I was driving the Raider from the exhaust shop today (guy wants $150 for a cat back system <img src="/forums/images/graemlins/kewl.gif" alt="" />). But I was noticing on the ride there and back, at slower speeds the Raider would have a noticeable vibration. between 15-25 mph the vibration is almost unbearable. 30-60 the vibration goes away, but could be felt by holding onto the transfer case shifter. I have a feeling that since it started right after I installed the Valley coils that the old Ujoints are worn into the pattern of the old springs. After I get the exhaust installed I will throw in the new joints and report back. <img src="/forums/images/graemlins/kewl.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" />

Normally that vibration comes because the angle between the rear shaft (cardan) and the rear pinion is not the same as the tail of the output shaft comming from the transfer and the same rear shaft (cardan)... when you lift the rear suspension you must change the angle... it can be corrected changing the angle of the rear differential pointing up or down to the rear shaft keeping the same angle of the transfer output shaft and the rear shaft.

Small vibes will kill you your u-joints badly...

JorgeA

Yours sits just like mine with OME 910s <img src="/forums/images/graemlins/lol.gif" alt="" />. I just picked up some gen 2 upper contol arms to correct that some day.
A slow speed sounds like a wieght lost or a tire with a broken belt.
I just put one joint in the frt. of the rear shaft and had it balanced. Cost $115 labor here in Kaliforny , which aint bad at all for here.
I have a little play in the output shaft of the T-case that I beleive contributes to vibe. I had the bushing in the T-case R output made and pressed in by "Omega Machine" in Sacramento <img src="/forums/images/graemlins/kewl.gif" alt="" />.
U joints on these need to have the right thickness in the c clips for good balance.
Koyo joints are the best by far , but Mitsu doesn't sell parts for our vehicles anymore so I went with Precesion brand from napa.
Good luck...

After I did the suspension-lift on my 88 (extended shackles on a leaf-sprung rear) a couple years ago, I was getting a vibe at highway speeds. Installed a couple axle shims (which changed the pinion angle) and the vibe went away.

thats a advantage i have with a longer wheel base.it can handle a the shaclkes easyer with out getting pissed at me.

JorgeA beat me to it. I was going to try and sound smart for once because I learned about that last semester in my engineering class. Darn it. Anyway, its the angle difference between your U-Joints. As the U-Joints rotate the input and output speeds change in a Sine-Wave fashion. In order to cancel this out, the U-Joint angles between the transfer case and differential should be as close as possible during normal operating conditions. Also, make sure the U-Joints on the drive shaft are 180 degrees offset from each other. Otherwise, you will just magnify the speed difference instead of canceling it out (If that is at all possible to change...not sure).

Mark

Can you shim a coil-sprung axle? Wouldn't the shim have to match the shape of the perch, so best keep the spring situated?

That's an interesting idea, Bill. Wonder how that would work. Doesn't seem like it would it work. In my head, it would only change how the spring sits and the NOT the angle of the axle.

EDIT: Fixed my earlier post.

I am going to try to Tbar crank the front today (after I get her back from the exhaust shop). I hope that will fix most of the vibes

have you even put in the new uni's yet? T-bar crank isn't going to fix it. <img src="/forums/images/graemlins/shame.gif" alt="" />