SLAYfriknBODIES

I have a 93 pickup. Regular cab. Have a cobbled together 3" suspension lift. Ever since I installed it 8 months ago, I've been fighting driveshaft vibration. I solved it with a 4Crawler DS spacer, however it's only compounded my operating and pinion angle issues further. I'm now changing u joints every 6-8 months. They'll be fine for awhile, then around 40 mph in 4th gear I get the "afterburner" vibration. Soon it spreads to wider and wider speed ranges into 3rd and 5th gears.

I know that between a transfer case drop and rear axle shims you can lower the angles on those u joints to let them operate at or nearer to design angles.

Im looking for the factory driveshaft operating angle if anybody has that number on hand so I can break out the pocket calculator and start doing some maths to get my needed shim angle worked out etc.

Also looking for any useful pointers from anybody with experience solving this annoying crap!

Thanks guys.

osv

rear driveshaft?

it's long enough to where angles shouldn't be an issue.

regardless, the flanges that the driveshaft bolts up to have to be parallel, or you'll get vibration on deceleration.

one of these will tell you what the angles are:

http://www.harborfreight.com/dial-ga...der-34214.html

SLAYfriknBODIES

yes it's the rear driveshaft. Very clearly the angles are an issue. I've fixed vibrations back there before with spacers, new U joints and properly aligning the splines (Goodyear was 90° off and my driveshaft was all out of balance)

osv

splines being off could cause a phasing issue, and it would affect the balance, but none of that is relevant to driveshaft angles.

adding a transfer case shortens the shaft length, which definitely affects the angles, but since you didn't mention a second case, we assume that you have a factory length rear driveshaft.

your 3" lift shouldn't be an issue:

"So, for an example. on my '85 4Runner I found that with the stock rear driveshaft running at about a 12° operating angle (approx. 4" lift, 50" long shaft), I had smooth operation. But when the shaft was shortened about 6" (due to adding a 2nd transfer case), the operating angle hit about 15° and I found it no longer operated smoothly, even with ideal u-joint alignment and a professional balance job on the shaft. So by converting the top u-joint to a CV joint and re-aligning the pinion angle, the shaft did run smooth again."
http://www.4crawler.com/4x4/CheapTri...line-101.shtml

SLAYfriknBODIES

Hey thanks for the link!


I'm in the middle of a whole front end rebuild while I wait for funds for an SAS. The squealing control arm bushings was driving me mad.


I'll get to the driveshaft next and will start with having it balanced and replacing my U joints one more time. Possibly the dings and dents from various wheeling trips are throwing it out of balance and straining the U joints.