Drive Shaft angle vs Pinion angle

I am wondering as I have a -1 deg downward angle on my driveshaft toward the rear of the car. My pinion angle is pointed downward -3.5 deg.
Should I raise the pinion angle upward 2 deg so when the car launches the D/S and pinion are nearly at 0?

Thanks Tore

I call that a 2.5 degree pinion angle.

depending on what type of suspension you have that may be just fine.

dkp

I measure that at -4.5°. 91° driveshaft angle and a pinion flange angle of 86.5°.

86.5°
-91.0°
_______
-4.5°


Within range on stock suspension with all rubber. We like it between -1° and -1.5° with solid heims.

my bad 4.5 degrees it is.. got my gozintas mixed up with my take aways.

Yup, what's the "best" driveline operating angles all kinda depends on the rear suspension type. Plus bushing type (rubber, urethane, or spherical) and/or rod-end type (metal, rubber, or urethane). The car being street/highway, or drag only can also be a factor as well.

A leafspring car with no/zero "traction devices" installed & sticky tires is going to need a ton of negative pinion operating angle because of all the possible upward pinion rotation it can produce under launch loading. On the other hand a beefy aftermarket 4-link with metal rod-ends might need as little as -0.75* to -1.00* negative pinion operating angle because it allows so little upward pinion rotation to happen under launch loading.

This is a ladder bar car.

The only way to know is to measure it when it is under power. You want it at 0° when you are full tilt.

Tore wrote:This is a ladder bar car.

IMO -4.5* pinion angle [or U-joint operating angle, or pinion/driveshaft mesh angle , or etc, etc, call it whatever] is a lot for a ladder bar drag car. Could be a lot of unnecessary U-joint friction going on.

If you're worried about going past 0.00* under launch loading you could always try mapping-out what the static pinion/U-joint/driveshaft operating angle is doing during suspension travel. If you have coilovers (with the car on jackstands) unhook them & raise the rear housing up to a height mimicking where it would sit if the shocks were fully compressed (bottomed out against the coilover shock's bumper/snubber). Then measure pinion angle at that point. Then start dropping the housing & measure pinion angle at various other points along the entire rear suspension travel until you reach the point where the housing would be sitting at full shock extension. Each stopping point where you measured pinion angle will flesh-out a map showing the minimum & maximum possible pinion angle the U-joint might see for a given static pinion angle (set at ride height) adjustment. Obviously there shouldn't be any wild swings in observed pinion angle changes during full suspension travel. But you might see some changes, some suspension types will have more than others during travel. Ladder bar/4-link bar angles can also have an effect where in the suspension travel pinion angle change might happen most/least.

Ladder bar structure flexing/bowing under launch loading can also change/reduce (temporarily) the pinion angle a little too depending on how beefy the LB's are. Some say another 1/2 a degree is lost due to LB flex/bow under load, some say 1 full degree.

DILLIGASDAVE wrote:

Tore wrote:This is a ladder bar car.

IMO -4.5* pinion angle [or U-joint operating angle, or pinion/driveshaft mesh angle , or etc, etc, call it whatever] is a lot for a ladder bar drag car. Could be a lot of unnecessary U-joint friction going on.

If you're worried about going past 0.00* under launch loading you could always try mapping-out what the static pinion/U-joint/driveshaft operating angle is doing during suspension travel. If you have coilovers (with the car on jackstands) unhook them & raise the rear housing up to a height mimicking where it would sit if the shocks were fully compressed (bottomed out against the coilover shock's bumper/snubber). Then measure pinion angle at that point. Then start dropping the housing & measure pinion angle at various other points along the entire rear suspension travel until you reach the point where the housing would be sitting at full shock extension. Each stopping point where you measured pinion angle will flesh-out a map showing the minimum & maximum possible pinion angle the U-joint might see for a given static pinion angle (set at ride height) adjustment. Obviously there shouldn't be any wild swings in observed pinion angle changes during full suspension travel. But you might see some changes, some suspension types will have more than others during travel. Ladder bar/4-link bar angles can also have an effect where in the suspension travel pinion angle change might happen most/least.

