I have a 2001 SE and I am experiencing VERY bizarre problems from the rear suspension. All of a sudden when I put the car into reverse I can maybe travel 5 feet and then it starts grinding and clunking and the left rear side of the vehicle jacks up several inches and the car grinds like hell. It feels EXACTLY like Im running over something. Its pretty nuts. Any idea what in the world this is? The car has 80k on the odo.

Part of your description sounds like a problem with the Automatic Leveling Control sensor is bad. That will cause the air pump to fully pressurize the shocks, but it should do it to both of them, not just one. Also, the pump should not causing a grinding sound. You may have several issues going on if so.

Here'* a link to information on the sensor. You can try disconnecting it, and see if the problem goes away.
Automatic Level Control Sensor Replacement

It doesn't really seem to be the load leveling system. What it feels more like is that as I back up something is soooo loose that its bending and twisting upward. Its definitely not rising because of a pump, its rising because its binding itself up. As soon as I pull forward a foot or so its all ok. It literally feels like I'm backing over something and hitting a wall it clunks that hard. I've read on here about the shock mounts, could that be it?

I hope I'm not telling you something you don't already know, but...DO NOT drive that car until you find out what'* up and fix it..

Sounds to me like something'* broken in your left rear suspension. Unless someone chimes in with something more specific, I'd say put some jackstands or blocks under the rear frame (for your safety), get under there with a flashlight and compare left and right side suspension parts to see if something looks broken or out-of-position.

I'm with ^^^^ that guy. Support the car properly and do a thorough inspection. If it is not the shocks, then it is likely you have some type of serious issue. Even a frozen caliper on one side shouldn't cause that kind of problem.

The shocks do not support the weight of the vehicle like a strut does, so the mounts would not likely be a cause here. They cause quite a clunking noise when going over sharp bumps.

Hmmm, now that you mention frozen caliper.. the brakes are maybe a month or so old, all around. The last few days they've been making a hellacious noise, not really a grinding, but like a high pitch humming during decelleration.

I also have a post on here about what I think may be the BCM. I have no turn signals, cruise control, or tach/speedo readouts at all. The Systems Monitor also says "TIRE PRESS" but nothing is low. Heres a link to that post: http://bonnevilleclub.com/forum/view...748&highlight=

Starting to realllllyyyy make me regret my purchase of a Bonneville :( And I loooove the car so much!

Anyone think it could be locked up calipers? It sorta seems like it breaks free when I continue backing up, but it scares me, lol.

I dont know what the problem is but dont drive it until you do. Also add your car description in your signature it helps for posts you'll be making in the future. Go to profile to find it

I'll refer back to what agrazela and Archon said, and recommend that you jack the car up as said. Until you actually take a look back there, we can shoot all the possibilities we want at you and you will still be none the wiser as to the actual problem.

Even if it turns out that you have severe caliper locking issue, it will help to have the rear end up in the air to find out.

While we are on the subject of seizing calipers, and while you have that car up in the air, take a good look at the brake hose leading to that right rear wheel. Sometimes, after a brake job the hose will collapse, causing brake seizing.

Another thing comes to mind. Do you use the emergency brake, and could this happen either after rain, or a car wash? If so, the brake pad will often stick to the rotor when things dry out. It can make quite a snap as it lets go, and you may feel just a slight rise to the rear while backing. You'll also hear some light grinding the first stop or two until the rust is removed from the rotors.

Or, quit backing over the kids bikes.