[kjarrett]

This is my first Toyota and I don't know what's normal ... but I was reading this thread:

http://rav4world.com/forums/viewtopic.php?t=1903

and I understand that a warmup period of between 30 seconds and a minute or so is probably sufficient depending on ambient temps.

Anyway, I've noticed that even with a warmup of about a minute on mildly cold mornings (0 celsius here so far) the trans takes about a mile or so to warm to the point it will shift into OD. My questions:

Is this normal?

I've told my wife (who does most of the driving) to take it easy until the car shifts into OD but should I be concerned about this?

Will a longer warmup make an appreciable reduction in the time it takes to get the tranny to operating temp?

Thanks, kj

 

[bmorton]

Normal for all automatic transmissions. When coolant temperature is lower than a preset figure, driveability could suffer if the transmission was allowed to shift into overdrive or the converter clutch was locked up. The ECU monitors the coolant temperature and won't allow the transmission to shift into overdrive or lock up until the coolant reaches the preset temperature.

I prefer driving to warm the car up evenly so I just take it easy for the first few minutes.

 

[kjarrett]

Understood, thanks.

Would a longer engine warmup make an appreciable improvement in the speed that the tranny comes up to temperature, vs. just driving?

My wife is my concern ... I tell her to take it easy when the car is cold but if the kids are late for school or she's got to accelerate hard to get out of our neighborhood onto the main road ... just wondering how much damage we risk, and, how to mitigte.

When I drive the car I always take it easy when it's cold out, allowing the TC to lock up.

-kj-

 

[nouse4aname]

I don't generally let a car sit and warm up. But I don't like to take any car much above 3k before reaching operating temp.

Suppose if you're really concerned about it you could get an engine block heater.

Here's a good little 'did you know?' article on idling.
http://oee.nrcan.gc.ca/communities-...-communities/articles/idling-tips.cfm?attr=28

Once a vehicle is running, the best way to warm it up is to drive it. With computer-controlled, fuel-injected engines, you need no more than 30 seconds of idling on winter days before driving away.

Warming up the vehicle means more than warming the engine. The tires, transmission, wheel bearings and other moving parts also need to be warm for the vehicle to perform well. Most of these parts don't begin to warm up until you drive the vehicle away.

Excessive idling can be hard on your engine. Because the engine isn't working at peak operating temperature, fuel doesn't undergo complete combustion. This leaves fuel residues that contaminate engine oil and make spark plugs dirty.

It's important to drive away as soon as possible after a cold start. But avoid high speeds and rapid acceleration for the first five kilometres. This lets the whole vehicle reach peak operating temperature as quickly as possible without paying a fuel penalty.

 

[RAV4Don]

bmorton and nouse4aname are correct.

I believe Toyota has programmed the PCM not to allow shifting into OD to occur until the engine reaches a prescribed operating temperature thus improving reliabilty issues with the engine and tranny, but also to reduce emissions. The engine warms up faster (and reduces emissions conditions quicker) at the higher RPMs found in remaining in a lower gear at higher road speeds.

Wifey's Lexus does this. I found it annoying also, until I reasoned why it was designed this way.

 

[kjarrett]

Thanks, 'twas what I suspected. As long as it's design behavior, I'm cool with it. -kj-

 

[bmorton]

I guess the answer to your basic question would be yes, if not being able to shift into overdrive immediately after driving away is the greatest concern, you could idle it longer to bring the water temperature up to the point where the ECU will allow overdrive to kick in. It's not the transmission the car wants to warm up so much as the engine. How long you'd have to idle in order to warm up the engine sufficiently is another question.