My 2005 MDX would vibrate/shudder/grind while accelerating between 35 to 40 mph. When I took it into the dealer, I was told they could not reproduce the problem. I had 30,000 miles on the car and was in the last month of my warranty. The noise continued to become more frequent and more noticable. I took it back 12 months after my warranty expired and presented hundreds of reports of the exact same problem taken from the internet. I also presented a service bulletin from Acura (06-003 dated June 9,2007) for model years 2003 & 2004. After opening a case with Honda America, many calls and many threats, I finally got them to agree to 100% coverage of a torque converter replacement ($2,000). From my research, I have found hundreds of reported cases of this exact same problem for model years 2002 through 2007 for both Honda Pilots and Acura MDS's. FYI
Transmission Problems - Torque Converter Shudder/Grinding/Vibration on 2005 Acura MDX
There is actually a recall for a programming upgrade which may help you with this problem if you are still having it.
Thanks for the tip. It actually turned out that the torque converter needed to be replaced. Even thought the MDX was out of warranty, Acura replaced the converter at no charge due the the significant number of torque converter failures in the 2005 MDX's. Thanks....