I've owned my 2007 GL450 for over 10 years and have put 225,000 miles on it. The steering became more difficult a couple of years ago and I was getting a clunking sound over bumps. It turned out to be the mounting point bushings for the rack to the sub frame. Long story short I had the rack along with the power steering pump replaced as it all was getting old. Generally, the steering feels good now except for when the vehicle is cold. When I start it cold, the steering is quite difficult. But I've found that if I turn the vehicle off and on again, it often steers with minimum effort and feels totally normal. Any ideas on the cause of this? Thanks.