1. The first thing you should do when you suspect you any transmission problem is to check the transmission fluid level & condition. The engine should be running with the transmission
in “PARK”.  Check information on dipstick as some transmissions are checked in neutral.

TIP: Always insert the dipstick 2 or 3 times, look at both sides, and check for a consistent reading.  
                                                    
2. If the fluid is low, fill to the proper level & test drive the vehicle.

If the abnormal symptoms are gone, your primary problem is a leak.  Continue to monitor the fluid level, add as appropriate, and have the leak source diagnosed before additional problems occur.

A Slow leak is worse than a big leak! A slow leak will allow the transmission to operate until the  level is low enough to subject the unit to low fluid operation which will cause excessive wear! 

A big leak will certainly get you attention & usually results in little or no internal damage.

There are numerous transmission seals, gaskets and o-rings that can leak. Therefore, a visual inspection is necessary to determine leak sources before an estimate for repair can be made.

1. Check for any transmission linkage, vacuum hoses or electrical connections that may be loose or disconnected. One of the most common problems are corroded battery terminal connections.  Clean terminals are particularly important for late model computer controlled transmissions.

2. The follow is general information regarding computer controlled transmissions.

Late model transmissions are controlled by a computer that operates shift and pressure control solenoids inside the transmission.  Therefore, the computer needs to be electrically scanned by a transmission professional to determine if any electronic control problems exist.

 

When the computer “sees” any parameter from various sensors that do not fit established criteria, the computer sill set a code for the error, which will be evident by a “check engine” and/or a flashing overdrive light. 

NOTE: There are some errors that will be present that the computer does not sense because they are within the normal range. In that case, the system has to be diagnosed to determine if applicable sensors or other electrical components are performing incorrectly & creating an abnormal transmission operational response.
    
The following sensors are usually part of the transmission:  MPLS (Manual Linkage Position Sensor), input and output speed sensors, shift solenoids, Governor sensor etc.

Please be aware that some sensors are not part of the transmission itself, but in other areas of the vehicle. These include: the TPS (Throttle Position Sensor),  the MAP (Manifold Absolute Pressure Sensor), PCM (Power Control Module or Computer Sensor) IAT (Intake Air Temperature sensor) etc.

Also, be aware that a scan done at a “parts store” will not show all the information necessary to form a conclusion about an electrical control problem.  A lot of problems in the control system do not set a code in the computer, but can still cause transmission problems.

When the shifts of a computer controlled transmission are excessively firm, the pressure regulator  may set to maximum pressure by the computer if it senses a problem from one or more sensors.

The result of diagnostic testing should indicate whether the problems are in the control system, the transmission, or both.
     
When the ignition key is cycled, the computer is reset and will control the transmission normally until an error is registered.  Then the transmission will be placed in “limp” mode (2nd gear) again by the computer.

I’ve found that it is much better to evaluate the situation “hands-on” than to speculate on the phone.  Over the years, I’ve been amazed at the number of times the conclusion made before seeing a vehicle changes after it is inspected and the situation diagnosed.

 

For further diagnosis, repair, or a second opinion, call us at (719) 522-1117

Barry Remple
Colorado Transmission