A few days ago, my car started steering wildly and swaying back and forth. It seemed that the faster I got, the harder it was to stay on the road.

Took it to the mechanic, he said I need new shocks. Bought 4 new shocks, replaced them, drove it, and the issue was still there.

Took it back, they said it was badly out of alignment. Had them rebalance my tires and realign all 4 wheels. drove it, the issue was still there.

Then they said my steering box was bad. That I was supposed to have 1 1/2in of sway in it, and I had 4 1/2. Replaced that, drove it, still had issues.

Took it in, got 4 new tires. Drove it, still had the issue.

On my way back from getting the tires, I decided to pop it in 4wd and see if that did anything.

4wd drive seemed to alleviate many of the symptoms (as far as the steering issue is concerned), but every rotation of the rear shell causes a pop thump noise, and the car would hop a small bit.

That made me think that maybe my rear axle was floating and causing the issue, but dropping it into 4wd would lock it and keep it from swaying.

Took it to the mechanic and he said the axle was fine and that he still couldn't figure anything out.

I've already dropped $1200 in parts over the last 2 weeks, don't really want to keep guessing.

Any ideas on what it could be?

2001 Blazer 2dr 4wd 4.3L V6

 

Several things can cause what you're describing, including what they've already replaced! Other possibilities are ball joints, idler arm, pitman arm, control arm bushings, tie rod ends, sway bar end links, etc etc. If the problem is as bad as you say, and the "mechanic" can't figure it out, take it to someone that knows what they're doing, (instead of guessing at your expense) and have them check everything for you. A well known, reputable alignment shop would be a good place to start looking. BTW, don't let anyone sell you a 4 wheel alignment on your Blazer, only the fronts are adjustable

 

Only time I ever had that issue, a rear sway bar link broke and because I had one bad shock, the back would swerve every time I hit any kind of bump.
Should say it pointed out I had a bad shock by breaking BECAUSE I had a bad shock.

I would agree it looks like you have something floating. Try to discern if it starts in back or is in front. Bad upper arm bushings COULD cause something similar but should react when braking v accelerating. in a slight turn

I agree wit der captain.. your mechanic is suspension incompetent. Why do I suspect he never drove the car.. and if he did he's even dumber than we thought.

Just had a thought.
Jack the back up, disconnect one sway link and set it back down. look at ride height each side
Then do the same for front besides checking the UCA and LCA for that matter, bushings.

I'm thinking bad rear spring.

 

Good advice so far.

I've got a mechanic coming by tomorrow to check it out, so hopefully these ideas will give us a good frame of reference.

Any other ideas?