Transmissions: Repair or Replace?

Deciding whether it is best to repair or replace a transmission when complications occur is no easy matter. The answer is wide-ranging, and one that requires careful consideration of many key factors before deciding upon the best option.

To learn about what is involved in this decision-making process, Fleet Maintenance editor David A. Kolman turned to Eaton Corporation - a major supplier of medium and heavy duty transmissions to the North American trucking industry, and to Allison Transmissions - the world’s largest manufacturer of fully-automatic transmissions for medium and heavy duty commercial vehicles, medium and heavy tactical U.S. military vehicles and hybrid-propulsion systems for transit buses.


The following information was provided by Matt E. Colwell, global product strategy manager - vehicle group, for Eaton Corporation.

A good point to begin is defining the differences between repairing and replacing.

- Repairing - This is an attempt to fix the item or component that has failed in the transmission, but may not necessarily fix the root cause of the failure. Depending upon the depth of the repair, this may be the least expensive option. 

However, repairing can be more time-consuming than replacing, thereby requiring a vehicle to be off the road not generating income.

When opting for repairing, it is very important to note that the repair will only be as good as the service provider doing the repair. Eaton strongly recommends that the provider has the necessary training and experience and uses only genuine OEM-approved components to ensure the repair is done correctly and to help prevent the problem from reoccurring.

- Replacing - This is essentially the purchase and installation of a new, used or remanufactured transmission. New transmissions, of course, provide best-in-class benefits in the areas of reliability and performance, and at Eaton come with up to a three-year warranty. 

Used transmissions present a value-priced option for customers who want to quickly get back on the road, the length of which is determined by the quality of the used transmission purchased.

- Remanufacturing - This is a more thorough process of bringing a used product, or core, back to its intended functionality. Be careful here however, as all remanufactured transmissions are not the same. 

Too many re-builders are conducting business these days with pseudo-remanufactured offerings that do not deliver a highly reliable product. These rebuilders repair what they think is the problem, but do not ensure each component is 100-percent ready for the application. 

An example of this often occurs with the shift yoke pad thickness on Eaton’s Fuller Reman heavy duty transmissions. Many rebuilders only visually inspect the yoke pad thickness for reuse. This can lead to improper shift engagement on the sliding clutch causing shift problems.

Conversely, and like those made by Eaton and other quality transmission suppliers, value-added remanufactured products include 100-percent genuine replacement parts, complete inspection of every component used, use of the proper lubricants and functional dyno testing to ensure the finished unit adheres to all OEM specifications.

Warranty coverage on remanufactured transmissions is also an important consideration. If a rebuilder is unwilling to back up the reliability of its transmission product with a solid warranty, can you really trust it on the road?  

Other areas that should be addressed to help determine the best option include vehicle application, desired service life, failure type, total lifecycle cost and noise vibration and harshness (NVH).


In some applications, perhaps with a multiple truck fleet that can have one vehicle down for lengthy repairs, the option of repairing a transmission makes good, practical sense. While a subsequent repair should be expected and may be a nuisance, the disruption could have little impact on profits.

Downtime will, in most cases, impact the profits of an owner operator or fleet engaged in over-the-road hauling. In these applications, a quality “reman” product will typically be the better choice rather than days or weeks of downtime. 

Having confidence that the unit will be reliable for the long term is another reman advantage.


For those individuals or fleets planning to operate their vehicles for one or two years, they may not want to invest in replacing the transmission and opt for a repair. That decision may be a sound one.

On the other hand, with more and more fleets extending buying cycles and looking at vehicle service lives of four to five years or more, they may want to consider a reman or other replacement product and the reliability, performance, service and warranty features that are included with the product. 


While all failures are bad, some are not as bad as others, and the possible scenarios are countless. That noted, here is a look at a few examples that can influence the repair versus replace decision.

Definitely consider a replacement transmission when a failure occurs in the main case assembly. For example, replace the transmission in a situation where an overdrive gear cracks and runs through the transmission, damaging multiple gear sets. 

Also, consider replacement if a cooler blowout occurs, possibly cooking the inside of the transmission. 

In both scenarios, the repair can be very time-consuming and there is no guarantee the root cause of the failure will be fixed.

But, you may want to consider repairing for issues along the lines of harsh shifting that may be related to the air system on the transmission. A leak in the system may be occurring, requiring nothing more than replacing the rear seal. 

Another minor repair may be related to slow or incomplete shifts caused by oil ingestion in the back box. The remedy may be as simple as replacing the range bar. 

It doesn’t make good sense to pursue a replacement with these and other minor repairs.

