mpesik

Hello. I was wondering does putting an auto tranny in neutral at a light or while coasting to a stop, have any cooling effect on the transmission oil at all? Mike. Thanks for your reply.

jpitman2

mY OWNERS MANUAL RECOMMENDS IT..not to be stationery in gear for long periods anyway. Neutral will allow the torque converter output shaft to spin freely, which will reduce heat generation in the oil, and keep it pumping around the system. I have seen an 85 auto with an extra tranny cooler in front of radiator, in series with normal cooler - told it was a factory set up(looked it too), so they obviously though it needed some extra help.
jp 83 Euro S AT 48k

Nicole

At a traffic light, it is pointless because of the much longer time it takes you to put the car back in gear than with a manual transmission. Stop and go is also not practical.

But if you know you are going to be stopped for a few minutes (e.g. at a railroad crossing or a drive-through while waiting for your order), then it only makes sense to put it into neutral or park. But in those cases it makes even more sense to turn the engine off and restart when things get moving again.

There is no point in letting the beast idle, if you are not going to move for a while. It wastes fuel, creates unnecessary emissions, makes noise, and when the enginie is cold wears the engine faster because it takes longer to warm up at idle.

In short: Use common sense!

Doug Hillary

Hi,
John and Nicole's call are both correct. It is in the Driver's Manual - even for the S4!!

In long immobile traffic jams on a hot day it makes a lot of sense as the heat in ATF builds up quite quickly. We all know that excessive heat is a killer for the seals etc - andd for the ATF

In monitoring my engine compartment temperatures these were recorded from the Transmission cooler;

Order = highest, lowest, average, median - in Celcius

In = 83, 43, 60, 61

Out = 77, 31, 50, 51

Note that the heat loss is about 10-15C across the cooler. The median loss being 10C

My car is rarely ever operated in heavy and slow city traffic and I use a fully synthetic ATF (Castrol's Transmax Z) which greatly assists in dissipating heat from the transmission

Conventional ATF's (which are semi-synthetic) will tolerate quite high temperatures. Synthetic ATF's do the job better and some tend to remove up to 20C more than a conventional ATF

Regards
Doug

Jim bailey - 928 International

Thanks again Doug ....facts ,figures, data , good sound advice PLUS he even reads the owners/operators manual ...........

mpesik

I can not find that info anywhere in the owners manual!! Thanks for replying.

Randy V

I think it does.

Calibre26

What is the consensus on letting the engine idle (warm up after a cold start)? How much time is too much before you plan to drive?

I should mention that I am a Canadian shark owner - We often find ourselves at the lower ends of the thermometer (sometimes even in the summer time).

Thanks,

J

Leon Speed

Phew. Glad we got that settled

WallyP

Standard manufacturer's recommendation is to drive gently away as soon as the engine will run smoothly.

tv

I often start mine leaning in from outside and always let mine idle for a while before starting off, cause that's how I roll.


Unless you are some kind of environmental nervous nelly, why not let it get up to proper operating temp before running, get the tranny oil circulating, (supposed to measure it warm with engine idling), get the idle back to normal (see the thread about driving in ice in Netherlands at high idle).

While its idling, I like to walk around and check everything and listen to the exhaust, then I get in, buckle up, at night turn the **** and watch the frog eyes pop up and then go. But like others I don't use it in traffic.

I do have one of those little front aux. tran oil coolers, chock up another one for the euro. But I would not throw it into neutral while cruising to a stop because 1) I like the burble I get 2) the euro engine brain cuts off the fuel in those situations, 3) extra wear on tran gear.

Mark SF

"Unless you are some kind of environmental nervous nelly, why not let it get up to proper operating temp before running, get the tranny oil circulating, (supposed to measure it warm with engine idling), get the idle back to normal (see the thread about driving in ice in Netherlands at high idle)."

Because it causes more wear, not less. By driving gently as soon as the engine runs smoothly, the engine warms up more quickly. That means it spends less time in the critical state for wear - cold engine, cold oil, bad clearances, possible over-fueling with consequent washing of oil from the bores.

Speedtoys

At a traffic light, it is pointless because of the much longer time it takes you to put the car back in gear than with a manual transmission.
---
How do you figure that?

tv

I think you have to throw out the human time factor here because the engine sees thing in RPM's. Driving may or may not warm it faster but if it does it does under some load. That load causes stresses and friction.

Idling at 1000 rpm's for 7 minutes vs. driving at 3500 RPM's for 2 minutes = both engines operating for 7000 total rpm's


Same RPM's seen by the engine, longer time seen by the human, while idling no load on engine, oil comes up to temp, coolant comes up, metals expand. Happy engine. Driving right away puts load on engine that is not up to temp. Same amount of fuel used as far as the washing but I have never had any smell in the oil and change it often enough.

Engines live by RPM's not the clock (or the odometer) I'll stick with idling. This might be a cross-drilled rotors type of discussion.

Speedtoys

IMHO, overall warmup, once started, happens faster in the first mile than minutes of idling.

NOte..that at 35 below, you might idle for a minute first...but thats an extreme case.


And..that first mile is not bwwahhh driving, just..driving.