mmarshall

I sometimes get questions from people who complain that their automatic transmissions, during cold warmups, delay upshifts past the first couple of gears, if this is normal or not.
Rest assured......in most cases, it is. Many (in fact most ) newer torque-converter automatics and, in some cases, automanual DSG/SMG have temperature-sensors in them that, on a stone-cold start, restrict normal shift to only the lower (or non-overdrive gears) until the engine coolant and transmission fluid reach a certain level...which, in many engines, is around 140 degrees. At that point, engineers generally consider an engine or transmisson fully warm for fluid-circulation and engine-stress purposes (this is usually at the lower end of the normal range on an analog temperature-gauge, or when the blue cold-engine light goes off). Another reason, of course, is to heat up the catalytic converter(s) more quickly for better emissions at low temperatures.

However, I agree with those who find this feature somewhat annoying...I also do myself. Most of the more recent automatic-equpped cars I've owned were like this, though the Subaru Outback I had (fortunately) seemed to lack it. It obviously raises the engine RPMs during cold warmups, increasing engine noise and fuel-consumption (at a time when you generally don't want the engine to be spinning fast because of internal-friction), so, until the computer allows the upshifts, you have to keep your speed way down while impaitient drivers behind you (they seem to be legion these days) also get annoyed. This up-shift blocking generally occurs in both full-auto and auto-manual shift mode....if trying to do it manually, you will either get a computer beep-beep (which means a no-no), or a "Shift-Denied" message on a screen.

I understand why the engineers have done this (for faster warmup/emissions purposes), but I'm still not really sure if it's otherwise a good idea. As stated above, it increases cold-engine-wear and friction inside the engine and transmission by forcing more RPMs than is necessary during warm-up (though the reverse arguement, of course, is that the engine itself warms up faster by doing so). And, by blocking out the overdrive gears (and sometimes even some of the non-overdrive gears), It makes one drive slower than necessary during the primary warm-up stage (where you usually don't want your engine going over about 3000 RPM or so)....sometimes with impaitient drivers behind you.

This, of course, is usually much more of a factor in winter, because in summer the warm-up times are usually much shorter.


Is it the worst feature on newer cars? IMO no, not by a long-shot. But I won't go into those features I find even more annoying (that is not the purpose of this thread)

geko29

The 6-speed in my 335d does this, and it bothers me enough to put it in manual mode on cold days. In casual driving, it typically should be upshifting around 1600-1700rpm. When the temp is in the 20s or below, it'll hold 2nd gear until 2300 or so, which is supremely annoying (remember, this is a diesel, so the shift points are much lower).

Luckily, it doesn't block me from upshifting, it just won't do it on its own. After 4 minutes or so of driving, it returns to normal.

2GSKaizen

iTrader: (1)

I hear what you are saying. I see a lot of newer cars that do this. I really don't understand what you are saying about the internal friction stuff though. Metallurgy has come so far just in the last 10 years, as well as lubrication technology. I really don't think the internal friction could be that much higher upon a cold start. I don't for a second doubt that it is higher, but I think the metals they use in these new engines is so much less resistant to expansion and contraction due to temperature. I think they say your pistons and rings have fully expanded within the first 30 seconds or so of running. I don't know though. I think the main reason they do this is because of how much higher the pressures are inside the transmission valve body when the fluid are cold. With those pressures elevated so high I think it's just the limitations of the spring controlled valves in the valve body not being able to accurately control the shift timing and harshness. The only way to combat this is to get the fluid warmer, faster. Higher RPM driving is really the only way to achieve this without using transmission fluid heaters or something. I guess I'm one of the 1% that ALWAYS start my car and let it run for at least a minute or 2 or 5 depending on outside temperature. I drive a little "spiritedly", so I'm always sketchy about that 1 in 1,000,000 chance that i could spin a main bearing, or throw a rod through my oil pan when its cold.

