i am new to this forum, and so far i think it is great! I have just completed a spring over lift on an 88 samy, it included, 2 inch longer shackles, drop pitman arm, z link, spring over, new 1.5 in springs, new shocks, if my calculations are correct, this gives me about 6.5 inches of lift over stock. i put in 1.5 inch driveshaft spacers and now when i drive as i increase speed i am feeling a nasty vibration in the driveline, and kinda of a sound that is like poor gear mesh. to me it seems like the drive shaft is not at a good angle for the u joint to articulate. is it possible that i need more or less spacer in the drive shaft connection, looking for ideas, thanks for any infor. in advance

1st i would contact the manufacture. In some cases this is how they learn. Sure your not the only one to have this cond.

When going spring over axle and you went beyond the 6" rule on lifts. When the rear spring perches are welded on the axle is generaly kicked up no more then 20 degrees to help take care of the u joints binding. This condition only gets worse when you wheel it.

Even after the repositioning of the rear axle there may be a need to relief cut the u joints so they not bind under extreme wheeling. You may have to relieve the front u joints as well.

Depending on which springs you used there will also be spring wrap in the back and you may have to address this as well.

Welcome! I dont know how you use your rig or how you wheel but here is my .02

With axle wrap... which you most-definitely cannot ignore if you want your u-joints to last (along with your pinion bearings)... keep in mind that a ds spacer actually increases the angle of the drive shaft.  A longer shaft is the more costly but better solution.  I cut/extended mine but i drive very little on pavement or at highway speeds.

I now lock-tite all of my driveline bolts to each flange.  The plastic washered type nuts loosened several times for me and even lock washers did the same. Before i braced my rear axle (to avoid wrap) I lost a rear u-joint while driving.

I can just about bet that ur on the road to a failed u-joint or a dropped driveshaft so i would def. check all of them before u wheel again.  Flex your suspension on jacks/stands at the house and see how your u-joints look for binding. Take off the extended shackles and go from there if your binding.  Shackles lifts change your front axle (steering) angle... not a good trade-off with a mere 1" of actual lift. That should put you back under the 6" rule if your math is right.

Report back!