No 'Overdrive' after Changing Transmission Fluid

I didn’t catch the type of car involved but I have a suggestion that is very simple to verify. I had 2 Toyotas (circa 1989 and 1995) where the automatic transmissions had a ‘normal’ and ‘power’ mode – you pushed a button (it was an ‘in/out’ toggle) and in ‘power’ mode the transmission stayed out of overdrive, and also shifted at different speeds/rpm’s to give you more power. This sounds exactly like what the woman described. In one car the button was on the center console; in the other car it was on the shifter knob. It could be that when the transmission fluid was changed they intentionally or inadvertently pushed the button to the ‘power’ position. Or the driver pushed it…coincidentally. You can check around your console or shifter knob, or read the owners manual, to see if the car has this option. Toyota called it ‘ECT’ - Electronic Control Transmission. Other makes may have had this feature too and called it something else. Before you pull the pan down it’s worth checking. Best case you just push the button in or out to get out of ‘power’ mode and back to ‘normal’. Good luck!

I recall some of the F-series trucks we had on our family farm having this feature, but I understood it to be an advantage for when you’re towing something. If I remember correctly, it was just a button on the gear selector lever that prevented the transmission from going into overdrive.

As far as I know, all four-speed automatics have that feature. The switch can be on the dash, or on the console, or on the shift lever. HOWEVER, once the ignition is switched off, the switch is inactive until pushed again, with ignition on.

Good suggestions about the overdrive lockout switch - maybe the mechanic disonnected it inadvertently.

I had a 1988 Olds Delta 88 that I changed the fluid every 30K miles. At 100K it quit shifting into overdrive, but there was no switch on this car. I added 2 oz of an additive called Militec, claimed to be a friction reducer, which solved the problem then and at every subsequent trans change. I sold the car with 170K and the trans was still working great.

My point is that if it isn’t the lockout switch, try something to make the fluid more slippery, like an additive that claims to cure shifting problems.

Tom, Ray, love the show. I know you have a different opinion on this, but it happened to me years ago. I asked the shop to replace the rear seal in my '57 Chevy 283 engine, but they replaced the rear seal in the 2-speed automatic transmission instead. The transmission went out after about 3 days. None of the gears worked.

The explanation I heard then (as an engineer and shade tree mechanic, it makes sense to me) is this: Automatic transmission fluid should be changed every 20,000 miles. But if it goes 40,000 miles without changing, then never change it. The problem is that after the detergent in the oil is completely saturated, then dirt and debris gets caught in all the stagnation points, which includes the gaskets and seals. When you change the oil, fresh detergent cleans out all the grit and grime that was making the seals tight. When the seals are clean again, they can no longer maintain pressure, so they begin to leak. Particularly the piston seals that actuate the bands. If the bands do not work, the car will not shift into that gear.

If the lady continues to drive the car, it will not only lose overdrive, but all the other gears in turn, as the bands stop working. Yes, it can be fixed, but only by replacing all the seals. The cost for my '57 Chevy was $400 bucks back in the 'sixties.

Wow, that urban myth just won’t go away.

Re: Joesshadetree. I heard it a little different. Tranny fluid should be changed at manufacturer recommended intervals–usually 35k. But if it isn’t changed for a very long time, the detergent in the fluid breaks down and debris, gums and varnishes form in some places. If you subsequently change the fluid, the new fluid with fresh detergents can wash these deposits loose to form clogs in the tiny transmission passageways and cause the tranny to malfunction. Alternatively, with this lady’s vehicle, they may have changed the fluid by pumping it out through the transmission dipstick tube and refilled it that way, leaving the filter, already pretty filled to become clogged with debris released by the new detergents in the new oil.