Help! I lifted my truck with a 2" OME kit about a year ago. It was more like a 4" lift given all the sag in the stock suspension but it looks good. It did give me some driveline vibrations which were worked out by shimming the transfer case down... or so I thought.

Now the vibration is back. It's more like a shudder around 25-30 mph /40-50 km/hr and then goes away mostly until it comes back around 50-60 mph / 80-100 km/hr. The manual hubs are usually unlocked. I pulled the driveshaft and checked that the angles for the drivshaft flanges are the same. The drive shaft was rebuilt and re-installed and I even drove it without a rear driveshaft in 4WD at highway speed. No difference.

It shook with two different sets of tires but I'm taking it in to get the current set (225/75 R15 snows on Toyota steel rims) checked for balance and run-out. I usually run 235/75 R15 Desert Dueler ATs on the factory aluminum rims. The whole body of the truck shakes and you feel it in your feet mostly. There's no real shake in the steering wheel or the gearshift. The shake is more pronounced when accelerating or decelerating at the problem speeds and it varies with speed, not engine RPM, as I tried the same speeds in different gears.

I'm stumped. Any ideas would be appreciated...

Thanks!
Sean.

Check for proper driveshaft phasing:
- http://www.4crawler.com/4x4/CheapTricks/Driveline-101.shtml#Phasing

and if that is OK, check the alignment:
- http://www.4crawler.com/4x4/ForSale/Shims.shtml#FAQ1

Thanks, I'll check the driveshaft phasing. I already checked the alignment and found both the T-case output flange and rear axle pinion flange are parallel, about 4 degrees off vertical. The only problem is that it still shook without the rear drive shaft.

If the shaking is present with the driveshaft removed, then you should look to the rear axle or wheels/tires themselves. Could be tire imbalance or out of round, wheel bent or out of round, or a bent axle shaft.

Thanks, again. I wouldn't expect a tire balance problem to show up at such a low speed as 25-30 mph but I'll get them all checked out.

I have seen tires shake at slow speeds like that when they were having cord separation. You very well might have a bad tire which could be close to failure. checking it out soon would not be a bad idea.

Frank

wheel balance can will mostly happen at higher speeds at 50mph and above especially on the freeway. If it has wobble at lower speeds could be tire seperation or bent wheel. Check tires and wheels first then start digging deeper.

Thanks! Tires will get checked on Friday. Driveshaft phasing is correct so my next thought is a rear axle bearing. They were done at 300,000 km and I'm at 444,000 now. The rear has been a bit noisy for a while. They should be able to check them when the wheels are off.

Well, the tires checked out. The worst one was off by 1/2 ounce and all are round. The mechanic also said he thinks the wheel bearings are okay.

The virbration is still there and no better so I'm going to book some time on a chassis dyno with vibration monitoring. Does anyone have any other ideas?

Thanks!

I found my problems by simply putting the rear axle up on jack stands. Let the engine idle in ~2nd gear and use a pointer on the spinning wheel/tire to check for out of round. Starting at the tread, work in to the wheel and then the hub checking for any wobble.