With failure types, it is also important to note that certain transmission problems may not have anything to do with the actual transmission. Excessive driveline vibration, for example, can cause synchronizer pins to break.

You can repair the problem all day long, but the failures will continue to occur until you fix the vibration problem. Swinging into a reman product, of course, will be just as futile. Fixing the vibration will fix the transmission.


Often when repairing a failed transmission, the root cause of the problem is not properly addressed. Damage to additional internal components often results from the initial failure leading to additional repair bills down the road. 

Those costs can add up quickly. When that becomes more of the norm than the exception, it may be a good time to consider a replacement transmission.

In the case of Eaton’s Fuller Reman transmissions, keep in mind that each transmission has been 100 percent inspected. Crack and leak inspection, bore diameter gauging, bearing replacement and dyno testing are just a few of the precautions Eaton takes to ensure best-in-class reliability. And with the exclusive use of genuine components, a more robust and reliable product is built to generate consistently lower lifecycle costs.


Warning signals during the day-to-day operation of a transmission may also help determine the merits of replacement versus repairing. 

For example, a slow shift when shifting between gears may require a simple repair, much like the case with the back box range bar noted earlier. But if there is a lot of vibration and excessive noise coming from the transmission, then a replacement may be the best option.

The vehicle operator plays an integral role in determining just how severe noise, vibration or harshness is in the transmission. 

In any event, that information should always be given to a qualified and trained technician or service center so they can determine the cause of the problem and then determine whether it is best to replace or repair.


While the pros and cons of replacing versus repairing are many, the best advice we at Eaton can give is to always deal with an experienced and properly trained service provider. Also, be sure that provider always uses genuine, OEM-approved components.

Doing so, the level of certainty in the uncertain world of replace versus repair is sure to deliver better reliability, performance and lower total lifecycle costs.


Dennis Breedlove, director, global channel development and aftermarket programs for Allison Transmission, provided the following information.

- Repairing - Qualified repair facilities can correct nearly any transmission problem.  These types of repairs are done on a “time and material” basis. 

In these cases, the technicians diagnose the problem, disassemble the transmission to the extent necessary and then reassemble the unit with needed new parts. As a final step, the unit is dyno and/or road tested. 

- Replacing with a remanufactured transmission - Replacing a failed unit with a remanufactured one - also referred to as rebuilt, overhauled or reconditioned - offers customers the advantages of typically faster repairs, as well as the assurance of a quality repair. In this process, it is obviously important to use quality remanufactured products. 

Unfortunately, there are many rebuilders that use improperly trained technicians and inferior quality new parts or excessively worn used parts. Such shortcuts typically render a competitively priced transmission, but the unit reliability most often suffers. 

In the world of remanufactured transmissions, the old saying of “you get what you pay for” usually applies.

- Replacing with a new or used transmission - Usually, failed transmissions are replaced with new transmissions only if the vehicle itself is of recent vintage. 

As with most modern commercial transportation products, transmissions rely on electronic controls for an ever-increasing level of performance. As these products are commonly updated with more and more capable controllers, it is important to match the proper transmission vintage to the vehicle being repaired. 

For example, it would usually not make financial sense, nor may it even be possible, to service a 10-year-old vehicle with a new vintage transmission. There would likely be compatibility issues with the integration of the new transmission electronics and those of the old vehicle.


If the transmission problem is relatively minor, repairing the unit is usually the most cost-effective and quickest method to get the vehicle back into revenue service. However, if the extent of a failure is significant, the time necessary to make repairs will obviously increase correspondingly. 

At some point replacing a failed unit with a new or remanufactured transmission can often be the fastest and most cost-effective method.

Another consideration when major repairs are needed is with regard to warranties. Often, companies provide a longer and more comprehensive warranty for completely remanufactured transmissions relative to a simple time and material repairs. Of course the extent and cost of the necessary transmission repair is a major factor in this decision process.

Total cost is usually the key factor when deciding on repair options. Total costs include not only the expense of the actual repair, but the cost of lost revenue opportunity when the vehicle is out of service. 

Particularly since the economic recession began, customers have become increasingly interested in minimizing fleet downtime. The costs associated with vehicle removal from revenue generating service becomes one of the areas of greatest concern. 

Failures that in the past may have been repaired by a transmission shop are often replaced with a remanufactured or new unit as the preferred method to get the vehicle on the road as quickly as possible.

Additionally, the age of a vehicle is usually considered when deciding on repair options.  Owners of late model vehicles typically will give greater consideration to quality remanufactured or new replacement units as they have interest in long-term reliability and durability. 

