksheet that does the same thing the Spicer calculator does but goes one step further by checking all three angles to confirm acceptability. A screenshot is shown below. All three cells at the bottom of the spreadsheet will be green if everything is within spec.

If your initial measurements turn all three cells green, then make a shim with the same thickness as the measured gap and install it between the transmission and the transmission mount. Bolt everything together and you’re done. If not all green, then use the jack raise or lower the transmission in small increments (about 1/8” will have a substantial effect on the angles), re-record the angles, and re-enter the values into the worksheet. Keep making small changes up or down until all three criteria checks come back green. Once that happens, make a shim with the same thickness as the measured gap, bolt it up, done.

Should also mention that, for an IRS-equipped car, the only adjustment available to you is at the transmission mount. For cars with a live axle, the differential is also adjustable and can be used in conjunction with the transmission to set the driveline angles. The process for measuring and checking the angles is the same either way.

Happy to share a copy of the worksheet if there’s any interest. PM me with your email address and I’ll send a copy.


-Karl




Initial check: criteria 1 & 2 not met.
https://thefactoryfiveforum.com/attachment.php?attachmentid=110788&d=1563280056



After adjustment, all three criteria are now green. Good to go.
https://thefactoryfiveforum.com/attachment.php?attachmentid=110786&d=1563279965