Caster and u-joint vibration

For starters...... 94 2dr XJ with a measured 6" of lift fore and aft. RE upper and lower adjustable control arms, adjustable trackbar, and 2 degree offset balljoints in the top of the knuckles.

Factory spec says 5 to 9 degrees. The rack (Hunter 300) measured 5.48 degrees on the left, and 5.74 degrees on the right. Toe-in was 0.11 degrees. Not bad considering that it's gotten new springs, new tires and a new trackbar assembly since I put an angle finder on it!

Here's the rub: the operating angle at the axle end u-joint of the front driveshaft is a little excessive, the Mark I eyeball figures somewhere above 5 degrees, and yes, it's making vibes.

Opinions wanted. What would you do? Reduce caster a couple of degrees to reduce the operating angle? Live with the vibes? Do something else?

I'd play with reducing caster in small increments until the vibes appear to go away. Keep an eye on how much you reduce as that will affect your steering (more "squirrely"). On my 6" lift, I'm running about 5.1 degrees without vibes, and I have a "good feel" to my steering.

Letting it continuing to produce vibes will only accelerate the wear on your u-joints and play havoc on your tcase...

Ivan

Kind of where I was leaning....... vibes != good.

ChiXJeff said:

Kind of where I was leaning....... vibes != good.

Click to expand...

Only other option would be cut and rotate the knuckles OR dual cv front driveline. Not too many driveline shops that will recommend the latter.

I've been seriously considering cutting off my knuckles and re-welding them with an extra few degrees of caster. I'm running a similar setup to the one described above.

Who has successfully done this?

JEEPZZ said:

Only other option would be cut and rotate the knuckles OR dual cv front driveline. Not too many driveline shops that will recommend the latter.

Click to expand...

The problem with dual CV joints is the problem with slop magnification.

And if I'm gonna turn the yokes, it's sure not going to be on a D30.

More data......

Upon closer inspection, there is a little slop in the slip shaft on the front driveshaft. I didn't have time tonight, but I think I'm going to pull the front driveshaft out by the weekend for a quick test.

I also have a front axleshaft u-joint to replace, it's just started to wiggle.

Another 'no so inexpensive' solution is a manual hub conversion.

or use a disco axle.

Gary E said:

or use a disco axle.

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Disco D30's rock! Vibe free at 80mph and 2Low too......

Yet more data.....

Last week, I was in for the emissions check. Rode in the passenger seat on the rollers, up to 57mph. No vibes to speak of.

Finally pulled the front d/s tonight. Guess it's time for a new driveshaft, the slip is shot.