Allison Transmissions

Automatic Models MT 643 up to 250 nhp (186 kW)

Net input power (max).............................250 hp (186 kW)
Input speed range................................2000 - 4000 rpm
Net input torque (max)........................640 lb ft (868 N�m)
Vehicle weight (GVW or GCW)..........Up to 73,280 lbs (33,239 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� III, C 4
Capacity (excluding external circuit).....18 U.S. qts (17 liters)
                                                 (w/std. oil pan)
Filter............Full flow, replaceable element, remote mounted 
Cooler............................................Remote mounted 

(Filter and Cooler not furnished on transmission assembly but is 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)
Weight (dry) w/output retarder..................638 lbs (289 kg)
+NOTE: Vocational ratings may vary by vocation.     

	Designed for use with large bore gasoline and mid-range diesel engines up to 250 nhp (186 kW). Four forward ranges and one reverse. This transmission model is best suited for school bus, P&D, emergency vehicles and motorhomes.
	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 take-off 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.

	Shorthaul Tractor
	P&D Truck
	Fire Truck
	Utility Truck
	Stake Truck
	Dump Truck
	Flat Bed Truck
	Motorhome
	Beverage Truck
	School Bus
	Refrigerated Van
	Refuse Truck
	Tanker Truck
	Wrecker
	Other applications are available.