I'll Take No. 6 Please
I thought it might be helpful to others to relate my recent transmission reprogramming experience for anyone with an Allison B-400. I know there are some MCI guys that have swapped Series 50's and Allison B-400 transmissions into their bus.
My bus has the Allison B-400 transmission. It operated it's whole transit life as a 5 speed, which the majority of transit systems seem to spec. This was just fine, as tansit buses typically don't do much high speed travelling. Even without a 6th gear, it easily hit 62 mph, which is where the road speed was set in the engine computer. After it was retired three years ago, I also operated it as a 5 speed, although it wasn't operated very much as the conversion was in full swing.
That was until two months ago. You see, the B-400 is really a six speed transmission. I can't remember all the ratios for every gear, but 6th gear in my transmission is shown to have an over drive ratio of .67 to 1 by my owners manual. That's quite an over drive. It does wonders to counter my 5.38 ratio rear end.
About two months ago I contacted my local Allison dealer and inquired about getting 6th gear activated. This is controlled electronically by the transmission computer and only requires reprogramming the computer. Allison was willing to do it, but only with an authorization letter from the manufacturer. It was explained to me that this was to protect themselves (and me) from over speeding drive train components and causing an accident. Apparently, there are some manufactueres that do not have components capable of handling the increased rpm they would experience.
I contacted my bus manufacturer, Gillig, in Hayward California. I was directed to their engineering department and was helped most graciously by one of their staff. Upon explaining the original owner, Volusia County Transit (aka Daytona Beach), no longer owns the bus and that it is used privately by myself, they kindly agreed to send me a letter authorizing Allison to reprogram the computer and activate 6th gear.
I received the letter electronically as an email attachment. The next day I took the letter to Allison, along with a spare transmission computer I have, and in a couple of days picked up my reprogrammed computer. While they were at it, I asked them to tweak the mode settings as well. The computer has two modes, economy and performance. Now, the default mode is economy (per my request) as I'm much more interested in better fuel economy than performance. I can easily switch it to performance by simply pressing the mode button on the fly. The difference between the two is the rpm where shifting occurs under full throttle.
Installing a WTEC III computer is a snap. There are three connectors that plug into the computer and you're done. After installing the reprogrammed computer, I took the bus out for a test drive and it performed beautifully. I haven't operated it enough to see how it affects fuel mileage yet, but I hope to soon. I'm hoping it'll give me at least one more mpg. Now at 65 mph, the engine is puttering along at a noticably slower rpm. I think I'll really like this change.
There's not much visually to see on this mod, other than the reprogramming sticker Allison put on my computer. The technician that did the programming added a bit of humor by what he named it. That's fine by me ---- we can all use a chuckle.
