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How much drive shaft angle is too much drive shaft angle?

DirtDonk

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It’s true “by the book“ but not always in the real world.
If you have a full linked suspension or some other traction aiding device to keep the springs and rear axle from wrapping, that can work. But with our high degree of springwrap found on Broncos with leaf springs we have found 1 to 2° down bubble to be the best compromise.
 

Broncobowsher

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It’s true “by the book“ but not always in the real world.
If you have a full linked suspension or some other traction aiding device to keep the springs and rear axle from wrapping, that can work. But with our high degree of springwrap found on Broncos with leaf springs we have found 1 to 2° down bubble to be the best compromise.
I ran a torque arm for years and actually ran a negative pinion angle (pinion pointing up past zero angle) all the time. It helped with CV angle. and since the torque arm locked the pinion angle I never had to worry about spring wrap winding the U-joint up into an unsafe angle.
 

DirtDonk

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That’s a great way to reduce that double cardan angle.
I’ve never had very high angles on any of my stuff so the low aiming pinion has worked for me.
But that’s something I’ll definitely keep in mind now.
 

Broncobowsher

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I've had a few of these where the differential u-joint angle was exactly zero and the needle bearings brinelled the joint posts and ended up stuck in place...
Normally the spring flex is enough that even if they at 0 at static, the needles still move enough in use this won't happen.
I have seen it on IRS cars with the diff mounted solid to the chassis and there is no spring flex to keep the U-joint exercised.
 

toddz69

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You should read the Ford TSB in post #11 of this thread.
Interesting that they specify a .5-3 deg angle for all the joints in a shaft. It's been a long time since I've had a stock height EB but I'm guessing the joint angles in a stock height truck double cardan exceed that?

Todd Z.
 

jamesroney

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Interesting that they specify a .5-3 deg angle for all the joints in a shaft. It's been a long time since I've had a stock height EB but I'm guessing the joint angles in a stock height truck double cardan exceed that?

Todd Z.
The TSB is crap. (I think I mentioned that above...) It is very generic, and it has minimal applicability to a double Cardan driveshaft in an early Bronco.

The vast majority of driveshaft applications do in fact run under 3 degrees per joint. This is usually accomplished by installing the engine downhill, and the rear pinion uphill. Most applications (at static ride height) run the crankshaft centerline directly co-linear with the rear pinion centerline. So all of the requirements of the TSB can be met. But the TSB does NOT tell you what do do when the physics exceed the constraints of the model.

You can tell that the TSB is intellectually bankrupt, because it advocates the use of larger components in the event that recommended angles are exceeded. This is not at all interesting from the perspective of harmonics. (which is the stated objective of the TSB.) Once again, the TSB is a generic Spicer Dana application engineering document used primarily to deflect warranty claims against the Tier 1.

You are absolutely correct that the 0.5 to 3 degree requirement is "not a requirement." My stone stock 67 U13 Military Bronco at static ride height runs the 6 cylinder engine at a 4 degree inclination. (de-clination if you prefer) The rear 9 inch pinion runs a 12 degree inclination. The front Dana 30 runs a 7 degree inclination. So the crankshaft points down 4 degrees toward the rear axle, the axle points up 12 degrees to meet the output yoke. The rear driveshaft front u-joint runs at an additional 8 degrees. So the rear axle exceeds the 3 degree engineering recommendation in the TSB by a little. But the Front driveshaft exceeds the 3 degrees by a LOT. The front output of the transfer case points UP 4 degrees. But the driveshaft points DOWN 7 degrees, resulting in an 11 degree total angle at the front driveshaft rear yoke. 11 is greater than 3. (This is why the front driveshaft CV binds first on lifted Broncos.)



I realize that I typed more than 5 words again...but I like Steve83, and don't want to argue. But I can't let my 2 Engineering Degrees and Six Sigma Black Belt go to waste. I'm off my soap box now.
 

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Steve83

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Interesting that they specify a .5-3 deg angle for all the joints in a shaft.
The minimum angle is to prevent brinelling. The max is so that there's some travel available when the suspension moves.
...I'm guessing the joint angles in a stock height truck double cardan exceed that?
That's the whole purpose of the DC - to effectively double the flex angle of the shaft. But the rules in the TSB still apply to EACH U-JOINT in the DC.
 

bmc69

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I realize that I typed more than 5 words again...but I like Steve83, and don't want to argue. But I can't let my 2 Engineering Degrees and Six Sigma Black Belt go to waste. I'm off my soap box now.
LOL...great lines. I design the drivelines for smaller vessels (75-150 ') ....drivelines that often include DC sections. To accommodate up to 3000 HP.... Suffice to say, very careful attention is paid to designing those. ;-) I always enjoy sitting back and watching some of the comments on truck driveline geometries....
 
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