Hoovey689

iTrader: (16)

Yup, I live 30sec off the freeway. My IS350 will not shift into 6th gear until the engine temp gets to about 1/4 warmed up

mmarshall

6th, on most IS models, is a very tall overdrive, so, if it at least allows you into fifth, that shouldn't affect things much.

On the old IS300 models, though, with the short-geared 5AT (I owned one), It was a different story. It wouldn't go out of third until almost the normal range...and, if it was really cold, even held it in second for the first minite or two. Of course, if it is really cold, you don't want to shift into gear to start with until the temperature and oil-pressure have come up at least a little.

SteVTEC

My 335i does this, as does our X5d, as did my Toyota RAV4 V6, as did our 2002 Toyota Highlander....

FrankReynoldsCPA

My 92 LS does this and it annoys the hell out of me.
This is my first automatic transmission, and I anticipate returning to a manual.

TangoRed

Every car I've owned does this and it doesn't matter to me one bit. I too live less than a minute off the highway; even worse, it's an uphill ramp. No matter how cold it is, I hit 3k RPM's in 5th gear in my E60. It'll be fine.

Hoovey689

iTrader: (16)

That's true. I have an exhaust and a midpipe so it gets a little loud in the morning's when it's stuck in 5th lol

Fizzboy7

I agree with MM, logically thinking, it seems the higher rpm's go against everything we were taught about keeping rpm's low when the engine is cold. My IS250 does this and it is definitely annoying. When cold, my car will not shift passed 3rd gear when driving on a typical city side street. This is whether I'm in manual or automatic mode. However, I've always assumed the engineers factored this in for a reason, so I let it be.

FrankReynoldsCPA

Yes, but it depends on who the engineers have in mind when they engineer that.

In this case it seems to be for the EPA at the cost of the consumer.

We've seen this in the diesel emissions with the addition of the Diesel Particulate Filter back in 2007. The big 3 had to install filters on their diesels which collected the soot, and when that fills up, they have to burn it off. They programmed an injection event to occur during the exhaust cycle so that the hot fuel would burn the soot into ash through the exhaust. The side-effect of this terrible piece of equipment was not only poor MPGs, but you have fuel entering the cylinder during decompression, and the fuel gets past the rings and into the oil, causing premature damage to the engine. But the EPA doesn't care.


Not all things are engineered into our cars for our benefit.

Lil4X

I recall discussions of this on the RX300 forum ten years ago or so. The official reason from Toyota was, if I remember correctly, to allow the engine to rev slightly faster in order to get the exhaust gas temperature up quickly enough to light off the cats. It was an emissions feature to meet federal mandates and was programmed into the ECT.

My 300 in cold weather required about 3/4 mile before the shift pattern fell back to normal, so it was not a long period of retarded shifts, but one that was troubling nonetheless. In sub freezing weather, it took about a mile before the transmission shifted normally. The difference was only about 500-700 RPM, so it was not really significant as far as wear was concerned (today's low-viscosity lubricants bathe all critical moving parts in oil long before you can get out of your driveway). It did make a considerable difference in the sound you anticipate when driving, as the shift point, particularly at 2-3 seems to hang up interminably.

By 2004, the RX330 seemed to have solved this effect, either by reprogramming the tranny or improving the sound insulation.

Of course, this assumes you follow the Owner's manual and take it easy for the first mile or two after starting.

GSteg

iTrader: (15)

My 2GS does this, but it doesn't bother me. After a mile or so, its back to normal again.

On the other hand, our 2005 Odyssey doesn't do it.

ABC

Same here. Every morning, i'm usually cruising at 80 mph at 3k revs until it shifts after a min or so on the highway

RXSF

Yes it is very annoying, and it is made much worse when the car you are driving doesnt freewheel. My C class feels like its braking right when I release the gas pedal but on cold starts the problem is exacerbated.

However, it can be good since many times I can judge distance without braking but mpg suffers