Little Drive Line Angle Help Please

Harbin_22

Harbin_22

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Dec 4, 2010
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Need a little help figuring out of my angles are right or not. I've been chasing an odd vibration and wondering if the angles are causing it. Truck has 3" lowering shackles, overloads removed, and Tbars let all the way down. Hope I can explain this well enough...


Okay, at ride height on level surface, the output shaft yoke is on 5° sloping as if the nose of the engine is higher than the trans output. So higher towards front of truck.

The driveshaft is also on 5° sloping in the same manner, front is higher than back.

The rear end pinion is on around 3°, but it is lower in the front, so sloping the opposite way. So rear end pinion is tipped down towards the ground.

Some of the calculators and info I can find says this is all wrong lol. Not sure if the trans needs to be picked up some in the rear, along with the rear end tipped up some. Thanks for any help
 
IOWA LLY

IOWA LLY

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Input yoke angle should be the same as output yoke angle in an ideal situation. Farther from that you go the worse your situation will be.

As odd as it may sound since your driveshaft has to angle up 5* from transfer case in theory your pinion should point up 5* as well. Now that can vary because of twist and movement under acceleration etc but that is the general idea.

If it were my truck, and if your numbers are accurate, I would shoot for rotating your pinion angle up 5*. Meaning your transfer case angle is 5*, and your pinion angle is 2* under no load or acceleration. I'll bet that will get you close


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Harbin_22

Harbin_22

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Dec 4, 2010
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IOWA LLY said:
Input yoke angle should be the same as output yoke angle in an ideal situation. Farther from that you go the worse your situation will be.

As odd as it may sound since your driveshaft has to angle up 5* from transfer case in theory your pinion should point up 5* as well. Now that can vary because of twist and movement under acceleration etc but that is the general idea.

If it were my truck, and if your numbers are accurate, I would shoot for rotating your pinion angle up 5*. Meaning your transfer case angle is 5*, and your pinion angle is 2* under no load or acceleration. I'll bet that will get you close


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Click to expand...

Do you think the output yoke needs to come up a couple degrees? Or do.you think rotating the diff will change the angle of the drive shaft enough to make it okay? If all of them are at 5°, that puts me at 0° working angle and everyone says that's bad.
 
Chevy1925

Chevy1925

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Since you have both the pinion and output shaft pointed down, the driveshaft is fighting its self and causing the vib.

Because you are lowered, this is tricky. What you don’t want is the output shaft to be pointed down while the drive shaft is angling up towards the rear axle and have the pinion pointed up (that’s how a stock truck or lifted truck is). I would bring the output shaft up 5* and the pinion up 3*. This puts your driveshaft at a 2* working angle. It also means that if your rear axle ever goes up enough to cause the pinion side of the driveshaft to be higher ran the output shaft side, you won’t have a working angle issue between the two joints (driveshaft won’t bind).

5* is no small amount so if you can’t get it that high, get it as far as you can and keep the pinion at 0*. This will work the best and bibs should be very min or not even noticeable
 
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Harbin_22

Harbin_22

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Dec 4, 2010
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Chevy1925 said:
Since you have both the pinion and output shaft pointed down, the driveshaft is fighting its self and causing the vib.

Because you are lowered, this is tricky. What you don’t want is the output shaft to be pointed down while the drive shaft is angling up towards the rear axle and have the pinion pointed up (that’s how a stock truck or lifted truck is)
Click to expand...

Mine is definitely not low enough for that to happen, I hope lol. I'm going to double check my measurements tomorrow and order a few shims and see what happens.
 
Harbin_22

Harbin_22

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Okay, went out and double checked, feel like a dummy but the diff is pointed up already. So is my problem the drive shaft and joints are too straight? The diff is either 3-4°, the drive shaft is 4-5°, and output is 5-6°.
 
Chevy1925

Chevy1925

don't know sh!t about IFS
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Oct 21, 2009
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No. I’m not quite sure who says them being too straight is an issue. That’s definitely not the case lol.

This video is a good visual of what is going on if driveline related but a straight driveshaft with correctly aligned input and output shafts will not cause a vib or issue
https://m.youtube.com/watch?v=gmV4qwLfOMY

Pretty sure you have axle wrap bars, correct Kyle?

Shim the pinion up 3* so the pinion and output are the same. Axle wrap bars keep the pinion from rotating which is good but doesn’t let the pinion angle come up under accel/cruise and stop the vib
 
Chevy1925

Chevy1925

don't know sh!t about IFS
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Oct 21, 2009
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Na I know how it goes. It’s the little things that can drive ya nuts and just bug ya/eat at ya. Let us know if that change helps or not. Wouldn’t hurt to drop the shaft and spin each joint feeling for anything but a spin with a slight drag
 
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