This is a demonstration of driveshaft working angles for u-joints. On the table here I have a
four-wheel drive drive line set up with the rear differential rear two-piece propeller shaft some
manufacturers call it a drive shaft some call it a propeller shaft of a transfer case and our
front propeller shaft and our front differential well all u-joints have a maximum working angle
that they are to operate at and unequal working angles can cause vibrations so the purpose of
this demonstration is to show you how to first measure u-joint working angles and then how to
adjust the working angles just a little bit of theory the u-joints will accelerate and
decelerate twice per revolution as the propeller shaft rotates and as one accelerates we want the
other one to be decelerating its its companion u-joint so on the rear propeller shaft here
there are two u-joints that work together to cancel out each other's accelerations and
decelerations and the way that you measure the working angle of u-joint is to somehow measure
the angle of the pinion gear itself and so right here on our rear differential of a 2007 tundra we
have a pinion flange right here and this flat side of the pinion flange is where you can put
an incline ometer there are digital versions that you can get for smartphones a lot of them are free
and we're just going to measure the angle of that flange right there while it's on the truck
with the suspension fully loaded obviously here on the bench we don't have the suspension fully
loaded or even here but we are just going through the process of showing you how to measure u-joint
working angles so the working I'm sorry so the angle of this front of the flange on the front
of the pinion gear on the rear axle is 2.8 degrees and then we have another in Phenom
etre that we put here on there the rear piece of the two-piece propeller shaft and it's measuring
an angle of 1.9 degrees so the working angle of this u-joint is the difference between those two
angles so you take the larger one the 2.8 and you subtract the smaller one the 1.8 and we get
a 1.0 degree working angle of this u-joint now in order for that u-joint to properly cancel
out the accelerations and decelerations of this other u-joint the one here in the middle by the
center support bearing the working angle of this u-joint also needs to be one degree or very very
close to it in other words we want the working angles to be equal on the center u-joint and on
the rear u-joint and whether you've got a lift kit on your truck or your vehicle is lowered
the closer you can get those two angles to being equal the better off you're going to be well to
get to measure this working angle to calculate that working working angle we're going to take
the angle of this rear propeller shaft which if you recall is 1.8 degrees and then we'll measure
the angle of the front portion of this two-piece propeller shaft and it is 4.6 degrees well once
again we're going to subtract the smaller from the larger so we have 1.9 degrees of the rear piece
of the two-piece propeller shaft we're going to subtract that from 4.6 so that would be two
point seven degrees is the working angle of this Center you joined now remember I said to cancel
out vibrations the best you can we want to have the center u-joint and the rear u-joint working
angles be the same well we had one degree of the working angle back there and 2.7 degree working
angle here that's not close enough they need to be within half a degree typically is the maximum spec
and preferably they need to be identical well to fix that we're going to have to change the
position of the center support bearing up or down or at the rear differential on the leaf springs we
would have to put shims a wedge type shim to point the pinion nose up or down farther so that that
angle would become more equal so we'll play with out here in just a minute the other thing about
a two-piece rear driveshaft is that the front u-joint does not have a companion u-joint to
cancel out its accelerations and decelerations and so that means that the angle of this front
joint the working angle needs to be almost zero and so if we look it has an angle coming out of
the transmission transfer case three point nine degrees and that's measured right on the flange
itself and the front piece of the two-piece prop shaft is four point six two so we are
0.7 degrees different between those two so as we have a 0.7 degree working angle of this front you
joined well the specification typically in the book is around half a degree on this particular
vehicle it allows for clear up there 0.8 nine degrees plus or minus one degree with for the
Toyota specifications so technically that front u-joint is within specification because we have
a 0.7 degree working angle which once again is just the difference between the the angle of the
output shaft of the transfer case and the front propeller shaft now one thing about the output
shaft of the transfer case and that front piece of the two-piece rear propeller shaft is that the
angle of this input shaft from the transmission through the center line of the transfer case as
a matter of fact through the whole center line of the transmission and the engine crankshaft all of
those should be lined up with each other including the front piece of this two-piece propeller shaft
if we had a three-piece propeller shaft it should also be lined up so what I want you to do is think
of the front piece of a multiple piece propeller shaft as simply being an extension of the output
shaft of the transfer case or the transmission it should be as straight as possible typically
we don't want a zero Degree working angle because the u-joint won't move and have any lubrication
there but half a degree or less is the typical specification and then the rearward piece back
here that moves up and down with the suspension it has the companion joints that work to cancel each
other's accelerations and decelerations out so for working angles once again all we do is to the
difference between the angles on each side of the u-joint so the rear pinion angle is measured at
the flange and then the propeller shaft angle the difference between those two is the working angle
of the rear joint the center joint it's working angle is just simply the difference between the
angle of the rear propeller shaft and the front propeller shaft and then that front joint the odd
joint it's working angle is simply the difference between the output shaft speed their output shaft
of the transfer case or transmission and the front piece of the front drive shaft and that's it's
working angle so the way to correct any of those angles is we can shim the transmission or transfer
case mount typically up we typically can't take it down the center support bearing it's bolted up
to the flange that are mounting that amounts to so we could put shims under it to bring it down
and then the pinion once again can be lifted up or down you can buy shims in half degree increments
that go on leaf springs under the u-bolts to tilt the pinion gear up or down to help correct
improper u-joint working angles so once you get those working angles equal on this rear propeller
shaft you should not have a vibration at least a second-order propeller shaft speed vibration and
I will have more videos on vibration diagnosis but if you're working angles are wrong or your
u-joints are bad you will typically end up with two shakes or two vibrations per revolution of
the propeller shaft and balancing tires balancing drive shafts propeller shafts won't do anything
you can you can replace the parts and it still won't fix it these angles must be correct and
you must be able to measure them and correct them with shims or body modifications to get rid of
the vibration this has been a demonstration of how to measure u-joint working angles on
a multiple piece rear driveshaft or propeller shaft it would work the same for a single piece
propeller shaft single piece front propeller shaft or multiple piece rear propeller shaft