Just bout a 87' sammy that the previous owner had just put a 2 1/2" spring lift on. This is still spring under. When I drove it I found it had a death wobble around 40 mph. I installed a 4" drop pitman arm, and it appeared to have solved the problem. I towed the sammy home with a tow bar, and a few days later was driving it when I hit a small bump on the road doing about 50 mph, and the wobble reappeared. Where should I start? A friend is telling me if I just go with a high steer then it will take care of the problem. I'm not sure about that though. Hope ya'll can give me some advice.

Start with the simple things...
tire pressue
tie rod ends
shocks
loose u bolts / shackle bolts
bad / worn / unbalenced tires
bad rim

To add to the simple list:
Looseness or play in the: steering box, rag ,or U-joint (assistant: turn steering wheel back/forth and examine every connection).
Front end alignment.
Wheel bearings (easily test tie-rod and bearings by trying to rock the tire up/down and left/right while jacked in the air).
Shackle lifts can be contributing.

My 87' on 31 TSL with 3" Calmini lift springs (spring under still) had wobble(s) I ended up doing the following for one reason or another:
Replace wheel bearings (did entire front end actually).
OTT complete high steer.
Installed aftermarket bump steer shock to replace tiny stock unit.
Already had 3" drop pitman.
Adjusted/tightend steering box (this fixed the majority of my wobble).
Heavy duty axle U-bolts. I had a few nuts on my stockers that kept loosening up on their own.  This should ensure my axles dont move around.  New units are much more meaty and I think they are grade 8.

Good luck and let us know what you find!

steering stabilizer? (dampener)

Just an Idea....
Had A 66 Ford F-100 that if you hit a "Tar Strip" on the freeway.....
Get ready, you are changing lanes !!!!!
It turned out the the bolts mounting the steering box to the frame were loose !!

CAPT

I've dealt with the death wobble twice and have a suspension similar to yours with 30" tires.
The first time the wobble came it started at 40+mph. I solved the wobble by replacing the king pin bearings and repacking the wheel bearings.
The secant time the wobble came at any speed after any suspension undulation. I found that the steering stabilizer's bracket at the pit man arm had sheered off. I replaced the steering stabilizer with a much much better one and a little fabrication.

Your stabilizer might be a simple fix but the problem is still there. Your stabilizer perpose is to help smooth out those OMG highway potholes that jump out to grab ya. It's not meant fix any evils that may be underlying. I would look deeper that the stabilizer.... it might help you but it's not your problem...
 

Along with all the standard maintenance items above - I would check into the steering and driveline angles....

Ive done quite a bit of lift kits over the years - including a 1 ton conversion on a 71 GMC with 12" of lift and if you get death wobble after a lift kit is installed then you can assume something got missed or skipped, or changed up the alignment or angles

If the downward degree angle of the driveshaft from the transfer case doesnt closely match the upward degree angle from the pinion then your gonna get some bad vibes for sure..

I bet if you get your caster checked its gonna be off

did you get any mud on the back side of the rims?