School Bus Fleet
MenuMENU
SearchSEARCH

3 keys to maintaining automatic transmissions

Premature failure of your automatic transmissions can be minimized through proper spec'ing, preventive maintenance and technician training. By includi...

by David M. Sluder
February 1, 1998
3 min to read


Premature failure of your automatic transmissions can be minimized through proper spec'ing, preventive maintenance and technician training. By including these items in your maintenance program, it will help to ensure that you realize the maximum potential of the transmission. First step is right spec
For any piece of equipment to perform as it was designed, planning is required. The automatic transmission is no exception to this rule. The first step to prevent premature failure is to ensure that the right transmission is included in the purchase specifications. I will further clarify this statement with the following statement: Cheapest is not always best. By including in your specs a transmission that is not continually taxed to its limit, you can avoid premature failure. This will result in reduced cost over the life of the vehicle. Pay attention to intervals
The transmission oil level should be checked at the intervals specified in the vehicle operator's manual. Most transmission manufacturers recommend that the oil and oil filter be changed every 25,000 miles or 12 months, whichever occurs first. The transmission governor filter should be changed at the same time. Most auxiliary filters should be changed after the first 5,000 miles and thereafter at normal oil change intervals. Transmission oil may require change sooner than recommended depending on operating conditions. Oil must be changed whenever there is evidence of dirt or a high temperature condition indicated by discoloration, strong odor or oil analysis. Local conditions, severity of operation or duty cycle may dictate more or less frequent service intervals. At each oil change, examine the oil that is drained for evidence of dirt or water. A normal amount of condensation will emulsify in the oil during operation. However, if there is evidence of water, check the cooler (heat exchanger) for leakage between the water and oil areas. Oil in the water side of the cooler is another sign of leakage. If engine coolant leaks into the transmission oil system, immediate action must be taken to prevent malfunction and serious damage. The transmission must be completely disassembled, inspected and cleaned. All traces of the coolant and varnish deposits resulting from coolant contamination must be removed. Inspect the fluids closely
Metal particles in the oil or on the magnetic drain plug (except for the minute particles normally trapped in the oil filter) indicate transmission damage. When these particles are found in the sump, the transmission must be disassembled and closely inspected to find the source. Metal contamination will require complete disassembly of the transmission and cleaning of all internal and external circuits, cooler and all other areas where the particles could lodge. The transmission breather is located at the top of the transmission housing and serves to prevent pressure buildup within the transmission. The breather must be kept clean and the passage open. The presence of dust and dirt will determine the frequency at which the breather requires cleaning. Training is worthy investment
One area that is often overlooked in the industry is providing adequate training for technicians, who must stay abreast of new transmission technology. Most automatic transmission suppliers offer excellent training, and some will even provide on-site instruction. Training your technicians is certainly money well spent. It will teach your employees to properly diagnose a problem instead of guessing or changing parts until the problem is fixed. David M. Sluder is a transportation consultant for the North Carolina Department of Public Instruction.

Subscribe to Our Newsletter

More Maintenance

Portrait of John Gonzales of the National Laboratory of the Rockies featured in School Bus Fleet’s “Five Questions” Q&A series.
Maintenance•by Amanda Huggett•November 1, 2026

Easy Ways to Reduce School Bus Emissions: Q&A with John Gonzales

Learn how preventive maintenance, driver training, reduced idling, smarter routing, and the right fuel choices can help districts reduce emissions — without investing in new buses.

Read More →
Automotive technician handling a large tire and wheel assembly beside a Ranger DST30PX wheel balancer and tire-changing equipment in a professional repair shop.
Maintenance•October 16, 2026

BendPak Launches Ranger DST30PX Wheel Balancer

BendPak's new wheel balancer handles tires up to 43 inches in diameter, with a reinforced design, precise weight placement, and faster service cycles.

Read More →
School bus maintenance garage with several yellow buses undergoing service, mechanics working in repair bays, and overhead equipment. Graphic reads “A Better Garage, All Year Long” with the School Bus Fleet logo.
Maintenance•October 14, 2026

Tips for Ensuring School Bus Garages Are Safe and Warm Year-Round

Cold maintenance bays and rising heating costs? Learn how school bus garages can improve comfort with targeted heating, better airflow, and winter preparation.

Read More →
Ad Loading...
Graphic featuring a close-up of a yellow school bus with the headline “ASE's 7 School Bus Technician Certification Tests: What to Know.”
Maintenance•by Staff and News Reports•October 8, 2026

ASE Highlights School Bus Technician Certification Requirements

ASE is encouraging school bus maintenance professionals to maintain their certifications, highlighting seven specialized tests and five-year renewal requirements.

Read More →
Fleetrite logo displayed against a light background with a blurred close-up of a vehicle in the upper right corner.
Maintenance•by News/Media Release•October 1, 2026

International Adds E-Commerce Capabilities to Fleetrite.com

IC Bus customers can now browse, buy, and track shipments for more than 400,000 aftermarket parts online.

Read More →
Graphic featuring several yellow school buses with the headline, “The Most Expensive School Bus Resale Mistake,” and images representing maintenance, auctions, and resale value.
Management•by Steve Mitchell•October 1, 2026

The Most Expensive Thing You Do Before Selling a School Bus: Wait

When should you sell an aging school bus? Learn how maintenance, mileage, corrosion, specifications, and timing can affect resale value long before the auction.

Read More →
Ad Loading...
Graphic showing a DEF header beside the text, “Better DEF Header Technology Can Mean Fewer Repairs.”
Maintenance•September 18, 2026

The Evolution of DEF Header Technology: What School Bus Operations Should Know at Replacement Time

See what school bus fleets should consider when replacing DEF headers to improve reliability, reduce repeat repairs, and control maintenance costs.

Read More →
The Essential Guide to School Bus Fleet Maintenance
Sponsored•September 8, 2026

The Essential Guide to School Bus Maintenance and Student Safety

Your district's buses carry students to school every day. This guide shows how predictive maintenance powered by fleet data helps keep buses reliable, drivers accountable and students safer from the first bell to the last stop.

Read More →
School buses at a Southeast Michigan facility illustrate Kerry Brothers’ growing regional maintenance network following its acquisition of Downriver Truck and Bus.
Maintenance•by Amanda Huggett•August 11, 2026

Kerry Brothers Grows Michigan School Bus Repair Network

The acquisition of Downriver Truck and Bus expands Kerry Brothers’ school bus maintenance footprint across southeast Michigan, adding repair capacity, diagnostic resources, and state inspection support.

Read More →
Ad Loading...
A black and green Noregon CAN Mentor graphic.
Maintenance•by Staff and News Reports•July 24, 2026

Noregon Introduces CAN Bus Diagnostic Tool, Expands JPRO Features

CAN Mentor and the latest JPRO update aim to simplify vehicle network diagnostics and improve repair efficiency for technicians of all experience levels.

Read More →