I've had the same issue with my 2007 3500. It's in the shop as we speak, for the 6th transmission rebuild. It keeps breaking the snap rings in 5th and 6th gear. I tow a 43' gooseneck everyday (when it's not in the shop!), and everytime it has done it, I was loaded with loads around 10,000 pounds or more. First time it did it, it wouldn't shift past 4th gear. I could pull over on the side of the road, shut the engine off and let it sit for a few seconds, and then restart it. It did fine for a few days after that, leading me to believe it was a computer issue. I went through this same scenario for about a month, because the dealership couldn't locate the problem. It finally broke the snap rings at about 93,000 miles, and the dealership diagnosed it. After 2 more broken snap rings, and Dodge paying to have the trans rebuilt, the next time it broke not only the snap rings, but the shaft between 5th and 6th gear. By then I was getting aggravated, and when I picked it up from the dealership last Thursday, they assured me that the issue was resolved. 3 days later, on Sunday, with about 19,000 lbs of drill pipe on the trailer, it did the same thing. Wouldn't shift past 4th gear after a hard shudder. Called the service department manager at home on Sunday night to voice my displeasure, and he said drop it at the shop and they'd look at it AGAIN! They still haven't diagnosed the problem, but they are putting an upgrade kit from Suncoast in the trans to "beef it up", and added that the next time it happens, it coming out of my back pocket. I need some help! It would be greatly appreciated. I have deleted the entire stock exhaust and dpf, with a dpf delete kit from BADP, as well as the egr bullcrap from under the hood (with a set of block-off plates from Shibbyutman). The only other modification to the truck is an S&B air filter and intake. Is it possible that removing the stock exhaust and dpf has generated more horsepower and torque than this transmission is capable of handling? Help!!!!