lexus_mark

What is the purpose of the O/D button?

LexRX

It is basically like shifting your tranny from 4th to 3rd hear or vice versa. Many (4-speed autos here) transmissions have D-3-2-L. The RX, instead, has D-2-L. If you are towing or want to manually downshift the RX's tranny into third you would take it out of OD (overdrive).

CK1_RX3

So to expand on that, it's good for engine breaking and for a quick downshift for fast accleration if you're already going about 40-55 mph and want to pass someone/merge, etc... However, as for the acceleration part of that, the RX's computer is pretty fast to downshift for you in the situation that you step on the gas hard...

LexRX

Also, when towing, taking the vehicle out of O/D can be a good idea to keep the vehicle from shifting into 4th gear. That way the tranny doesn't continually shift in and out of 4th, especially on hills. This is basically what GM's slightly more sophisticated "Tow Haul" mode does on their trucks.

Also, as a general rule for engine braking, I don't ever manually downshift an automatic. Brakes are cheaper than transmissions..engine braking is fun though!

FCobra94

I find it usefull in city driving when you don't really spend any time in 4th gear anyway...it's a good way to lock it out and keep it from unecessarily upshifting...power is also there quicker and I'd say it's probably a little easier on your tranny as well

CK1_RX3

I agree! I drive the same way in the city - leave it in third... That way acceleration and power is right there when you want/need it, and it's easier on your tranny because it isn't shifting constantly. Probably hurts mpg a bit, but that's not really much of a concern.

LexRx - I don't think it's too much of an issue to manually downshift... The transmission in the RX is rather rugged, and while you're right that replacing breaks is cheaper, I don't really think you're going to do any real harm so long as you use good common sense when manually downshifting... Even beyond that the computer won't let you shift into anything that's really going to cause too much wear on the engine or the tranny - if you're going to fast for 3rd gear/2nd gear/1st gear, it won't let you downshift...

cephraim

On a related subject - do people find the ECT (?) mode useful?

CK1_RX3

DEFINATELY. Depends on the year of vehicle you're talking about. I believe '99 and earlier the ECT button consisted of 3 settings - normal, "ECT POWER", and "SNOW"... Snow is an obvious one, and ECT power is preferred if you enjoy quicker acceleration, as it causes the transmission to wait longer in downshifting on hard acceleration... True, your gas mileage will decrease, but I think it's a good trade off personally, and I ALWAYS left ECT on with my '96 ES300 and my '90 ES250.

On the '00 RX3 the ECT mode became a bit more "intelligent" if you will... There is still a button to put the vehicle in "SNOW" mode when the conditions require, but the "POWER" mode part of the button is gone... This is because the vehicle's computer senses the type of driving you are doing at a given time and selects the appropriate "normal" or "ect power" mode for you... It is nice because it results in improved mpg when you're not really driving hard and fast, but the compromise is that it takes a second to kick in the ECT power if you really step on the gas to pass someone, etc.

This topic has been covered before, and you might find more about it if you do a search, but this is what I know... Hope that helps -
ck

LexRX

CK1_RX3, the '00 RX still has both POWER and SNOW modes. Lexus didn't get rid of the seperate POWER mode until '01.

I'll have to agree that they are useful. I found SNOW mode especially useful on Jan 1, 2001. I drove on a freshly snowed roads (less than an inch, but the ground was fully covered). SNOW mode made accelerating from a stop much easier - it basically prevented a whole lot of wheelspin...as did the traction control.

CK1_RX3

Right on LexRx - Snow mode does EXACTLY what you described... controls acceleration at all wheels for maximum traction... It's useful in everything from really heavy downpouring rain (although not absolutely necessary there), to those famous Wisconsin snowfalls.