Boston's Leading Mobile Mechanics

 

1. TRANNY REFUSES TO GO INTO GEAR

Shifting manually with a foot pedal and a "stick" gearshift is a simple operation.  There is something wrong if the transmission refuses to budge when you press the clutch pedal and attempt to move the stick shift.   This happen when you try to get into first gear - from a stop, or at any point up and down the assorted gears.   Common causes* include low transmission fluid, a wrong viscosity (thickness) of fluid, or a required adjustment of the shift cables or clutch linkage.

 

2. BURNING SMELL

If you smell a whiff of burning transmission fluid, it indicates that your transmission is overheating.   Transmission fluid not only keeps the transmission's moving parts lubricated, but it prevents the unit from burning itself up - by providing much-needed cooling.   In some vehicles, the transmission even has its own mini-radiator (oil-cooler) that circulates fluid to transport heat away from the transmission unit itself.   Common causes include low or inadequate transmission fluid, which can in turn indicate a leak or dirty fluid that needs changing.

 

3. TRANNY IS NOISY IN NEUTRAL

If you hear weird noises from the transmission while in neutral, it could be a transmission problem.   There is a simple and inexpensive solution -- as with many of the problems on our list, adding or replacing the transmission fluid sometimes does the trick.   Alternatively, lots of noises from the transmission while it's in neutral could signal something more serious, like mechanical wear that will need the replacement of parts.   In this case, common culprits are a worn reverse idler gear or worn bearings, possibly coupled with worn gear teeth.

 

4. TRANNY GEARS ARE SLIPPING

In a normally functioning transmission, the car stays in the gear that you chose, or that the computer designates for a given RPM range -- until you or the computer initiate a gear shift. But on a transmission in which the gears slip, the car can spontaneously pop out of the gear it's in while driving and (in a manual) force the stick back into neutral.   This is unnerving at best and potentially dangerous at worst.   When you step on the gas pedal to avoid an out-of-control vehicle, the last thing you want is a transmission that doesn't get power to the wheels. If this happens, it's time to have the transmission examined.

 

5. DRAGGING CLUTCH

Another transmission trouble that haunts manual transmission vehicle owners: the dreaded dragging clutch.  A dragging clutch is one that fails to disengage the clutch disk from the flywheel when the driver pushes in the clutch pedal.  When the driver attempts to shift gears, he cannot because the still-engaged clutch is “still spinning” along with the engine.   The driver is made aware by the grinding noise that ensues with each attempt to shift.   The most common cause for this problem is not severe or costly to fix.   More often than not, the problem is too much slack in the clutch pedal. With too much free play, the cable or linkage between the pedal and the clutch disk doesn't have enough leverage to disengage the clutch disk from the flywheel (or pressure plate).

 

6. LEAKING FLUID

Leaking transmission fluid is one of the easiest to identify that the transmission needs attention.   Automatic transmission fluid is vital to the car, so a little fluid on your driveway can quickly turn into a major problem.   Automatic transmission fluid is bright red, clear and a little sweet-smelling when everything's working correctly.   To check, make sure it's not a dark color and that it doesn't have a burnt smell.   If not, you need to have it replaced.   Unlike a car's motor oil, the transmission doesn't really consume or burn up any fluid during use, so if you notice you're running low on fluid, then it's definitely leaking out somewhere.   If you have manual transmission, checking the fluid level may not be as easy as lifting the hood and reading a dipstick.   Manual transmission fluid has to be checked right at the transmission case -- usually through the fill plug.   If you suspect your transmission is losing fluid, have it fixed.

 

7. CHECK ENGINE LIGHT

If your fluid level is good, there's an easy way to know if there's something wrong with the transmission -- without even having to pop the hood.   The check engine light can be a great early indicator that something is starting to go wrong with the transmission.  

In newer cars there are sensors throughout the engine that pick up irregularities in the engine and notify the computer that there's something wrong in a particular area.   In the case of transmissions, these sensors pick up vibrations and early problems that you may not feel or see.   You may purchase a diagnostic scan tool that plug into your car underneath the driver's side of the instrument panel.   This scan tool will display a code that corresponds to the area of the vehicle causing the fault.   If the code tells you there's a transmission problem, that's a good time to see a mechanic.

 

8. GRINDING OR SHAKING

Depending on whether you have a manual or automatic transmission, your car may respond differently when your transmission isn't working correctly.  

With a manual transmission, a common sign of trouble is a grinding sound or feeling when you shift into a new gear.   If you fully engage the clutch, shift and then hear a grinding sound, you may have a worn clutch or you may just need to have it adjusted.   One of your transmission's gear synchronizers, or synchros, may be worn out or damaged. 

 

For automatic transmissions, you'll feel the car shimmy into each gear rather than the typical unnoticeable shifts, or the transmission will make a jarring transition into the next gear.   Both are signs that the transmission needs attention.   If you notice anything other than a smooth transition between gears, then you need to have your automatic transmission looked at for adjustments or repair.

 

9. WHINING CLUNKING AND HUMMING

It's difficult to know exactly how a car may sound if there's transmission trouble, but you'll probably get a that-doesn't-sound-right feeling when you hear it.   Every car is built differently, so the sounds they produce can vary greatly, but if you have an automatic transmission, you may hear a whining, humming or even a slight buzzing sound.

 

With manual transmissions, the sounds will come across as a bit more abrupt and mechanical sounding.   If you shift gears and hear a clunking sound, then you need to have it checked-out by a professional.  

 

A clunking sound from underneath the vehicle may not always be a transmission problem. The constant-velocity joints (CV joints), or the differential may be the culprit.   The sounds you hear may happen from time to time - at first, but if you neglect the noises, they'll occur frequently as time goes on.

 

10.  LACK OF RESPONSE

Transmissions are designed to go into the correct gear every time, so when they hesitate or refuse to go, it's a sign there's something wrong.   With manual transmission, you may notice after shifting into a gear that the car's engine will rev up, but the car won't be moving as quickly as the engine is running.   In this case, a worn-out clutch or a more serious transmission problem may be occurring .  

 

Automatic transmissions have the same lack-of-response, but will usually manifest the issue while engaging the "Park" or "Drive" selection. The car should shift quickly into either of these modes, but if the transmission hesitates to go into either one, then it's likely there's an issue with the transmission.