Transmission shutters? Slips?

Transmission shudder is a recurrent problem that afflicts millions of vehicles nationwide. But while the issue is common, its causes are not always easy to find. Here’s a look at how to troubleshoot this frequent complaint.
What Is Transmission Shudder?
Drivers usually notice transmission shudder when they are driving between 40-60 mph. They feel the vehicle begin to shake, as if they just drove over a rough patch of road. The sensation lasts for 3-4 seconds, then everything returns to normal – for the time being.
The cause may seem clear: transmission issues caused by failing fluid or a slipping torque converter clutch (TCC). But is this necessarily the case? Here’s a step-by-step process for getting to the root of the problem.
• Check trouble codes, as the vehicle’s computer may tell you all you need to know about what’s causing the shudder. It may also reveal other issues with the automobile. In either case, it’s important to fix codes before proceeding further.
• Use your shop scanner to monitor the vehicle when the shudder occurs. Note whether or not the TCC slips at the same time. If so, then you have located the problem. If not, then the issue may not be with the transmission at all, but with the engine. Common engine-related causes of shuddering include: misfiring plugs, a mis-calibrated vehicle computer, and bad fuel intake. Monitor the engine during shuddering to detect these issues.
• If the TCC does slip during the shuddering, then it is almost certainly at fault. But, before you begin replacing parts, check online for any technical service bulletins (TSB) released by the manufacturer. This may point you to the real cause when nothing else will. For example, GM recently issued a TSB for it 6T70/75 unit, explaining that shuddering is often caused by poorly connected ignition ground coils. Only after checking for a TSB-related issue should you proceed to additional troubleshooting steps.
• Shuddering is often caused by a loss of transmission fluid pressure. Adjusting the solenoid to increase this pressure may eliminate the shudder. If you suspect that the fluid is at the root of the problem, then flushing the system and adding new oil is the next step most shops take. But, before doing so, drop the pan and look for debris in the fluid. If you see this, or if you have other reasons to suspect worn components, then you will need to replace parts as necessary.
• There are additives that promise to “instantly fix” transmission shudder simply by adding them to the fluid. However, these compounds are, at best, only a temporary fix. Using them is like putting an adhesive bandage on a cut that needs stitches. A professional transmission technician should never rely on these products.
Transmission shudder is a common problem with many possible causes. It’s vital that the technician carefully troubleshoot the issue before attempting to resolve it. Taking the time to ensure that the root issue has been found will pay off in the long-term, both for the customer and for the shop’s reputation.

Categories: Transmission slips

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