It happened twice and both times on rainy days.
 

I thought the first time was a fluke but it happened again today right when the rain started, the same as before.

I'm driving the car and everything is going fine but when it started to drizzle, very loud dead thud sounds started coming from the rear as though I had 2 flat tires. Every Small crack in the road resonated through the car. I also had to steer it with both hands because it felt as though it could jolt left or right at any minute.

What could this be?

This has only happened twice and both times were on rainy days and both times it began as soon as the rain started.

I'm sure I need the rear subframe bushings but I don't think that would make this kind of issue only in the rain.

Get your rear suspension checked!

Thank you but I'm hoping to get some insight from others who may have experienced or know of this issue before running off to the Indy shop. Many times these things can be repaired by myself or is something small like a bad connection on the fuse for the air suspension. But I really do appreciate the suggestion. :thumbup:

Well ghost is actually right. I think your control arm bushings are shot, the wet road, gives you enough loss of traction to unsettle your suspension. Time to really check the bushings. No fuse to pull.

Concur, bushings or the SLS in the back is slammed.

Yeah, I wasn't disagreeing with ghost suggestion to check the rear suspension, I kinda already knew the issue was in the rear suspension. I was looking for suggestions as to what areas to focus on or relating areas that may cause the issue.

I will take your suggestion and check the control arm bushings today. I already have plans to change the rear subframe bushings myself. :p:

What is the SLS?

Self Level Suspension The air bags might be leaking, the compressor might have missed a beat, let them slam and thats the thud

Ahhhh. I see. Thanks.

Ok, today it happened again and of course it was raining. Luckily I had my 20 mile drive from work to analyze what MAY be happening.

As I was driving on the freeway I wouldn't dare go above 40 mph. The rear end seemed liked I was driving on skis. The rear tires have plenty of thread but you would of thought I was driving in snow how much the rear end seemed to slide to the side.

When there was a line in the road that was parallel to the direction I was driving and my tires hit it, the car would shoot over.

The dead bumping sound didn't start until about 10 miles into the ride. And it would come and go.mwhen it was happening it sounded like I was riding on flat tires.
I think I know what was happening, let me know if this sounds plausible:

I believ it's the rear shocks. It seems as though when the rear shocks get wet they loose their ability to dampen the bumps from the road. I'm assuming the water/moisture breaks the seal long enough for the shocks to just slam up and down.
This would come and go during the last 10 miles. Sometimes it was perfect and others bam bam.

Although the ski like driving continued no matter what. Seems as though the rear alignment is so out of wack that the rear end slides into the direction of the angle they are misaligned.

Yesterday I did check all of the bushings in the rear and visually everything looked good. The rear driver side air bag was installed in May of 2012 and the plastic box with the plastic arm that I assume determines when to add air.