steering wobble and seat vibration (not at the same time)

I know these can be a nightmare to troubleshoot, but....
Got the steering wheel shimmy, had it when I bought it used.
2008 4x4, has 3" spacer lift and 1" wheel spacers on the front. LT 285 75R 16 tires. Newer Toyota alloy wheels.
I thought I had my trouble isolated to incorrect wheel spacers (it had lug centric with factory wheels, no good). I just installed 1" hub centric spacers, no change. New brake rotors, no change.
Here's what I've noticed that confuses me.....the shimmy comes and goes, sometimes the steering wheel wobbles slightly at 35-40, sometimes it doesn't. Sometimes the shimmy is bad at 50-55 mph, get to 60, back off and doesn't shimmy at 50 any longer. Maintain 50 and shimmy comes back. Sometimes the steering wobble (shimmy) goes away and I feel it in the seat bottom, then that fades and back to steering wobble.
Really odd, how it seems to be seat bottom or steering wobble, but not really both at the same time.
I've checked front end, all tight bearings, tie rod ends, ball joints.
I've had out-of-balance tires on other vehicles and they did not act like this, the vibration was very predictable at certain speeds. This seems to change, making me think it's driveline related.
Anyone have this exact symptom on their Tacoma?

 

Front: Check your driver side needle bearing, could be time for the ECGS bushing mod. And start considering an actual lift - not for vibes but because a 3" spacer lift sucks donkey balls.

Rear: Grease your driveline joints, check torque on the U bolts for the leaf pack, inspect your carrier bearing.

Both: Check tire balance and make sure the mating surface on the wheel and on the brake side are clean and free of things that would cause them to mount cockeyed. Sounds silly but can have a big impact. I've re-balanced my tires from time to time when I start to get the wobbles after a wheeling trip and instantly it goes away. Might need to get them road force balanced.

 

How old are your shocks and springs. I had these symptoms on a first gen and it turned out to be worn springs.

 

I don’t have a spacer lift. I have 5100’s, coils and aal’s

I did have wheel bobble and vibes though. The vibes were so bad when I didn’t have a passenger riding with me the passenger seat back and head rest would bounce around severely. Could feel the vibes in the floor, steering wheel and seats themselves.

Spent countless hours reading threads on here. Addressed all the common fixes and nothing ever seemed to remedy it. Gave up and figured maybe it’s just select tacomas because other have gone through the same process with no fix.

Ended up getting new rims and tires. No more vibes.

Went through two sets of tires so idk if I had a bad rim or if both sets of tires I had were shit. Forgot what it felt like to ride in a vehicle that didn’t try to shake itself apart.

 

have you checked the steering column rag joint bushing? do a search on here for zip tie mod or something...

 

Thanks for all the replies...I've checked just about all that was suggested, nothing found. However, once removed, I did notice the front tires are a little more scalloped than I could see while they were on the truck.
May just swap front to rear and see what happens. I WILL post my results (but it won't be until this weekend when I swap them around).
Thanks for all the replies!

 

Ok, here's what I've found - it ain't the tires. It's apparently the needle bearing at the front diff left driveshaft, as wi_taco mentioned. That cv shaft moves up and down WAY more than it should. I had ordered the ECGS bushing and removal tool in advance, just got it. Will be swapping that bearing tomorrow.
I also noticed that cv shaft has been replaced with aftermarket (doesn't have the notches). Wondering about removal, pry bar between diff and axle? Or, do I need to go and buy a slide hammer?
I also saw a video where the guy didn't disconnect the outer tie rod end, is that possible to remove the axle shaft with only removing the stabilizer bar loink, ball joint bolts and axle nut, then swinging the assy out of the way?
Thanks! Hoping this is an uneventful repair.

 

Update - haven't driven the truck yet, but I did complete the ECGS bushing and new axle job. Wasn't difficult, except the castle nut that comes with the aftermarket cv axle didn't line up with the hole in the shaft when torque was anywhere near the required 173 ft lbs. My choices were to loosen the nut (a lot), tighten the nut (a lot), or replace with OEM Toyota nut, cap and cotter pin.
I replaced with OEM Toyota axle nut, cap and cotter pin.
BTW, I was very impressed with the technical support from East Coast Gear, they were quick to answer any questions I had and they were very knowledgeable.
Only issue was that I could not find my seal/race driver set. Had to get the job done, ended up using a socket to hammer the bushing flush. My advice - buy the ECGS installation tool.
Anyone use a socket or similar to drive the bushing in?
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