what would happen if I turned ovedrive off??

Question

I have a 2000 Mercury Grand Marquis with the Ford 4R70W transmission with overdrive.. If Im driving at a constant 60 miles an hour on the highway what would happen if I turne overdrive off? If I'm gongi 90 miles an hour with overdrive off could i damage the tranny or the engine??

Answer 1

Nothing will happen at 60mph. Your RPM's will go up a couple hundred and the associated engine noise will increase. At 90 there still shouldn't be a problem unless you hit the rev limiter while doing it. I'm not sure where the RPM's are on that vehicle at 90mph or where the rev limiter is but the worse you will do is hit the button and the engine will shut off until its back under its "safe" limits. If you tow anything with that car I'd take the overdrive off. I sometimes do this in my truck while driving up steep grades rather than force the truck to downshift.

Answer 2

Where do these guys get these ideas???? Cars ran for 50 years without OD units factory installed. The answer is no, it will not hurt anything, burn up the transmission, or blow the engine. You have a 22% over drive fourth gear. Turn it off at any speed and the transmission down shifts to direct drive, and the engine speeds up around 22%. You still have lock up converter, so heat build up is minimal, just due to faster speeds in the tranny. Your gas mileage will suffer by around 15-20%. AT 90 MPH your engine rpm will only climb to around 3500. Yes, the car will feel more responsive, but just floor it and it will drop out of OD anyway. Yes, the car does slow down better with engine braking, but not because OK allow freewheel, it is just that mechanically, the OD does not use engine braking as well, exactly the same as down shifting from third to second.
Good Luck

Answer 3

I have a 2002 Grand Marquis with a floor shifter and the overdrive button is on the floor shift. Turning the overdrive off will actually feel like you have more horsepower because it puts you in a lower or normal gear. If I take the overdrive off the RPM's go up and of course you burn more gas. You can drive around with out the OD and the car would act just fine. I do suggest you not turn it off and on at high speeds because you can burn up the OD and don't have your foot on the gas when switching it off or on.

This applies to all new cars with Overdrive:
I turn off the OD when in heavy traffic because it lets the car slow down on its own where OD causes a car to coast and not downshift automatically. Also shut off the OD in rain or snow so the car can downshift on its own, with the OD on it will coast and not downshift. If you want more HP then turn it off but you burn more gas.

If you have a standard Marquis you probably have single exhaust they are not the fastest, the dual exhaust cars are more responsive and a few more horses.

Answer 4

you will not damage anything at all. At 90 the computer can tell if the 0d is off, be honest with you, that idea came into play in the late 80s and early 90s for the police packaged crown vics. at high speeds crusiers got better performance with the od off. the best place to turn it off is in town when going 30 and 45 miles an hour it is easier on the transmission this way your tourque converter is not engauaging the od. At 60 you will not do damage, just throw it out the tail pipe by burning more fuel

Answer 5

I'm pretty sure your car is a 4 speed, so turning overdrive off would only allow you to make use of the first 3 gears. Your gas mileage would suck and your engine speed (rpm) will be much higher. If you did 90 and turned it off, it would probably cause some damage and your rpms would shoot wayyyyy high up. But im not positive, because i don't know your 3rd gear ratio and the maximum speed that can be reached in that gear.

edit** turning OD off to slow down is a BAD decision, using the the torque converter's ability to brake in an automatic transmission can overheat the fluid that causes a torque converter to work (if you know how one works then you will understand why).

Answer 6

If you turn overdrive off, you will not have the 5th gear anymore, so the rpms will shoot threw the roof, it would cause damage to both transmission and engine. If you could even get the car up to those speeds in 4th gear.

Answer 7

Listen to drag1line and flh-ryder, these guys know their stuff. The others....well at least they're well intended. I second the latter's reccomendation, don't worry about it unless pulling a trailer or up or down steep mountain grades. Going up the engine will spin faster and be less labored and going down it will help slow the car and save on your brakes and possible overheating of the brakes.

Answer 8

Automatic transmission.......... AUTOMATIC ..... being the key word.....leave the OD on and let the tranny do what is was designed to do....You gain nothing by switching it off....but you will lose gas mileage by running around in 3rd gear constantly....if you need more acceleration pushing your foot to the floor will automatically shift it down to 3rd gear....only time it's recommended to turn it off is if you are hauling a heavy load...as in a trailer......consult your owners manual if you have one.

Answer 9

You could overheat the transmission by driving with the overdrive off for long periods of time. Your not going to blow up your engine by downshifting to drive @ 90mph. You could put it in drive and hit your governor and still be well below red-line.

Answer 10

I'd have the police at my door, an APB out on me and there may even be a missing persons report filed... All within an hour. I resent my cell phone because it feels more like a homing device sometimes.