Transmission question with Protege

First, a little background. My college-age daughter drives a 2000 Protege with an automatic transmission and ~100,000 miles on it. During the summer she left it parked during the week, and only drove on weekends. She reports that it would have some sluggishness shifting from park into drive after that. Recently, she had an incident where when she first started it the overdrive light was flashing on and off, and it “wasn’t driving right”. She’s not particularly mechanically adept - her description of the problem is that when she stepped on the gas the engine would rev up, but the car wouldn’t accelerate the way it should. She said this was transient, and cleared up after a minute or two, and has not reoccurred. The sluggishness to shift into drive when cold is persistent, however. I took it to a local dealer for an assessment. They said 1.) they didn’t read any codes 2.) the transmission fluid level was fine 3.) that I should not have the transmission fluid changed because if I haven’t been doing this every 30,000 miles changing the fluid will loosen any deposits on the inside of the transmission and ruin it and 4.) that in their experience this constellation of symptoms means that the transmission is going to fail, and they offered to sell me a rebuilt one for $2600.

I’ve also discussed this diagnosis with my son, who’s the kind of car owner who doesn’t exactly buy cars - he buys car parts and assembles cars, so he has some experience. He asserts that the transmission fluid doesn’t look right to him and the dealer was incorrect about not changing it. He also pointed out that from the dealer point of view, they’d probably rather sell me a transmission than a transmission fluid change. So, in the experience of the readership of this forum, is it likely that the transmission is going out? Was the dealer right or wrong in discouraging fluid change? Is there some kind of sensor somewhere that could be the “real” problem? (As a further note, I’ve had my daughter park the car until we can deal with the problem, since as a typical college student she’s prone to driving around in the middle of the night and the dealer caused me to have some concern that it could fail and strand her in some bad part of town - so she at least feels some urgency about addressing the problem) Thanks in advance for any insight you might be able to give.

100,000 miles without the fluid and filter changed? Well, there is some risk in changing it so late (this is a subject of much debate on this forum), but if you’re looking at a possible rebuild anyway, what’s the harm? Can the transmission be flushed while you’re at it? Can a mechanic drop the pan and take a peek inside to see there are massive buildups of crud? If new fluid, filter, and any adjustments fix the problem, you’ve saved the cost of a rebuild. If it causes all the muck and crap to come loose and plug everything and you need a new tranny, well, you tried the cheap route first and it didn’t work, so time to pay the price for failure to maintain the tranny.

Your son is right. The transmission fluid should be changed, and if there is a filter, it should be replaced as well. Please note; I said “CHANGED,” not flushed.

DO NOT let anyone flush the transmission. Just have the fluid drained (removal of the pan may be necessary), replace the filter (if there is one), and refill the transmission with clean fluid. This may help. It certainly can’t hurt anything.

Flushing, on the other hand, may lead to rapid transmission failure, especially considering the mileage on this car, and the fact that the fluid has never been changed.

Change, yes. Flush, no.

Have the transmission fluid and filter changed as soon as possible. I’ve had a transmission exhibit symptoms of impending failure only to be rectified by new fluid and filter. Fluid that is old will wear our, lose viscosity, and additives in the fluid will be consumed and may even become reactive to form harmful acids. A clogged filter will breed low pressure throughout the transaxle hydraulic system.

Beyond that, sluggishness getting from Park to gear when cold is usually the sign of a bad anti-drainback valve in the torque converter. The TC must be FULL in order for torque to be transmitted form the engine to the transmission. If the drainback valve fails, the TC will drain out over a long period of time, eg. a few hours. It takes a few moments for the transmission oil pump to pump the TC back up and build up pressure in the transmission. If this is your problem, the engine should race when first put into gear after sitting overnight and the throttle is applied, and the vehicle should move very little to none at all for a few moments. Also, when the transaxle is first put into gear with the engine running after sitting overnight, there should be no noticible shock at all (the way a car normally jumps forward against the brakes when put into drive.)

Replacing the valve won’t be cheap because either the engine or the tranny will have to be removed. But if your son can pull engines, he can probably do this. The whole TC may have to be replaced, I’m not sure.

I’d suggest taking the car to an independent transmission shop and have them diagnose it. Be aware that you will have to leave it overnight. But if the tranny is shifting normally and only has problems getting into gear when cold, this is probably your problem and you won’t need to rebuild.

But if nothing else happens, CHANGE THE FLUID AND FILTER!!!