Technical Paper

Transmissions: Repair or Replace

by Matt E. ColwellGlobal Product Strategy Manager – Vehicle Group, Eaton Corporation

September , 2011

As a major supplier of medium- and heavy-duty transmissions to the North American trucking industry, Eaton has a wide range of customers who often ask if it is best to repair or replace a transmission when complications occur. The answer is wide-ranging, and one that requires maintenance supervisors to carefully consider many key factors before deciding on the best option.

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

Repairing a transmission 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 with the use of only genuine OEM- approved components to ensure the repair is done correctly and to help prevent the problem from reoccurring.

So if you want peace of mind, get yourself a good mechanic.

Replacing is essentially the purchase and installation of a new, used or remanufactured transmission. New transmis-sions, 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 trans-missions present a value-priced option for customers who want to quickly get back on the road, the length of which is deter-mined by the quality of the used transmission purchased.

Remanufacturing is a more thorough process of bringing a used product, or core, back to its intended functionality. Be careful here however, as all remanufac-tured 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 trans-mission 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 remanufac-tured transmissions is also an important consideration. Eaton recently raised the standard warranty coverage of its HD reman transmission portfolio to two years for line haul and 18 months for vocational applications within the U.S. and Canada. If a rebuilder is unwilling to back up the reliability of their 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 life-cycle cost, and noise, vibration and harshness (NVH).

Application

In some applications, perhaps with a fleet with multiple trucks that can have one down for lengthy repairs, the option of repairing 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.

Service Life

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 its reliability, performance, service and warranty features that are included with the product. The Roadranger service network offers value beyond the initial sale and backs all of Eaton’s Fuller Reman transmission products.

Failure Type

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 transmis-sion 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 vibra-tion will fix the transmission.

Life-Cycle Costs

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 life-cycle costs.

NVH (Noise, Vibration, & Harshness)

Warning signals during the day-to-day operation of a trans-mission 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 transmis-sion, 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 deter-mine the cause of the problem and then determine whether it is best to replace or repair.

Yes, the pros and cons of replacing versus repairing are many.

But the best advice we at Eaton can give is always deal with an experienced and properly trained service provider. Also be sure that same technician 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 life cycle costs.

Example of a damaged gear

Example of a broken synchronizer

Eaton CorporationVehicle GroupP.O. Box 4013Kalamazoo, MI 49003 USA800-826-HELP (4357)www.eaton.com/roadranger

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