Once upon a time cars were simple: If the transmission didn’t shift right, you probably had a transmission problem. You took your car to the transmission shop and they fixed it. Simple, right?

As with most stories that begin this way, times have changed. Today, when your car’s transmission isn’t shifting right, well, it could be the transmission, but there’s just as good a chance that it’s something else… something seemingly unrelated to the transmission.

For example, You’re driving down the highway. The converter clutch locks up, right on time. Then, suddenly, the car begins to lurch and buck. Bad converter clutch, right?

Maybe. Maybe not. It could also be a problem in the converter clutch solenoid or the solenoid control circuit, opening and closing erratically. Then again, you could have a bad spark plug.

Wait, a bad spark plug? How would that cause the car to buck when the converter clutch comes on?

Actually, the situation is more common than you’d think. When the computer applies the converter clutch, it also leans out the air/fuel mixture, because it thinks you’re approaching cruise levels. And, with the transmission locked to the engine, the converter clutch increases the load on the engine, while eliminating any cushion between the two.

So, if a spark plug is worn, the extra load, combined with the leaner mixture can degrade the spark, causing an intermittent misfire. And since there’s no cushion between the engine and transmission, you feel every misfire through the entire car. Replacing the spark plugs eliminates the misfire, and improves the car’s performance.

This is just one example of how a seemingly unrelated condition can appear to be a transmission problem.

How can you identify the actual cause of the problem? You can’t. Not yourself, anyway. This is where an experienced technician comes in. The technician knows where to look for problems of this nature, and is equipped to isolate and pinpoint the root cause of those problems.

It’s also why you need to expect to pay for diagnosing those problems. Because very often, finding the source of that buck or slip is the most demanding part of the job. And in the case of the faulty spark plug, the diagnosis is what takes the most time. It just doesn’t make sense to expect the technician to supply his knowledge and experience without getting paid.

It’s also another reason why it’s so important to let our shop know exactly what you’re experiencing, without trying to diagnose the problem yourself. If you brought that car into the shop and asked for a transmission repair, you might have found yourself paying for work you didn’t really need. Because if the technician doesn’t know there’s a problem, he won’t be able to diagnose it for you.

As your local ATRA Member shop, O’Neill Auto & Transmission Service is equipped with all of the tools, training, and technical support necessary to identify the root cause of your car’s problems, and will be happy to help identify and correct those problems as quickly and inexpensively as possible. You just want to meet us halfway, by explaining the condition instead of trying to diagnose it yourself.

From the AUTOMATIC TRANSMISSION REBUILDERS ASSOCIATION