I have this vibration like the driveshaft is outta balance when I let off just a little bit at 60 or above. If I let off the gas all the way the drag on the drive line is enough to where I don't get it. But if I let off just a little to where things are relaxed (no load) I get a vib that sounds real nasty. I just fear for my pinion bearings or my transfercase rear bearings. I've been living with it cause I really don't drive highway that much. Oh and the drive shaft yokes are timed and in line with each other. I spacered the transfer crossmember down 3/4 of an inch also. Still no help. I'm just wondering if others with the same lift (I replaced the rear springs with s-lift spring packs)have the same problem.

How much for a new rear stock driveshaft all complete (U-joints and yokes installed ready to install)??

just from reading posts about lifts, its usually the altered pinion angle that causes the vibration, so even a new drive shaft is still going to have the same vibration

I hear ya on the pinion angle thing, I was wonderin if anyone in toyota land has heard of the superlift 5" lift spring packs giving this kind of vibration on short bed trucks like mine?? If it is a known common problem, whats the common general fix for it?

There are known driveshaft vibration problems with known vehicles with certain lifts. For example jeep TJ's or Older Chevy blazers with greater than 4" lifts on them. some go CV joints on rear driveshaft.

Measure the driveshaft/pinion angle and then install some shims to correct it.

Since you are getting vibes when letting of the gas, my guess is the pinion angle is a little too low. Pinion naturally tips up under load, but when you back off the gas and coast or decelerate, the pinion drops back down and vibrates. Could also be looseness in the pinion or t-case flanges, see if you can feel any play in either flanges.

my t-case flange for the rear d-shaft came loose and I had the same prob.

I went and checked it, its tight, it started right after I installed the superlift lift kit.

I think the culprit is the angle, like what was mentioned. I really don't like the idea of shims, but what am I suppose to do. Where do I get the shims??

Shims are available from the page I posted earlier (with the measuring instructions). You may already have some shims on there, many spring kits come with shims and you may or may not need the shims supplied. For example on a single cardan driveshaft, you normally need no shims when installing lift springs only, but you do need them with a CV (double cardan) driveshaft. Also, you may not need the t-case spacers I think you mentioned. Those spacers would tip the t-case flange down at a steeper angle while your problem sounds like the pinion flange is too low (i.e. its at a lower angle than the t-case flange), so you may just need to pull those spacers. Measure the angle difference and figure out how far its off and fix it.

Steel shims (like I make) can be bolted or welded on and since they are steel, they are much less likely to break like the low quality cast alumunum shims you often find. Other options are to cut and re-weld the spring perches on the axle in the proper orientation, or you could add a longer spring shackle to gain angle at the pinion flange.

4crawler, I have to run a couple of things past you first.

First when I installed the lift the vib was real bad (worse than it is now) I took loose drive shaft and made sure the yokes were timed, yokes in alignment, not off a little or 90 degrees out of sink of each other with a flat straight piece of wood.

So I installed some thick washers to bring down cross member about 3/4 to 1 inch and the problem was less severe. If I take those spacers out man you talk about some bad vib. noise. I agree that the front of the diff. needs to come up a few degrees.

Don't wanna use longer shackles, will get "back jacked up look" no good. What I was thinkin was to take out the "over load" leaf which is a thick piece (note I don't haul anything more than a cooler with beer/full size spare/little bit tools) and get some of your angled shims (with your recommendation to which ones I should get) and angle the front of the pinion up a few degrees. Can you help me out?? What do you think about the idea???

The t0case spacers lower the top end of the driveshaft, so that can help a bit. T-case flange normally points down a few degrees, the spacers also drop that angle a bit more. You could be at the point the shaft angle is too steep to ever run smooth. Mine hit that point somewhere between 12 and 15 degrees overall operating angle. Even with everything perfect (angles, phasing, balance) it would still vibrate.

But first, follow the instructions on my page, if you could not follow the link above, here it is directly.

In summary, tape measure across the top and bottom of the driveshaft, record the difference in flange-flange distances, every 1/16" off is 0.9 degrees. You want to end up with the bottom distance about 1/16" - 1/8" more than the top flange to flange distance.

I understand! Thanks for the help. Thats a real good thing to know (bottom flange to flange 1/16" -1/8" more than top flange to flange) will measure and take appropriate action to correct. Whether it be shim with "overload" out or longer shackle with "overload" out.