Transmission Overdrive

I have a 1997 Ford Windstar GL with a V6 3.8 engine. The transmission was overhauled and works fine except that it goes in and out of overdrive for a second or two seconds. The Transmission shop has replaced the electronic lockout or lockup and other electronic stuff on the transmission, but it still goes in and out of overdrive. The tach goes up a little and you hear a sound. The engine had a tune up with new plugs and new plug wires. The engine mechanic says its the transmission and the transmission shop says it the engine causing the problem.

My money is on the transmission, Windstars have a storied history of transmission problems (To be fair they have a storied history of head-gasket problems as well, but I don’t think that’s the issue here.) When the transmission was ovehauled what exaclty was done to it? Did they replace the torque converter with an uprated one?

Yes, the torque converter was replaced.

If the engine or the transmission are acting up, the fault should be stored as a trouble code in the computer. Did you get a trouble code read-out?

No, the computer shows no code. The trans mechanic hooked up a computer and drove the car and it showed the tach was correct about going in and out of overdrive. The engine mechanic said that the reason there is no code that the problem is within normal range and the computer does not consider it to be a problem. The van is getting 24 mpg on the highway which is what it got before the repair of the transmission.

One of the things that disengages the overdrive is when you step on the brake pedal. Have them check if there might be a problem with the brake switch.


I think that may be the problem because when I hit the brakes sometimes I hear a noise from the rear drum brakes. I will have the brake switch and the brakes checked out and see if my problem goes away. Thanks, Hambruce

OK, first of all, is it coming out of overdrive or is it coming out of lockup (TCC)?? Big difference here. Second of all, you said they hooked up a scanner, what did the scanner show?? Is it showing the computer COMMANDING the shifts in and out of O/D or lockup?? You said they changed the lockup solenoid but they are troubleshooting an overdrive issue. I’m kind of confused here.


The scanner showed it going in and out of lock up. The Trans. Shop has replaced the electronic lockout more than once and it still does it. The Trans. Shop rebuilt the trans. when I first bought the vehicle and I have put over 100,000 miles on the trans. before being rebuilt again.

You could be dealing with a bad converter itself. I have got bad converters before myself right out of the box. I’ve had some that wouldnt lock up, I’ve even had some which were welded wrong and had so much runout it destroyed the pump and burned up my rebuild. Thats a possibility. Other possibilities are electronic in nature, TPS, Coolant temp Sensor, Brake light switch, trans temp sensor, pressure sensor. This should be something the trans shop should be troubleshooting. Was it doing this before this last rebuild or is this something which just started happening??


The transmission did not have a problem with lock up before now. The Trans. Shop has replaced all the above mentioned things except brake light switch and Coolant temp Sensor. I am going to have a mechanic checked that out for me. Thank you for your suggestions and help.

If your OD switch is on the end of your shift lever, I have found the little wire chaffing where it comes through the steering column and goes into the groove build into the shifter lever. It is all covered with plastic/rubber, so until you tear it apart, it’s hard to see the cut/chaffed wire. Just something else to check if you’re still looking for a cause.