</font><blockquote><font size="1" face="Verdana, Arial">quote:</font><hr /><font size="2" face="Verdana, Arial">Originally posted by osburn:
<strong> </font><blockquote><font size="1" face="Verdana, Arial">quote:</font><hr /><font size="2" face="Verdana, Arial">Originally posted by 4wheeler4CJ:
With all due respect, why can't you drop the TC without shimming the rear axle, or vice-versa? They are a "cumulative" effect, no?
Dropping the TC lessens your angles, as does shimming the rear-end. Whether you do one, the other, or a combination of both, anything will help the driveline angles.</strong></font><hr /></blockquote><font size="2" face="Verdana, Arial">When you run a standard driveshaft (ie one u-joint at each end) the angle of these two u-joints must be parallel. By dropping the tcase, you're changing the angle of the upper joint. You must change the angle of the pinion joint to compensate for the change you made on the tcase output. So if you do one, you must do the other. That's why this fellow is suffering from vibrations. Based on his lift, I don't think he needs to drop his tcase. That's what I'd try first anyway. If he still has vibrations, then lower the tcase back down and shim the rear axle pinion up 2.5 degrees.
This rule does not apply when you run a CV driveshaft. The two joints in the CV counter each other so the joint on the pinion must be zero. Or actually, it's best in practice if you set the lower joint to be about 2 degrees shy of zero.</strong></font><hr /></blockquote><font size="2" face="Verdana, Arial">Where the heck did you get that info? I did a 2.5" suspension lift, did not shim my rear axle, then lowered my TC a good inch or more, and never had vibes. The U-Joints do not require to be at the same exact angle on each end, there's no way to justify that reasoning.
A TC case drop will better your vibes. If it doesn't solve it, then you have to look elsewhere, but that doesn't mean that dropping the TC case caused it or worsened it, LOL!