Unlocking 6th Gear for Allison 2500 Transmission, Is It Worth It?
After researching on this forum and the internet about the locked 6th gear in the Allison transmission, I'm curious as to why this is so important. I understand that it'll create a double overdrive and will drop the RPM's on the engine, but how much will this help a bus in true numbers? Has anyone done it and seen a substantial increase in MPG or lower RPM's? I'm not going to pretend I know much about buses, but I'm trying to learn and would appreciate real world information if it's available.
I ask because I have a 2007 IC with a 2500 Allison that can be unlocked. We intend to use our bus as a family vehicle and will be travelling from Waco, TX to Houston, TX every few months to take our boys to see specialists for their medical condition. Right now on short 30 mile trips I've taken to get used to driving the bus, I see that I'll probably be running at a top speed of 65 at around 2400 RPM, or most probably 62 at 2200ish RPM. The bus can get to 70, but it won't hold the speed when I set the cruise, but 65 or below is easy for it. I do know my bus has a 5.29 rear end. I'm not looking to get there fast, but anything I can do to squeeze out some fuel efficiency is what I'm hoping for.
After getting off the phone with the dealer who is currently working on some things for me, he said the cost would come to roughly $1K to $1200 by the time Navistar does their portion and Allison does theirs with the reprogramming. I've read about some of you paying a 3rd party $350 to unlock the gear, but using real dollars and cents, how quickly did you recoup the cost? And more importantly, has it truly been worth the investment; not in theory, but in tangible figures?