EOC with Toyota automatic
 

I have a 1996 Toyota Previa with supercharged engine and 4-speed automatic. Unfortunately I wasn't able to get this with a manual transmission. Recently to save fuel when approaching a stop sign or traffic light that I know I'll be stopped at for more than 30 seconds I've been shifting into neutral and shutting the engine down while approaching the stop at anywhere from 25-55 mph. I understand shifting an automatic from neutral to drive while the vehicle is rolling could cause transmission damage so I only do this when I know I'm going to be stopping. My question is am I doing damage to the transmission by coasting in neutral with the engine off. It sounds like some makes and models of transmissions are more prone to damage from this type of driving than others so I'd like to know about the transmission in the Toyota Previa in particular. It seems to me like since I am coasting for relatively short distances with the engine off the transmission is not likely to overheat from lack of ATF circulation with the engine off.

is the supercharger stock? thats pretty cool to have. It doesn't help fe but it helps performance.

Do you know if you Previa can be flat towed? If it can then you know the tranny is designed to be moved and lubricated with the engine off hence coasting in neutral and engine off wouldnt cause damage

Yes the previas had an option of a S/C.

I don't know if it can be flat towed. toyota automatics are pretty gutsy but the cost of a new transmission will far far outweigh the cost of the 20 seconds of engine off time. you won't do any damage to a rwd toyota trans going from N to D. if you're worried about it, give the engine a little gas to match revs before shifting back to D.

it's just like clutch wear (it IS clutch wear on the packs in the tranny) if your at highway speed with a low geared tranny and the trans has to bring it from idle to 4k, then yes you might do some extra wear on it but at low-near-traffic-signal speeds you won't hurt it.

US spec Previas were available with superchargers from 1994 to 1997. The S/C version actually had a higher EPA MPG rating than the naturally aspirated version. This is because the higher torque output of the S/C engine let them use taller gearing so the engine runs at lower RPM.

I'll have to dig out the operating manual to see if Toyota approves flat towing. I vaguely remember it saying something like up to 50 miles below 50 mph. For now I'll just put it in N and coast with the engine idling. If nothing else that will save wear on the starter. It sure was a nice sound, coasting to a stop with the engine off and sitting there silently. Reminded me of the times I've driven electric cars.

I found the owner's manual for my Previa. It is a RWD model and regarding towing the manual says "Never tow a vehicle from the front with the rear wheels on the ground, as this may cause serious damage to the transmission".

However it also has a section on emergency towing where it says "If towing service is not available in an emergency, your vehicle may be temporarily towed by a cable secured to the emergency towing eyelet under t he front of the vehicle. A driver must be in the vehicle to steer it and operate the brakes. Towing in this manner may be done only on hard-surfaced roads for a short distance and at low speeds. Also, the wheels, axles, drive train, steering and brakes must all be in good condition. If the engine is not running, the power assist for the brakes and steering will not work so steering and braking will be much harder than usual".

So I'm a bit confused if EOC from a highway exit to the stop sign at the end of the exit is harming the transmission. On the one hand they say to never tow with the rear wheels rolling but then say it can be done for a short distance at low speeds. I wonder how short a distance they mean, 25 miles to a service station at the minimum highway speed limit or just around a parking lot at walking speed. If the issue is the transmission heating up from lack of oil circulation it doesn't seem like a one minute coast down from 55 mph would generate enough heat to do damage.

By emergency towing, they mean you've stalled out in the middle of traffic and you need to get off the road before you get run over by a semi. walking speed and very short distance. The kind of towing that is illegal to do in most states except in emergencies.

now really, the cost of gas to run the engine in neutral for that, as you say, short distance is not going to kill you and will certainly pale in comparison to the price of a new transmission not to mention installation...on the off chance you blow it.

When you have the engine off, does it still rack up the miles? I know newer cars with digital odometers don't, but if yours doesn't record the mileage with the engine shut off then you wont see an increase in MPG.

Most speedometers will work when you have the key in the 'on' position.
Turn off engine then turn the key back to the running position.