Our first conversion...

[cadillackid]

seems like I need to go buy a bunch of Gen2 TCM's ,write a 6th gear tune to them and offer trade-ins for skoolie members.. what a PITA.. for a bus you own that is obviously out of service..

75 MPH is the typical limit max.. which consequently is what 99% of the truck tires are rated at as max-speed.. even though I get Blasted by on highway road-trips by the likes of 'Barons bus" running 80+ down I-75.... along with those Prevost campers with Big kitty engines.. not sure how they get away with it.. unless there are 85 MPH 11R22.5 tires out there I havent seen before..

-Christopher

[AJH3212]

You're 100 percent spot on about those high speeds exceeding the limits of the tires, my goal is to drop the rpm at cruise, less strain on everything, lower the fuel consumption.

[AJH3212]

Originally Posted by AJH3212

Here is the update. Looking at the world through Allison's glasses, the OEM manufacturer of the bus is their customer and at their request the sixth gear was locked out for safety reasons when the bus was built so; 1) the bus would not be able to exceed speeds any school district would be driving and 2) the top speed of the bus would not exceed the speed rating of the tires.

To unlock the transmission Allison requires a letter from the OEM of the bus (not a dealer) stating that they approve of the change with the VIN number of the bus and the VIN of the transmission. Allison will then issue a "Service Information letter" the last page of which is a release you sign holding them harmless against any liability if your bus breaks the land speed record. I have signed that release, paid them the $500 and have a technical service representative coming to the bus next Monday morning and we're done.
I hope this is helpful, lot's of paperwork, I'll report back with RPM and MPH in 5th and the newfound 6th speed next week.

Success. I drove the bus home this week, sixth gear is now available. The delta from 5th to 6th is 300 RPM. At 55 mph in 5th it runs 1900 RPM, in 6th drops to 1600 RPM same difference at 65 (2200 vs 1900). Speed limiter was set a the factory at 65 it comes off next week, I would like to cruise at 70 just to keep with most of the flow of normal traffic. I hope this is helpful.

[cadillackid]

now THATS some fantastic news to get 6th gear!! I know in my bus that low RPM cruise is really nice.. 1550 at 65 MPH is perhaps a little low.. but I set it so the least bit of lugging drops me to 5th which runs me back up to that 1800 or so range. your bus will probably run cooler and more efficient too!.. 1900 is a great place to run it.
-Christopher

[Rusty]

300 Rippem's?

I REALLY need to get my MD3060 unlocked now. Glide along in that power band.


(for my motor)

[AJH3212]

Having all six gear available was very important to me, the thought of driving across Wyoming or Montana in anything other that the most efficient gear would be the proverbial itch you couldn't scratch, torture. Don't need to go a million miles an hour, just what is just, proper and safe. I'm interested to see how the bus drives with the engine limits removed (Tuesday), results to follow.

[EastCoastCB]

Originally Posted by AJH3212

Having all six gear available was very important to me, the thought of driving across Wyoming or Montana in anything other that the most efficient gear would be the proverbial itch you couldn't scratch, torture. Don't need to go a million miles an hour, just what is just, proper and safe. I'm interested to see how the bus drives with the engine limits removed (Tuesday), results to follow.

Meh, folks do it with 7.3's and 545's. lol
But yeah, more gears is more better!

[AJH3212]

Speed limit raised to 80 by the MBE tech service rep, what a difference, 70 MPH is now well into sixth gear. 2100 RPM = 70 mph.