After installing my 5.5" Superlift, I was experiencing rear driveshaft vibration. This was being caused by the driveshaft being too short. There wasn't enough of the splined stub going into the tube, so it would wobble. For one, this is annoying, and two, it can be dangereous. If the driveshaft were to seperate, well, let's just say that wouldn't be good.
I had the driveshaft lengthened by almost 4", so good extension would be possible with still plenty holding the two together. Works like a charm. Cost me $250. Well worth it.
I have had no problems with the front driveshaft. Its length is adequate.
I personally don't think many people check to see if their drivehsaft is actually long enough, most only do something if something goes wrong.
On the same subject, keep in mind that when you do a lift, and possibly extend the driveshaft, make sure your pinion angle matches the transfer case angle. My spring perches on the 5.5" didn't set them accurately, so I had it set to match the transfer case angle. Also, make note that the spring perches supplied in the 5.5" kit are just clamped on with the springpack U-bolts. This is not very strong. I had mine welded to the axle after the correct angle was set. Springover setups in the rear have a tendency to wrap the axle about the spring. If the perches slide around the axle also, the pinion angle will be off, and something is going to break, U-joints, U-bolts, driveshaft, etc. If this happens, the whole rear axle can separate from the vehicle. It's not hard, weld the perches. All stock perches are welded to the axle.
Also, ACG78, since you're looking for about 6" of lift, why not go with the 5.5", instead of doing a 4" suspension lift and a 2" body lift. Sounds like more work. Plus, the body lift is where you will possibly have problems with steering and shifter length, also bumper realignment. The 5.5" works well.
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DOGMAN
91 4dr 5sp
5.5" Superlift
"Downhill is just uphill in the opposite direction"
