Is There A Fix For Auto Trans Wont Shift Into 4th Until Warm?

[bronsin]

Originally Posted by MadMax

There is no "fix" as there's nothing wrong with your transmission! It was designed to stay out of fourth gear until the engine has reached a certain operating temperature. It is for your engine's benefit and it would be detrimental to try to override the function.

Why would it be detrimental to the engine? A manual can be shifted into fifth immediately. Are people with manual transmissions having problems with their engines.

[MadMax]

Originally Posted by bronsin

Why would it be detrimental to the engine? A manual can be shifted into fifth immediately. Are people with manual transmissions having problems with their engines.

Not yet, but if they're shifting into fifth gear with a cold engine they might be doing unknown damage. It's well known that it's not good to go into OD when an engine is cold, and our little Yaris is smart enough to prevent the transmission from doing so. Why people want to override this excellent feature is beyond me, I guess they think they are smarter than the engineers who designed and built it!

[bronsin]

Originally Posted by MadMax

Not yet, but if they're shifting into fifth gear with a cold engine they might be doing unknown damage. It's well known that it's not good to go into OD when an engine is cold, and our little Yaris is smart enough to prevent the transmission from doing so. Why people want to override this excellent feature is beyond me, I guess they think they are smarter than the engineers who designed and built it!

I work with engineers who design proto type electronics for miitary and space applications. They design it I build it. Once we had 60 days to buiild the 150 circuit boards that went into a data recorder for a satilite. They put a software engineer in charge of the machine that built the boards. Under his direction they built 4 or 5 boards A WEEK. Because we would never get done in a year at that rate they put me running the machine on second shift. My first night on the job I built 14 boards all by myself. QC went apeshit in the morning. They thought they were all screwedup. Wrong.

When we went to surface mount electronic in 1994 the freaking genius engineers degreed we could not add flux to the parts before soldering. There is flux inside a hollow core and they said that was specifically designed by engineers whose shit does not stink to be all that was required. We assemblers were agast and just added it anyways. When some of us were punished for that we came to the realization we could screw them over by doing what they told us to do. The quality of the work was so bad they recinded their edit in a month.

That is the side of engineers you never hear about.

[sbergman27]

Originally Posted by MadMax

It's well known that it's not good to go into OD when an engine is cold

If I had a nickel for every "well known" bit of wisdom I've heard that turned out to be totally baseless, I'd be rich. So with my skeptic's hat on, I'll ask "how do we know this?". What evidence (as opposed to hearsay) can we point to?

I suppose what it boils down to is a assertion that a cold engines handle higher RPMs better than they handle higher torque, with respect to wear.

My Yaris is A/T. But my Chevy Sprint ER is a 5 spd manual. When cold, I shift at about the same points as I do when warmed up, getting into 5th at about 45mph. It would be interesting to know for sure what strategy minimizes wear.

-Steve

[Astroman]

Wow two pages and no correct answer why the transmission is locked out of 4th. It has to do with emissions (the cats need to be at operating temperature to work properly) and the quickest way to get them up to temp is by running the engine at a higher RPM. If your not going over 45mph why are you so worried about not getting into 4th for that short of a commute? My car only takes a mile at 30mph to get up to operating temperature, even when we were in single digits. Stop and go, tires, conditions, winter gas and other habits have more effect than not being able to get into 4th at 45mph.

[bronsin]

Originally Posted by Astroman

Wow two pages and no correct answer why the transmission is locked out of 4th. It has to do with emissions (the cats need to be at operating temperature to work properly) and the quickest way to get them up to temp is by running the engine at a higher RPM. If your not going over 45mph why are you so worried about not getting into 4th for that short of a commute? My car only takes a mile at 30mph to get up to operating temperature, even when we were in single digits. Stop and go, tires, conditions, winter gas and other habits have more effect than not being able to get into 4th at 45mph.

True probably that last part. But also it just bugs me the transmission will not shift into high gear sooner. How much better mpg would it get? Only one way to find out. Remember if it takes a mile to warm up and youre only driving six miles thats a pretty large fraction. I think putting a hot plate under the block for half and hour at 700 watts (about 7 cents at my rates for that time of day) might be more cost effective though.
Wait a minute...thats already patented isnt it? Dont they call that a plug in hybrid?

[sbergman27]

Originally Posted by Astroman

Wow two pages and no correct answer why the transmission is locked out of 4th.

In fact, I've mentioned emissions as a possibility. However, with all due respect, without a reference, your assertion is just another hearsay post.

As I've said before, given the same power requirements of the driver, there is no fundamental reason to think that the engine would warm up any faster at high rpm/low torque than at low rpm/high torque. Same goes for the catalytic converter. In the latter case, more air-fuel is packed into each cylinder, but the total amount of air-fuel/sec (and exhaust gas) is going to be about the same.

There may be other effects that make the higher rpm scenario advantageous. But I don't see any fundamental reason that it would be.

-Steve