How to spot potential transmission problems when test driving a used car
Automatic transmission cut in half.
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It's not a secret that the transmission is one of the most expensive components in a vehicle to repair. Is it possible to thoroughly test the transmission during a quick test drive? Of course not, but if you know what to look for you might be able to recognize some of the early signs of potential problems. First, let's see what the common transmission problems are:
Conventional automatic transmission
Mazda Skyactiv automatic transmission
The most common issues are delayed engagement, harsh shifting and slipping.
For example, we tested Honda Odyssey recently that drove well, except when in reverse. When shifted in reverse, after a delay, you'd feel a strong jolt. This was a sure sign that the transmission was going to fail soon.
Delayed engagement is often more noticeable when the vehicle is started cold. You shift into Drive and for a while, nothing happens. Then, in a second or two, you feel the transmission engaging. This is also a sign of wear. A good transmission engages almost immediately as soon as you shift into Drive or Reverse.
Recently, our colleague came across a used BMW X5 that was in excellent shape. However when we test drove it, we noticed that the shift from 5th to 6th gear felt harsh. In other words, there was a pronounced lurch during shifing into 6-th gear. All other shifts were smooth. However, we steered clear of this vehicle, knowing that it will need a new transmission soon.
In some older Mazda 3 cars, the transmission control module may fail. The symptoms include the AT warning light coming on and rough shifting. If an AT warning light comes on during a test drive, avoid the car.
Slipping in gear or between shifts is another common problem. The car may drive fine for a while, but later you may notice slipping. It feels like during a shift, the transmission drops into neutral, then shifts with a delay. You also may notice that the engine revs, RPMs increase, but the vehicle isn't moving any faster, like in neutral.
In some cars, the transmission stays in one gear longer, then shifts at higher than usual RPMs. This is called delayed shifting and is also a sign of a transmission problem. In most cars, under normal gradual acceleration the transmission should shift somewhere between 1800 and 2300 RPMs. It may shift at higher RPMs under hard acceleration.
Continuously variable transmission
Continuously Variable Transmission
Many newer cars (e.g Nissan, Subaru, Audi) have a continuously variable transmission (CVT) where the gear ratio is changed by varying the sizes of pulleys connected by a metal belt. Some of the CVT problems include a loud whining noise, slipping, rattling, shudder on acceleration, jerky transmission engagement and leaks.
For example, we test drove a Nissan Sentra with a CVT transmission. It drove fine, but during coasting it would make a metal rattling noise that would go away when accelerated. A Nissan Murano with a CVT transmission we came across a while back, would drive fine for a while but then would start to shudder on acceleration. If a vehicle exhibits any of these symptoms, it should be avoided. Also, if you are planning to use your vehicle for towing, the CVT transmission is not a best choice for that.
Common problems with a manual transmission include a slipping clutch, grinding when shifting into gear, whining noise, vibration in the clutch pedal and the shifter popping out of a gear.
The clutch issues are more common, especially at higher mileage.
A worn out clutch feels like slipping on acceleration and may also produce a very distinct burnt smell coming from the engine compartment. One of the early signs of a worn out clutch is when the clutch starts engaging at the very top of the pedal travel.
A bad release bearing may produce a metal screeching noise when the clutch pedal is depressed. The noise goes away when the pedal is released. In some cars, worn-out synchronizers may cause the transmission to grind when shifting into a gear. Another common issue is when the shifter pops out of gear by itself while driving.
A good manual transmission should shift into any forward gear without grinding and should not make any loud noises. Normally, the clutch should start engaging somewhere in the middle of the clutch pedal travel when it's released. The clutch should release and engage smooth without shudder or noises.