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Old 08-15-2021, 12:03 PM   #1
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Join Date: Dec 2020
Location: Kansas
Posts: 1
Year: 2005
Chassis: 35’ Thomas Saf-T-Liner HDX
Engine: Rear engine Cat C7
Cat C7 with Allison trans - 2005 Thomas Saf-T-Liner

We have a 2005 Thomas Saf-T-Liner HDX

As a school bus, it has 6th gear locked out

The Bus dealer we bought it from said a Cat dealer should be able to reprogram it to unlock 6th gear.

After a few calls, it doesn’t appear they’re all too excited about doing it and even want a lot of money just to run the numbers so see if they can get permission.

Our question - anyone have any luck using a TCM for a 6-speed out of a truck? If we swap out the TCM for the transmission then we shouldn’t need the reprogramming. Is that correct? Any thoughts or experiences?

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Old 09-13-2021, 12:21 AM   #2
Mini-Skoolie
 
Join Date: Aug 2021
Location: Santa Fe
Posts: 12
Year: 2007
Coachwork: Thomas
Chassis: HDX
Engine: CATC7
Rated Cap: 36,300 GVW
I had my 6th gear unlocked by a Detroit Diesel Allison Dealer.
All they did was call Allison for the correct S/W and download it to the Bus. The TCM needs to be "married" to the vehicle, and Allison is very strict about what engine gets to twist their gears.
Sixth gear is a good cruising gear, but it can't pull a hill.
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Old 09-13-2021, 11:36 AM   #3
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Join Date: Dec 2017
Location: Dawsonville, Ga.
Posts: 10,321
Year: 1999
Coachwork: Genesis
Chassis: International
Engine: DT466/3060
Rated Cap: 77
Seems anything 2000 or newer Allison will give consent, they wouldn't on my 99.
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Old 09-13-2021, 12:55 PM   #4
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Join Date: May 2006
Location: mid Mo.
Posts: 491
Year: 1976
Coachwork: bluebird
Chassis: F33695
Engine: 427 chevy converted to 466
Rated Cap: 84
Ya sixth won't climb descent hills but it's wonderful on flats, that's what 5th is for.
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Old 09-13-2021, 01:14 PM   #5
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Join Date: Jun 2015
Location: Wisconsin
Posts: 1,236
Year: 2001
Coachwork: Bluebird
Chassis: All American
Engine: 8.3 Cummins ISC
Rated Cap: 75
My bus came with 6th already unlocked

Which is nice because Blue Bird almost never writes 6th gear unlock authorizations.
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Old 09-13-2021, 01:23 PM   #6
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Join Date: Dec 2017
Location: Dawsonville, Ga.
Posts: 10,321
Year: 1999
Coachwork: Genesis
Chassis: International
Engine: DT466/3060
Rated Cap: 77
My bus cruises easily at 80-85mph. Unfortunately it only gets 7+mpg at that speed, I want 6th open just for fuel economy.
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