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Allison Transmission Service - General Questions

Q: What maintenance procedure should on-/off-highway truck operators follow to ensure a transmision does not fail prematurely? Is it a combination of operating techniques and simple maintenance procedure or other criteria?

Q:How do electronics assist maintenance technicians? How do the electronics fault finding capabilities work?

Q:What are the dangers of an untrained individual twisting or 'tweaking' a transmission? Can a 'little knowledge' cause irreparable damage to a system?

Q:What are the most common misconceptions transmission maintenance?

Q: What are the primary causes of transmission failure for trucks used in the construction/demolition sector? How could failures be avoided?

Q: What components in a transmission system are the most sensitive to contamination?

Q: What fluid do I use in my Allison transmission?

Q: What is my oil filter part number?

Q: What model transmission is in my vehicle?

Q: Where do I take my Allison transmission for service?

Q: What maintenance procedures should on-/off-highway truck operators follow to ensure a transmission does not fail prematurely? Is it a combination of operating techniques and simple maintenance procedures, or other criteria?

A: Optimum performance and reliability of heavy-duty automatic transmissions can be noticeably influenced by the type of fluid used and the frequency with which that fluid is changed. Allison Transmission Division and General Motors have designed extensive programs including specifications and tests to verify the quality of fluids and consequently have specific fluid and filter change recommendations. These fluid and internal filter change interval recommendations are listed in the respective transmission series operator's manuals. Additionally, because the transmission fluid cools, lubricates, and transmits hydraulic power, it is important that the proper fluid level be maintained at all times. If the fluid level is too low, the converter, bushings, bearings, and clutches do not receive an adequate supply of fluid. If the fluid is too high, the fluid can aerate. Aerated fluid can cause the transmission to shift erratically or overheat. Additional information regarding fluid/filter change recommendations and maintaining proper fluid level are contained in the MD/HD/B Series Allison On-Highway Transmissions (WTEC III Controls) Operator's Manual - OM2995EN. Transmission operator's manuals are available for viewing and download on the worldwide web at Allison Transmission's web site www.allisontransmission.com by clicking on "Products" then "Publications" and entering the appropriate manual's identification number.

Q: How do electronics assist maintenance technicians? How do the electronic fault finding capabilities work?

A: The World Transmission electronic control system is programmed to inform the operator of a problem with the transmission system and automatically take action to protect the operator, vehicle, and transmission. When the Electronic Control Unit (ECU) detects a problem condition, the ECU restricts shifting, turns on the CHECK TRANS light on the instrument panel, and registers a diagnostic code.

Diagnostic codes are numerical indications relating to a malfunction in transmission operation. Each code consists of a two-digit main code and a two-digit subcode. These codes are logged in a list in the ECU memory with the most severe or otherwise most recent code listed first. A maximum of five codes (numbered d1-d5) may be listed in memory at one time. Diagnostic codes are accessed through the pushbutton and lever shift selectors or the diagnostic data reader. The procedure to retrieve diagnostic codes is listed in the transmission operator's manual. A maintenance technician will use these codes to determine the source of any potential malfunction and to formulate a suitable repair plan.

Q: What are the dangers of an untrained individual twisting or 'tweaking' a transmission? Can a 'little knowledge' cause irreparable damage to a system?

A: As in any industrial or commercial setting it is always unwise to allow untrained individuals to perform any kind of work on complicated equipment. In the case of transmission repairs, improper work practices could result in costly rework efforts, excessive vehicle downtime, and diminished customer satisfaction. For example, over-torquing filter cover bolts may result in stripped bolt hole threads, which would require a transmission removal for main case replacement. Improper testing of an electronic control unit may result in damage to the internal circuits requiring its replacement.

Fortunately for the fleet owner or end-user, Allison Transmission has a worldwide network of authorized distributors and dealers trained and equipped to perform a full range of maintenance and repair procedures. Fleet maintenance personnel may also attend training at an authorized distributor or at Allison Transmission's main manufacturing facility training center.

Q: What are the most common misconceptions surrounding transmission maintenance?

A: The Allison Transmission maintenance schedules stipulate that fluid/filters should be changed after the recommended mileage, months, or hours have elapsed, whichever occurs first. Local conditions, severity of operation or duty cycle may require more or less frequent fluid change intervals that differ from the published recommended fluid change intervals of Allison Transmission. Transmission protection and fluid change intervals can be optimized by the use of fluid analysis.

Q: What are the primary causes of transmission failure for trucks used in the construction/demolition sector? How could failures be avoided?

A: The single most sinificant method for ensuring years of trouble-free service is to perform the recommended transmission fluid and filter maintenance. Some fleet owners have successfully implemented oil analysis programs to monitor and control fluid change intervals as well as provide a means of early detection of pending problems. Additionally, periodic inspections of those truck systems that might directly influence transmission operation such as the vehicle's drive shaft components, electrical charging system, and the transmission oil cooler/vehicle cooling system, etc. should be performed to ensure that deficiencies in these systems do not lead to a transmission malfunction.

Q: What components in a transmission system are the most sensitive to contamination?

A: Solid particulate contamination may have a detrimental effect on the durability of bushings and roller bearing elements inside the transmission. Additionally, fine particulates may degrade the functionality of components in the control module by causing solenoid valves to fail or clutch apply valves to stick.

The presence of water and/or ethylene glycol coolant mixtures in the transmission oil is detrimental to the reliabilty and durability of the internal components. This foreign liquid has a deteriorating effect on non-metallic components (rubber, gasket material, etc.) and on highly loaded steel parts, such as bearings and gears, due to reduced lubricity. Frictional capacity of drive clutch plates can be greatly reduced, as a result of surface film or impregnation and the presence of glycol will physically deteriorate clutch plate material.

Q: What fluid do I use in my Allison transmission?

A: Follow this link to Transmission Fluid Recommendations. This document includes information about Allison oil recommendations, oil specifications and Allison/Castrol TranSynd™. Other topics discussed are:

* Fluid recommendations for each transmission model
* Cold weather vs. fluid viscosity
* Used oil analysis for improved fluid performance

Q: What is my oil filter part number?

A: You should reference the Parts Catalog for your transmission model. If you do not have a Parts Catalog you can call the Allison Facility near you.

Q: What model transmission is in my vehicle?

A: Check your vehicle/order paperwork. If you cannot find the model designation, call an Allison Distributor or Dealer for assistance. Before calling Allison please have the following information ready:

* Type of vehicle - Refuse, dump truck, etc.
* HP of your engine
* Description of your shift selector
* Age of your vehicle
* Serial number of the transmission - if possible (check nameplate on the side of the transmission).

Q: Where do I take my Allison transmission for service?

A: Take your vehicle to an authorized Allison Distributor or Dealer. These Allison Facilities may offer full service or provide only simple maintenance on easily accessible components.



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