Not sure what year but I've read many have had problems with the stock IBC. It can be locked out with a P3 if needed. Best EB in stock testing, about 180 hp of braking. Yes tow/haul to lock out overdrive.
The IBC came out, I think in 09.
The tow/haul does not lock out overdrive, it changes the shift points of the transmission, at lest that what it does on my 07.5 with the 6.7. Yes you will love the exhaust brake and it works best with T/H engaged.
Great E brake. Towing a 10K fiver with a 2011 3500, I rarely use the service brakes except when actually coming to a stop. OD not locked out in tow haul, mine will tow in 6th gear conditions permitting.
"Never trust a man who has not a single redeeming vice" WSC
I am very impressed with my 2010 Ram's EB and IBC. I've always had Tekonsha Prodigy controllers, but find the integrated one just as good for braking. Works just fine with my triple axles. It is nice because you don't get that initial lock up feeling and the late release after you let off the pedal like you do with some controllers. I really can't tell that the trailer is there because it integrates so well. As far as the EB, I love that thing. I always wanted to add one to my 2004, but never did. I don't ever want a truck without now. Hardly use the brake pedal as it works so well. My camper weighs 19,000 loaded and the entire truck and trailer weighed 28,000 when loaded up. It will pull the unit right down when decelerating and will hold it very well on 7% downgrades. I haven't been down anything steeper yet. I even use it without a trailer and it should save my brakes for a long time. I haul 15,000 pound of hay a lot with it on a flat bed and it is awesome.
2010 Dodge 3500 Mega Cab Cummins Diesel DRW
2009 GMC 2500HD D/A Crew Cab
2012 Dutchmen 3795 Voltage Epic Package
2012 Smart Passion for Two
2003 Suzuki Intruder 1500LC Cruiser AD USAF 1996-2011 1700+ hrs E-3B/C AWACS