I purchased a certified pre-owned 2009 Mini Cooper convertible 3 months ago. When driving over bumps and especially when in a turn, the steering wheel jerks violently. When this occurs you must keep two hands firmly on the wheel to avoid losing control.

I brought the car to the service dept at the dealership and they said that everything looked fine and it is simply the way the car handled. They explained that the suspension on this vehicle is simply stiff...I have driven a number of other mini coopers and have never experienced this issue. There is most defiantly more than "stiff suspension" in this case.

Any thoughts would be greatly appreciated.

Had something similar happen shortly after I bought my 2004 MCS back in march of 2008. Turned out to be a lower control arm issue, redone under warranty. However, the MCS (can't speak for non S) does tend to track ruts in the road to the point of having to hold on with both hands. This should only happen on certain roads, not all the time on every road. If you notice this on certain roads, should'nt be a problem. Also check if your tire tread is wearing out in a strange pattern. That could point to a steering/suspension issue, like mine had.

Mine did the same thing, 05 MCS the car had run flats and they were new, it was very scary to the point that the car went over to the next lane, I changed to non run flats and the issue was gone, my lower control bushings were new at the time the alignment was off when I took off the tires. I don't know if you have run flats but that could be the issue if the LCA bushings are ok if you are near a MINi specialist I would go there for a second opinion, the dealer told me the same thing they told you when I asked.

Tie rod ends are gone, take it to a wheel alignment shop, pretend you want to get it aligned and ask the guy to check the rod ends first before doing any work.

What wheels and tires?
How many miles on the car?
Does it have sports suspension package?

Given that it is only ~3 years old, and assuming no accident damage, I would point the finger on usual FWD bump-steer amplified by the stupid-stiff RFT tires. Changing to real tires (non-RFT) will help a good bit.
Beyond that - if you can't handle FWD bump-steer, you might have to go back to RWD cars

a

I took my MCS hatch in for detailing yesterday and the loaner car I got was an '05 MC vert. I immediately experienced the wheel pulling violently left or right when going over bumps in the road. The loaner car only had 37k.

When I returned the car, I mentioned it to the dealer. He said "Oh yeah, that's normal with the base Minis."

On my car it was the Run flats I wonder what the OP has on his/her car Runflats or not

I agree, I wouldn't get a NEW transmission. The problem sounds like a bad valve body. You can get remanufactured units for about $700 (last I checked). They're pretty easy to install, but will require new fluid (reuse the filter). You can try adjusting the valves first, but that again requires the pan to be dropped, which is quite a big job since the lower cross member must be removed in most cases. If you have the money, try a new vb. You only really need a full rebuild or new trans if your gears are slipping, which is like a slipping clutch: you're in gear and are accelerating, but the RPMs go up faster than your acceleration. Bad valve body is you're not in gear and it's as if you have the clutch in. You press on the pedal and your car only slows down, like the engine is not connected at all to the wheels.