On the other hand, owners of late-in-life vehicles often seek an option that will enable the vehicle to return to operation at the lowest price point. Long-term durability of these type repairs is of secondary concern.


Today’s commercial transmission are very sophisticated products. For this reason, proper training of technicians is more important than ever. In the case of the Allison authorized service network, factory-approved training is required of all technicians that perform transmission repairs. 

Attempts to repair transmissions by under-trained or untrained techicians can lead to excessive downtime, misdiagnosis or can even cause additional problems or catastrophic and expensive failures. 

Beyond being a necessity for making accurate repairs, proper training is also required in order to take advantage of key diagnostic capability of Allison products.

Allison authorized service locations offer Trans Health service for recent vintage transmissions. Trans Health is a diagnostic process wherein the computer can be utilized to check and measure key wear components of the transmission without requiring any level of transmission disassembly. The computer can warn of impending clutch failures and thereby enable customers to schedule repairs on a more convenient basis. 

What’s more, replacing worn components before an actual failure occurs greatly reduces the total expense to the customer. Such a pre-emptive repair enables the worn part to be inspected and replaced as necessary, before it fails and causes a chain reaction of neighboring part failures.


In the repair process, an accurate diagnosis is most critical in making proper fixes, as well as minimizing downtime. For dealing in the complex world of electronic controls, Allison has created diagnostic tools to assist in determining the root cause of problems. 

The need for proper tooling and corresponding training is evident when considering situations wherein inadequately equipped or trained technicians misread the symptom and thereby waste time and add expense by pursuing false corrections. 

For example, symptoms may manifest as improper transmission shifting, when in reality the problem is not an internal transmission issue at all but rather a problem caused by faulty vehicle wiring, a cooling system issue or possibly another powertrain component control system malfunction. Very often, only knowledgeable and properly equipped technicians can pinpoint and correct the true cause of problems, and do so in a timely fashion. 

Equally important for making quality repairs is the need to use quality parts. At authorized Allison service locations, only genuine Allison parts are used for repairs. 

In Allison's opinion, non-genuine parts often fail prematurely and in doing so, can cause expensive secondary damage. Any upfront cost savings attained through the use of inferior parts quickly disappears when a failure is compounded or a repeat failure occurs. 

From simple repairs to complete transmission replacement, the vital elements in quality service are the same today as they have always been, but likely to a higher degree than ever before. Quality repairs are the result of proper training, proper tooling and quality replacement parts. 

The combination of these service elements will insure long-lasting and cost effective repairs.



Bendix increases focus on remanufacturing

Bendix Commercial Vehicle Systems has launched a new business unit to focus on and expand its remanufacturing output.

Each Bendix business unit had been responsible for both its original equipment and aftermarket products. Now, the new business unit consolidates all remanufacturing efforts as part of the company’s aftermarket business.

Bendix develops and supplies leading-edge active safety technologies, air brake charging and control systems and components under the Bendix brand name for medium and heavy duty trucks, tractors, trailers, buses and other commercial vehicles throughout North America.

Steve Mance, Bendix vice president and general manager of the Charging group, says reasons for establishing the new unit include offering buyers lower-priced alternatives to new parts and ensuring long-term and peak-demand product availability.

“We can remanufacture products that went out of OE production as many as 30 or 40 years ago,” he says. “And in peak OE years, we can ensure product availability when other manufacturers are out of capacity because we’re producing remanufactured parts.”

While the lower cost of a remanufactured part compared with a new part often appeals to end users, Mance points out that remanufactured parts also have a warranty advantage over used parts.

“We follow the same robust release process as an OE product, so we’re testing and remanufacturing to the most current OE specifications,” he explains. “Because of that, we are able to guarantee the remanufactured part for the same period of time as the OE product warranty.”


Growth in the remanufacturing industry reflects its appeal. Mance notes that remanufacturing for Class 6, 7 and 8 trucks and trailers in North America was a $3.1 billion market in 2010, and that is expected to grow to $4 billion by 2015.

The Bendix remanufacturing unit also enables the company to bring to market remanufactured components originally manufactured by other brands. Since not all product cores make their way back to their original manufacturer, Bendix engineers can now use parts from those product cores to bring remanufactured parts as close as possible to their OE specifications.

He says Bendix plans to build its remanufacturing business not only by branching out into products beyond braking systems, such as powertrain components, but by sharing its remanufacturing strategy with its parent company, Knorr-Bremse, a worldwide producer of pneumatic, hydraulic and electronic braking systems and chassis management systems for commercial vehicles.