Car has had two instances of delayed shift into (2nd?) at beginning of morning drive over the last 6 months (once this morning while O/D Off light was OFF).

Last week the O/D Off light would be on in the morning, then fade away as car heated up during driving. Also rpms were high on freeway at around 60-65 mph (3000 rpm and no shift) all last week while O/D Off light was more or less on. Mechanic says no codes. Fluid is dark with red showing, level is fine. Mechanic says transmission is on last legs based on condition of fluid and shifting behavior, but no telling how long it's got.

The weather was pretty humid the last couple of weeks, but it has dried up a lot now. Radio was shorting at the end of last week. Yesterday and today the O/D off light hasn't flickered or come on at all. Radio is working normally.

My question is: should I leave things alone as mechanic says, or have the transmission fluid replaced (perhaps with some of the non-detergent type intended for old transmissions that I heard of somewhere)? I definitely don't plan to have it flushed. Bad experience there. Thanks for reading.

 

The car may have more then one problem, these being the transmission and the wiring.

When the O/D system is on the indicator light is off. There is manual push button switch on the center console or gear shifter that turns the O/D system (and light) on/off. When the switch is pushed the O/D light comes on and the O/D system turns off.

When the O/D system is off the torque converter does not lock up and as a result the engine RPM will be higher than "normal". This could explain the higher RPM's.

The O/D indicator light bulb ground wire goes through the switch stated above. The switch grounds the O/D negative wire to the chassis to turn the light on (and O/D system). There doesn't appear anyway to turn the light on other than to ground the negative wire.

Suggest checking for wiring or switch problems which could be causing the negative bulb wire to be grounded. This may be linked to the radio issue.

The transmission has several clutch plates ganged in a clutch pack. These plates wear out and more so with dirty transmission fluid. As to trans flush and problems there are a lot of theories. One is the debris in the dirty fluid is working as an abrasive to keep the clutch plates engaged. Another is a flush removes this "gripping" debris from the plates allowing them now to slip..

There many methods to change the trans fluid. Some use cleaning chemicals and or force the fluid through the trans sometimes backwards. The use of these methods can dislodge debris from the plates and trans. This debris can then also get into the trans shift module causing problems.

The safest method is to disconnect the trans fluid output line from the radiator trans cooler. This line would normally go back to the trans fluid pan. The fluid from the disconnected line is then routed into a container. The trans pan is drained and refilled with new fluid. The engine is started and the trans fluid pump moves the old fluid out of the trans to be replaced with new. Once approx 2 quarts comes out the engine is stopped and the trans pan is refilled with new and the process repeated. After 8-10 quarts the fluid coming out is now clear. This method places no extra strain on the trans.

A trans may be failing then the fluid changed and it sooner or later fails. One might conclude the fluid change was linked to the failure. An issue is not changing the fluid will guarantee a future trans failure.

Trans fluid breaks down with heat, the hotter it gets, the faster it breaks down. If the fluid is non-synthetic is might only last 50K miles.

Check the wiring which may solve the O/D issue. Consider the type of gentle fluid change stated above..