Allison Transmissions Bus Model

Automatic Models MT 643 up to 210 nhp (157 kW) Transit Bus/Shuttle Bus

Net input power (max).............................210 hp (157 kW)
Input speed range................................2000 - 4000 rpm
Net input torque (max)........................590 lb ft (800 N·m)
Vehicle weight.......................Up to 37,480 lbs (17,001 kg)    

Direct..............SAE 2 flywheel housing with flex plate drive    

Type..........................Single-stage, 3-element multiphase
Stall torque ratio.........TC 350-3.04; TC 360-2.86; TC 370-2.40;
                                        TC 378-2.27; TC 380-1.82
Lockup Clutch, automatic..................Effective in 3rd & 4th    

Type..........................Constant mesh, spur type planetary

         Range                                  Ratios*:
         First...................................3.58:1
         Second..................................2.09:1
         Third...................................1.39:1
         Fourth..................................1.00:1
         Reverse.................................5.67:1
           * Gear ratio does not include torque converter ratio.    

Converter driven (SAE 6-bolt)
Location............................Right side (viewed from rear)
Drive gear ratio................All ranges--1.00 x turbine speed
Drive gear rating.............................300 lb ft (407 N·m)    

Oil type.........................................Dexron II®, C 4
Capacity (excluding external circuits)....18 U.S. qts (17 liters)
                                              (with std. oil pan)
Filter............Full flow, replaceable element, remote mounted
Cooler............................................Remote mounted
(Filter and cooler not furnished on transmission assembly but are supplied
 by vehicle manufacturer.)    

Length..........................................30.4 in (773 mm)
Width...........................................19.3 in (489 mm)
Height..........................(with 5.1" pan) 22.4 in (568 mm)
Weight (dry)....................................510 lbs (231 kg)
+ Vocational ratings may vary by vocation.     

	Designed for use with large bore gasoline and mid-range diesel engines up to 205 nhp (156 kW). Four forward ranges and one reverse. This transmission model is suited for transit and shuttle bus applications.
	Clutches are multidisc design, oil-cooled, hydraulically-operated, and self-compensating for normal wear. Spur-type planetary gears are designed for strength, quietness, and long life.
	Automatic lockup clutch, throttle-modulated for maximized fuel economy and enhanced engine braking. Automatic upshifting and downshifting within each drive range. Built-in inhibitors prevent downshifts or shifts into reverse unless vehicle speed is within an acceptable range.
	The Allison three-element torque converter provides smooth, shock-free operation. A choice of converters permits matching the MT 643 to a wide variety of engines.
	Converter-driven power takeoff drive on right side of transmission (as viewed from rear) is standard. Design is SAE 6-bolt.
	Provisions for neutral start switch, reverse signal switch, SAE regular-duty thread-type speedometer drive, and parking brake.
	5.1 inch oil pan is standard. Optional 4.3 and 7.1 inch pans are available when ground clearance or heavy duty operation dictates their use.

	Fare collection
	Defined route of operation
	Heavy start/stop operation
	Returns to same location at the end of the day
	Facilities for standing passengers
	No luggage facilities

	Regular service between cities
	Special events tours/charter
	No standing passengers
	Luggage provisions
	Premium motorhome chassis

	Airport/hotel/resort transportation
	May be "on call" demand or schedule
	Specialty such as trolley/paratransit/handicap
	Facilities for standing passengers