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Randall Smith
| | Posted on Saturday, February 08, 2003 - 12:39 am: | 
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Back in Dec you helped me by when I asked this question: Do the u-joint angles change when you accel or decellerate? You answer was that the front pinion gets torqued more upward when you take you foot off the gas. And the oposite happens on the rear pinion.
Apparently that is why when I take my foot off the gas above 55mph, my front drive shaft vibrates. And I bought an inclinometer to check the angles. My front pinion IS pointing up 4 degrees more than it should be, according to the diagrams on www.4x4shaft.com Will fix this soon.
Since then I have made an adjustable panhard rod to tune the u-joint angle as seen from below(lateral angle). Could you please tell me this: Does the front axle assembly tend to move toward the drivers side or passenger side when you accellerate or decellerate??
Randall |
muskyman
| | Posted on Saturday, February 08, 2003 - 01:03 am: |
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randall,
well I am sure I said rear is torqued up and front down
this movement doesent move and stay there it moves only a small amount under load.
the panhard rod does not control pinion angle.
the axle should not move side to side at all ever, thats what the panhard rod does. it resists the side to side movement.
also pinion rotation is very small on these trucks when the bushings are fresh. when they are old and breaking down you start to get pinion movement and that movement can cause vibes.
sorry if you misunderstood me
thom |
muskyman
| | Posted on Saturday, February 08, 2003 - 01:05 am: |
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do you have a lift?
if so how much?
thom |
muskyman
| | Posted on Saturday, February 08, 2003 - 01:18 am: |
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sorry misread your post
lets just talk front end here
under acceleration the front pinion force wants to rotate the pinion down when you let off that force wants to rotate it up.
the bushings that resist this force are located in the Radius arms. there are two bushings in each arm. they are directly under the front axle housing. if they become worn or torn the pinion then will exihibit more rotation then there is meant to be and vibes may result. |
Randall Smith
| | Posted on Saturday, February 08, 2003 - 01:43 am: |
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We had that big ice storm in NC when you anwered my post in Dec. I plan to get rid of this vibe.
So my driveshaft does vibrate when I let off the gas. And I can measure the angle. The pinion is pointing too high up(and goes higher under decel)
Every component of my suspension has been customized. wear isn't a factor. My problem is caused by not taking u-joint angles into consideration when changes were made to susp.
Now I realize that is why my DS vibes while other trucks do not. There are also 100 websites that people have made regarding fixes for DS vibes on every type of vehicle.
My front diff is also misaligned with the transfer case by an inch. Hence the adjusable panhard rod to adjust the lateral angle. turn of a wrench adjusts lateral location of axle. But I have to change length of drag link to match.
thanks
Randall |
muskyman
| | Posted on Saturday, February 08, 2003 - 11:41 am: |
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randall,
the pinion and diff are not in line from the factory.
LR compensates for this by putting the front shaft out of phaze(youke not aligned) this is aonle a band-aid approach.
since you are totally moded out there is a better way then moving the axle .
tom woods drivshafts does a double double cardin shaft that fixes this problem. you can call him directly and get the complete low down on it. it is a very proven fix that a number of guys on the POR board are running and I believe a few around here as well. it will also compensate for the pinion angle you have.
with that much pinion raise you must have a pretty tall lift?..have you done a castor compensation?
thom |
Randall Smith
| | Posted on Saturday, February 08, 2003 - 06:35 pm: |
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Thom
I actually only have 1.5" lift now and a plain ole TW DCDS. That DS helped more than anything else that I have tried. However it was installed without regard to it's effect on the front u-joint angle. If the front u-joint is more than 3 degrees out then the DCDS will vibrate, because there is nothing on the DS to cancel out vibes at the diff end. The diff end is supposed to be pointed straight at the TC.
I think you gave me the obvious answer to my question about how accelleration would effect axle location. The adjustable panhard rod is really just an interesting way to experiment with the suspension. It is also easier to instal than the fixed length rod.
Randall |
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