Ladder bar structure flexing/bowing under launch loading can also change/reduce (temporarily) the pinion angle a little too depending on how beefy the LB's are. Some say another 1/2 a degree is lost due to LB flex/bow under load, some say 1 full degree.

That's interesting Thanks Tore

Forgive me if Im wrong, but I always heard that you do not want "0" degrees in the driveline, as the driveshaft will have a tendency to "whip" and destroy other components.
I have heard that you want some offset degrees within the U joint to prevent the whip from happening.

BBFTorino wrote:Forgive me if Im wrong, but I always heard that you do not want "0" degrees in the driveline, as the driveshaft will have a tendency to "whip" and destroy other components.
I have heard that you want some offset degrees within the U joint to prevent the whip from happening.

All depends on the car's intended use.......

A street/highway driven car racking up thousands and thousands of on/off throttle & part throttle (minimal loading) miles having driveline angles at 0.00* will definitely beat the crap out of the U-joints over time. This is because for a long lifespan U-joints by design need some small amount of misalignment so they self-lubricate, & so the needle bearings don't pound on the exact same spot on the bearing surfaces over & over again. That's why the street/highway stuff is usually best served with an "equal-but-opposing" driveline profile. The slip yoke & pinion U-joint operating angles both equal the same number of degrees, but are opposing in their layout. An example would be if the slip yoke-to-driveshaft operating angle was +2.00* then the pinion-to-driveshaft would need to be -2.00* to be an equal-but-opposing profile.


A drag only car on the other hand spends so little time actually under heavy "launch loading" forces that having the static/at rest driveline angles damn close to 0.00*, (or actually at 0.00* under the temporary launch loading forces) that it's not really a big deal. Plus you reduce the frictional losses through the drivetrain as much as possible with it at 0.00* under load. The other factor is U-joints on a drag car need to be thought of as a maintenance/throw away item, and not something that is expected to last 100,000 miles. When you build a ladder bar or 4-link "drag only" car during the ride height & engine height mock-up process you point the crank/tailshaft C/L at the pinion C/L, & the pinion C/L at the crank/tailshaft C//L. Once the car is finished you dial in a very small amount of negative pinion angle. In this example if the drag car's "build" angles were at 0.00*, then the "finished" static/at rest pinion angle was adjusted at -1.00*, then the slip yoke angle will end up sitting somewhere in the neighborhood of +0.50*. The "drag only" driveline profile should never be used on a street/highway combo.

Also don't forget that driveline operating angles (both at the slip yoke & at the pinion) need to be measured while the car is sitting at ride height with the car's full weight loading/compressing the suspension.

Measuring the angles with the car on jackstands & the rear suspension hanging fully extended is not going to give accurate numbers.

BBFTorino wrote:Forgive me if Im wrong, but I always heard that you do not want "0" degrees in the driveline, as the driveshaft will have a tendency to "whip" and destroy other components.
I have heard that you want some offset degrees within the U joint to prevent the whip from happening.

Hardtail dragsters have been 0° for a long time.

But canceling out two planes is still 0°. One is a + and one is a -. 2° + -2°=0°

like mentioned above, same angle is okay if on different planes. the way we do our cars is we center the motor (rather than using factory offset). that gives us different planes as well to help make the u-joints live. Another thing we do that a lot of guys argue about is on u-joint placement on the driveshaft. Some like them 90° from each other. we put them on the same plane.

whatbumper wrote:......Another thing we do that a lot of guys argue about is on u-joint placement on the driveshaft.  Some like them 90° from each other.  we put them on the same plane.

^^^This.

I have no idea where the idea of rotating each U-joint end/mount 90* from each other originally came from. It kinda sounds to me like a fix for a non-problem. IIRC every aftermarket 'moly or CF driveshaft I have messed with had the DS ends on the same plane.