Transmissions: Repair or Replace?

The factors to consider before deciding the best option.

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.

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