HarrierRX300

Hello,
I was wondering when do you use the OverDrive Off button on the shifter? Do you normally drive with OD off or just on steep hills? Just wondering. Thanks.

Lexmex

I used it at the track with the PWR button on (did enough tests to see a small advantage).

Othewise as you mention I use OD/off on hills.

mmarshall

Depends on if it's a car or a truck. With a regular car or a small crossover vehicle, the best time to use it is on moderate hills, going up, under conditions where you don't want the engine lugging or the tranny shifting back and forth between the top two gears repeatedly, or going down, to get engine compression to keep from having a heavy load on the brakes.

With a truck or SUV, sometimes you have a TOW/HAUL mode button on the shifter that does essentially the same thing...it locks out overdrive for towing heavy loads.

Keep in mind, though, that the OD OFF and TOW/HAUL mode switches trade road speed for extra power and compressional braking, so you have to drop your speed some when you do use them, especially at higher road speeds where you could red-line the engine by downshifting...sometimes the computer will block them out when that would happen. And, in general, the more gears you have in the transmission to start with, the closer the ratios will be, and the less the RPM drop will be when the overdrive downwshifts into the next lowest gear....and the less you will have to slow down.

Also, some of the newer automatics have a "Grade Logic" feature in them which, without any driver input, is supposed to detect grades and keep the tranny from upshifting. Some of them work more or less like they should, some don't....the feature, in general, doesn't impress me. I've found by experience that driver control of an automatic on hills is usually best.

ff_

On our '06 ES, we don't have an OD button, but can obviously shift down into the lower gears manually. This car tends to race and see how quickly it can get into top gear, regardless of where or how fast you're driving. The problem is that in top gear, the revs loaf way too low, and results in poor mileage around town, and the frequent need for downshifts. And downshifting is something that this Lexus is very bad at (terribly slow delay, and very reluctant to even change gears in the first place). So I always keep it in 4th gear until I'm out on the highway. This solves all the problems I listed above, which makes me a more happy driver.

HarrierRX300

Thanks for the info. One last question. Is that the same as "Trac Off"?

mmarshall

No. TRAC OFF has nothing to do with transmission gearing. It disengages the traction control and stability systems, if the vehicle is so equipped. Usually it is a button or switch on the dash or console. Under normal driving conditions, there is almost no reason why you would want to turn those systems off in the first place, especially on slippery roads......they are put there for your safety, and to keep the wheels firmly in contact with the road.

Because they generally power the engine back and apply one or more of the brakes when the tires lose traction or slide, aggressive drivers and some of the "enthusiasts" in the auto mags like to turn the systems off so they can do burnouts, drifting, and powerslides, which, IMO, are not only dangerous on many public roads, but can grossly abuse the vehicle as well.