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Allison Transmissions

 

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

SPECIFICATIONS

Cross-Section | Features & Benefits | Typical Applications | SCAAN Specification Assistance

General rating+

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)    

Mounting

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

Torque converter

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    

Gearing

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.    

Power takeoff provision

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 system

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.)    

Size

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.     

 

Transmission Cross-section (go to top)

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Design Features & Benefits (go to top)

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.

 

Typical Applications (go to top)

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.

SCAAN Specification Assistance (go to top)

To be sure that you get the most efficient engine/transmission package for your operation in your territory with your preferred vehicle, your local Allison Transmission distributor offers SCAAN.

SCAAN stands for System for Computerized Application ANalysis and helps take the guesswork out of vehicle-buying decisions. What's more, it does so quickly and accurately through computer terminals located at all distributor outlets. This means rapid analysis of your vehicle needs on the spot.

SCAAN can compute a wide variety of vehicle performance parameters, including gradeability, acceleration and retardation. SCAAN will also check your powertrain specifications against Allison Transmission vocational experience to insure satisfactory vehicle performance.

SCAAN is user friendly. Interactive operation allows alternate vehicle configurations to be quickly evaluated to insure optimized powertrain selection.

 

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Headquarters Phone: 1.800.999.8726(TRAN)
2339 E. Grauwyler Rd. Fax: 972.579.7466
Irving, TX 75061 Email: WeAreAllison

 

 

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