I gots the shakes

[biohazardbill]

Drove the truck for the first time today since I bought it in January. Since I have bought it I have installed air ride, all new front end components, new one piece drive shaft with joints, new axle shafts in the rear, new wheels and tires, tires balanced and aligned today.

On way home from alignment I still feel shaking in the steering wheel and it also feels like some shake in the rear when doing about 70. Have already checked everything a couple times for tightness....

Is this common?

[dznucks]

Did you change the ride height since having it aligned? When you do air it up and down, how will you make sure you return to the height the truck was at when it was aligned?

Is your pinion angle correct and was the driveshaft balanced? are the u-joints installed correctly?

[CC69Rat]

yeah .. I'm betting pinion angle.

Take a picture (?) of the nose of the rear end pinion where it connects to the drive shaft and we'll help confirm it for you. It sounds like what's commonly known as 'jump rope' effect.

[biohazardbill]

Had it aligned at ride height.

Ill snap a pic at ride height if I can.
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[CC69Rat]

Do you have an angle finder?

[biohazardbill]

Kinda hard to get to at ride height... let me know if you need a different angle.



I used to have an angle finder, wife ran over it on accident a few months ago... I can grab another one if need be no big deal.

[biohazardbill]

Originally Posted by dznucks

When you do air it up and down, how will you make sure you return to the height the truck was at when it was aligned?

I have the e3 setup so I just hit button 2 for ride height... levers and sensors do the rest.

[CC69Rat]

You say it only does it about 65-70mph ? There's something 'special' about the harmonics of 64mph. Dont ask me what it is .. but I have heard from several drive line guys that if the shaft is out of balance it will give you vibrations at 64mph. Thinking maybe the speedo is off a little .. ~ .. maybe

I don't think it's pinion angle now. It looks spot on to me.

[biohazardbill]

I dont have a speedo cable at the moment, Speedo app on i phone said it was 67-70 when the shaking started. 2100 rpm

[biohazardbill]

Hmmm would have thought the place that built the driveshaft would have balanced it....

[biohazardbill]

Dont know if this makes a difference but at the trans she seems to go upwards...



A friend suggested I raise the tail of the trans a bit.

[CC69Rat]

Ah ha! Yes.. shim the tail shaft up about a 1/4 in and see if it helps. I agree.
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[MARKDTN]

Looks to me both pinion angle and transmission angle are wrong, but it may be the photos. To me, the pinion needs to go down and the transmission up.

[biohazardbill]

Originally Posted by MARKDTN

Looks to me both pinion angle and transmission angle are wrong, but it may be the photos. To me, the pinion needs to go down and the transmission up.

By raising the tail shaft on the trans I think it will do just that... but would take more than a 1/4"

[brad_man_72]

Why aren't the weld yokes and trans yoke painted? We paint all of that while our shafts are in the ballancer. I know some shops ballannce their shafts without the ujoints or trans yokes, that's like ballancing your wheels before you install tires. Did a machine shop build the shaft? Most machine shops don't want to drop $30k on a driveshaft ballancer. 3r shafts are very finicky to ballance anyways because the aftermarket joints don't mount the same way as the factory joints. Looks like cheap ujoints also. Nice pinion yoke but with those ubolts its easy to overtighten and lock up a ujoint.
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[biohazardbill]

I supplied the yokes, they built the d-shaft off my dimensions.

[biohazardbill]

Well I raised the tail of the trans 3/4" Test drove and got up to 80 on the freeway between exits and seemed to do ok. I get a little shake still so going to try and go up another 1/4 tomorrow. Cant go to much higher due to cab floor.

[biohazardbill]

Ok couple of questions...

Did SWB trucks have 2 piece drive shafts? Would that solve this issue if the extra 1/4" doesnt work?

Would it be better to just grind off old perches and clock the axle and weld on new ones?

[CC69Rat]

When I suggested 1/4 I just wanted to see if it got better.. I didn't think about DS Clocking.. that's another idea.

So at 3/4" up, .. it's better? At 80mph does it feel like a tire out of balance? Did the shakes move? (Does it still feel like it's under the truck?)

[biohazardbill]

Its better... but I still feel vibration... at lower speeds like on my back country roads around 60 it feels like my front suspension has some shakes like an out of balance tire....
its funny you say that because I was going to have the balance checked by another shop as the first time I got the tires balanced all the weights fell off... so I had thought they may have fallen off again (they may have havent checked again yet)


It is like 3/4 of a mile from my exit to the next so I didnt run at a constant 80mph, I basically got up there and then let off to get off the exit so I dont have a real input for an amount of time at that speed. However before I would not have went past 65-70 due to the shakes.

It does seem though that under load the shake gets better but when let off to slow down it gets worse.

[brad_man_72]

Originally Posted by biohazardbill

I supplied the yokes, they built the d-shaft off my dimensions.

That doesn't explain why they don't have paint on them. Sounds like you found your problem with the trans.

Swb trucks came with. One piece shaft only if they were 6 cyl 3ott all others got the 2 piece shaft from my understanding.
Switching to 2 piece would only help your angle problem if your pinion is higher than the carrier bearing would be.
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[CC69Rat]

Curious how the pinion was adjusted? Shims?
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[CC69Rat]

Originally Posted by biohazardbill

...

It does seem though that under load the shake gets better but when let off to slow down it gets worse.

..

I think this is our key here.. IF I'm wrong here guys, help me out but this is the way I understand it. Under load / accelleration the pinion angle goes UP (toward the bed floor) So .. when he lets off, the shake gets worse. .. pinion angle rotates DOWN, toward the pavement.

Could it have too much shim in it?? (just thinking out loud) - Pinion too far down at ride height? It looks like it's pretty much zeroed out in the picture he posted earlier.

Hang in there man.. we'll get it figured out. I think you had a combination of the trans angle and possibly too much shim? ?? Again, kinda logically guessing here ..

[ItsRandy]

Vibration under acceleration means the pinion angle is off one way and under deceleration means the pinion angle is off the other direction, I just can't remember which is which. With trailing arm suspension the pinion doesn't move like it does in leaf spring applications because it is bolted "solidly" to the truck arms and the truck arms don't really flex (or they aren't supposed). Check this out: http://www2.dana.com/pdf/J3311-1-DSSP.pdf . Print it out, it will tell you everything you need to know about driveline angles and were afraid to ask.

[biohazardbill]

Originally Posted by CC69Rat

Curious how the pinion was adjusted? Shims?
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I didnt adjust the rear pinion.



Ok so here we go...

I went to lowes and got an angle finder. Put the truck at ride height and jacked up the rear by the trailing arms to maintain the angles, so even though they are off, the ratio between each other should be good.

I removed the driveshaft and put in another yoke I had laying around. Put the yoke in the vertical position.

From the driver side looking in, the needle was 3 degrees right of 90 which means it is pointing up 3 degrees.

From the pass side looking in the needle was 4 degrees left of 90 which means it is pointing down 4 degrees.

Would that be 1 degree difference or 7 in this aspect?

Now....

putting the truck back on the ground i redid the rear.

rear is now 6 degrees to the right of 90 giving me a 10 degree difference from original angle finding.

rear is 6 degrees up

add that 10 degrees to the front

front is 7 degrees down.

Does this sound right?