Quick Facts About Transmission Problems
- Vehicles that need a new clutch often need many accompanying parts replaced at the same time.
- Automatic transmissions are far more complex than their manual counterparts because they have twice the number of parts and sophisticated electronics.
- Checking transmission fluid is the first step in diagnosing automatic transmission problems.
Transmissions are an incredibly complex part of your vehicle. If you Google “transmission interior parts,” you’ll see an overwhelming number of images of assorted gears, clutches, converters, strange-looking bearings, and shift levers, all of which must work in harmony to get you down the road. The problem is, if they aren’t well maintained, they will fail, leaving you with a big bill to pay, but Kelley Blue Book can help with transmission repair.
Here’s what to look for in various transmission types and the problems you may encounter.
Manual Transmissions
Manual transmissions require a host of ancillary components to facilitate gear changes. While most owners are well aware of the gearbox (it attaches to the stick shift poking out of your console), it is generally the clutch system, which disconnects the engine from the drivetrain to change gears quickly and smoothly) that exhibits the highest number of issues. After selecting the desired gear, the driver can release the clutch, and the vehicle can move faster in this new gear.
Most clutch systems use a single or series of clutch discs. Over time, the clutch disc will wear and could slip. If you push the throttle and the engine rpm increases, but the vehicle speed does not, the clutch needs, at the very least, an adjustment. In many cases, the clutch disc could need replacement. Here are some of the more common issues that point to the clutch system as the culprit.
Manual Transmission Problem Signals
- Chattering or scraping: If your clutch chatters when the clutch pedal is depressed, it could be something as simple as an adjustment. The worst-case scenario is a loss of clutch friction material from the disc’s surface. You’ll also feel an imbalance in the clutch pedal. If the pilot bearing has failed, the chatter could be from excessive play in the input shaft.
- Grinding: This most commonly signals a failure of either the clutch disc or the throw-out bearing. (This bearing depresses the fingers on the pressure plate releasing the clutch to allow for gear changes.) Throw-out bearing replacement requires the removal of the transmission gearbox.
- Rattling or Clunking: When modern dual-mass flywheels, found chiefly in modern cars (such as Corvettes) and trucks start to fail, they do so with lots of fanfare. The noise is traceable directly to the springs within the flywheel. Replacement flywheels can cost between $400 and $1,000 alone. Also, there are plenty of other things that can rattle or clunk in a clutch, most of these noises signal the shedding of clutch disc-facing material.
If the vehicle needs a new clutch (always enlist the help of a professional to make this decision), many accompanying parts should be changed at the same time. Replacement parts include the clutch disc(s), pressure plate (which holds the clutch to the flywheels), a resurfacing of the flywheel and rebalance, a new throw-out bearing, and perhaps a pilot bearing or bushing. Among the other things to inspect when installing a new clutch is the clutch fork (for manual clutch systems) and/or the slave cylinder system on hydraulic clutch units. The cost for a new clutch ranges from $1,000 to $3,000 depending on the vehicle.
Manual Gearbox Woes
The reason we spent so much time on clutch diagnosis is that manual transmissions are less troublesome. As long as you keep oil levels up (see your vehicle owner’s manual), the most common problem plaguing the transmission gearbox is misuse (grinding the gears through lack or improper clutch use) which causes the synchronizing collars to malfunction. Over time, they can become worn and burred chiefly due to either clutch misadjustment or poor shifting technique. Made most commonly from brass or bronze, “synchros” are made from a softer metal to ease smooth gear changes.
If your transmission won’t go into gear or pops out of gear once you’re driving down the road, it is probably a synchro problem, which could lead to other issues such as new shift forks, individual gears, and an assortment of internal bearings. Regarding cost, the range here is broad. One technician noted that he charges $800 for the rebuild of a manual transmission plus parts. He also noted that some gear clusters could cost up to $500 each. That can add up to big money, depending on the depth of the damage.
Automatic Transmissions
Automatic transmission issues are far more complex because these units contain about twice the number of parts and require careful assembly due to tight clearances and sophisticated electronics. The modern automatic transmission system contains a computer (Transmission Control Module, TCM) that connects to the engine control module (ECM). When your engine and your transmission are not working in tandem, you will undoubtedly know it through sluggish performance and a flashing or steady check engine light.
If your vehicle has a dipstick (some models don’t have this preferring to use engine diagnostics instead), you can check both the fluid level and its condition. Note the condition of the fluid on the stick. Red or light pink means it’s normal. Brown or black and smelling burnt means trouble. Enlist the help of a professional for further investigation.
RELATED: When Do I Need to Change My Transmission Fluid?
In general, automatic transmission problems fall into a couple of different categories from scary to easy. Let’s start with easy.
Automatic Transmission Problem Signals
- The vehicle is slow to move after putting the gearshift lever in Drive or other forward gear.
The first step is to check the level of oil in the transmission. In most cases, there is a separate dipstick that is close to the firewall (back of the engine) that commonly has a yellow grip. Pull out the stick, wipe it off, dip it in again, and read what it says on the dipstick. Here, you will commonly find the fluid level markings for the transmission and the type of fluid recommended. Check the transmission level with the engine warmed up. Make sure the vehicle is on a level surface and check the level with the engine running. Always check your owner’s manual for specifics.
If you don’t see a dipstick from under the hood, your transmission probably fills and drains via two ports on the side of the transmission near the fluid pan. You’ll most likely need to visit a professional.
If the fluid level is low, this could be your problem. The fluid is usually added through the dipstick tube, which doubles as a fill. It’s best to use a funnel when refilling the transmission. Spilled transmission fluid can cause a fire if it touches a hot exhaust.
Make sure the transmission is warmed up before you do the final assessment. If the vehicle is still slow to move when you press down on the throttle, it’s time to go to seek professional help.
- The vehicle does not move when it shifts into a forward gear
See above. In extreme cases, the fluid is so low the vehicle will not move at all. Check the level as noted before, add more fluid if needed, and then test again. Overfilling the transmission is also bad because it can cause the fluid to foam and reduce efficiency. If the vehicle doesn’t move, you need to seek the help of a pro. Issues that could be blamed in this case are the torque converter, the valve body, or dirt within the many narrow fluid passages within the transmission.
- The vehicle bucks and kicks when driving
In many cases, this is a very serious problem requiring a rebuild. If there is a diagnostic code, then a scanner will isolate the problem. It could be an adjustment, but more commonly it is a problem with the transmission’s internal clutches. Either way, a trip to the transmission shop is in order.
- The vehicle slows down despite pressing harder on the gas pedal
More bad news here. Again, the internal transmission clutches could be at fault, but another part, commonly called a “band,” can cause the transmission to slip and drastically reduce transmission efficiency. Other problems could point toward the torque converter (the literal heart of your transmission) or any of a cast of a thousand issues.
The sad fact about automatic transmissions, in general, is that they work great most of the time. But when they act up, 90% of the time it means internal issues you can’t fix in the driveway.
Use our Service and Repair Pricing Guide to learn more about transmission repair costs and to find a repair shop near you.
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