Neutral to drive coast, is it bad for newer auto trans

[mcrews]

Originally Posted by Whoops

My experience, I did this with my wife's van. It cost me $2000, to put a new transmission in. The amount of money you can save, just isn't worth the risk, IMO.

And (of course) your going to tell us the make and model of the Van???????

[mcrews]

Starting in mid-2002, JATCO introduced the RE5R05A:
a rear-wheel drive, 5-speed automatic transmission used in the Infiniti Q45.
Since then, this unit has appeared in Infiniti and Nissan drivetrains.
Infiniti uses it in CX25, FX35, FX45, G35, M35/35x, Q45, and QX56 vehicles.
Nissan uses it in the 350Z, Frontier, Pathfinder, Armada, Titan,and Xterra.

[mcrews]

I can shift in and out of neutral at any time and any speed on the Q45.

[redpoint5]

Originally Posted by Thymeclock

The potential problem comes not with putting the transmission into neutral and coasting, but rather when you re-engage it into drive. If you coast to a stop (or an almost stop, meaning below 10 MPH) there will be no harm incurred.

This is my understanding based on nothing but driving impressions of various vehicles. When I try to drop back into drive on my Dodge Ram, the engine races and the truck rapidly decelerates as it thinks about shifting into a higher gear. Other cars such as the Toyota Camry don't appear to exhibit this behavior.

While I don't have any hard evidence one way or the other, I would say if it feels harsh, it probably is. If not, you are probably fine.

[user removed]

Engine on coasting in an AT equipped car or truck depends on the vehicles ability to reengage the transmission without any trauma. My 08 Altima would reengage easily with almost no perceptible deceleration. It did this by engaging in the highest ratio (CVT) with the torque converter lockup disengaged. Even at 70 MPH the initial engagement would get the RPM to increase from idle (700) to about 13-1500, then after about another second or two the RPM would increase to the same level as it was when you were driving at the same speed. Worked fine up to 80 MPH. I never tried it above that speed.

regards
Mech

[2.Slow]

Originally Posted by UFO

Yes, just engine off. I've been engine-ON coasting with my automatic for a while, and it has the pump on the input shaft.

In any case, it takes practice, but if you can do it smoothly it shouldn't be a problem. I've been doing it everyday for a year or so with my notoriously unreliable O1M VW automatic and it has not developed any issues (yet).

Hi UFO,
I'm newly registered here to ecomodder (long time lurker) and happened to run across your recent post on the coasting in neutral with the VW 01M transmission and wanted to pick your brain on some tips. I have a 2002 VW jetta 2.0 with the 4 speed trans as well. I've had a heck of time just getting the mpg to increase from an average 20-21 to 26-28, which took replacing nearly all known mpg influencing parts and getting the scangauge, but I feel I'm still limited by this darn transmission.

Hence, it was good to see someone with the exact same transmission since I feel that is the major limiting factor on these cars. What sort of tips have you done to overcome this? i.e. what were your optimal speeds/gears. I've found 50-55 is the sweet spot. I've starting coasting in neutral with engine on as long as I'm coming to a stop.

Any help would be greatly appreciated!

[UFO]

I increased my mileage from 37 to 45 partly due to my engine-on coasting, partly due to my slowing down and timing my stops. Given the limitations of the VW O1M, I don't think I am going to be able to make many further improvements with driving technique. It looks like you may have hit the limit of yours as well.

One major goal of mine when driving in traffic is to get up to the overdrive shift points as soon as practical, and stay there. My first overdrive shift point is 30mph indicated, and I can drop 2mph and still stay in OD. The final overdrive shift point is 42mph, and I can drop down 3mph while still staying locked up.

If I anticipate a light is going to change, but I cannot hit it while staying in lockup, I disengage the tranny and coast to the light, hopefully maintaining my momentum as I get to the light. As soon as it changes, I reengage the tranny (NO accelerator!) and wait 2 seconds for the hydraulics to fill, then re-apply the accelerator to get back to my shift point.

If the light is not going to change, I leave the tranny in gear and engine brake to the light before shifting into neutral to wait for the light change.

If the O1M decides to break, I will probably do a 5 speed manual conversion. For some reason, the VW automatics get worse mileage than most other manufacturers' automatics.

[2.Slow]

Thanks for the help. You make good points for getting to the highest overdrive as quickly as possible. Since getting the scangauge, I've noticed there is a tremendous jump in FE when making it into the 3rd and 4th gear.

Do you tend to speed up to these faster than the preferred 1.5-2gph since the gain in mpg is so substantial?

[sheepdog 44]

I've done this in my AT Saab. It will take your transmission from potato salad to jello. On which ever speed you re-engage your transmission there will be a dull spot at that speed that may or may not go away eventually. That'll make your transmission less responsive and require more finessing and more accelerator to get up to speed. You won't shift as readily or as fast and it'll shift at a slightly higher speed and rev. (And i'm talking doing this 10 or less times in total)

Maybe some rare cars are designed to do this without wear, but i think the categorical recommendation should be do not do it!

Do:

Sell your car.
Buy a more fuel efficient model with a manual.
Stop wasting your time trying to coax more from a cast iron tub with wheels as is my case.
Do it sooner and you'll save more gas.

[UFO]

Originally Posted by sheepdog 44

I've done this in my AT Saab. It will take your transmission from potato salad to jello. On which ever speed you re-engage your transmission there will be a dull spot at that speed that may or may not go away eventually. That'll make your transmission less responsive and require more finessing and more accelerator to get up to speed. You won't shift as readily or as fast and it'll shift at a slightly higher speed and rev. (And i'm talking doing this 10 or less times in total)

Maybe some rare cars are designed to do this without wear, but i think the categorical recommendation should be do not do it!

Do:

Sell your car.
Buy a more fuel efficient model with a manual.
Stop wasting your time trying to coax more from a cast iron tub with wheels as is my case.
Do it sooner and you'll save more gas.

Hasn't happened yet; I've been coasting every day for over a year now. As far as "wasting your time trying to coax more from a cast iron tub with wheels", that runs contrary to the spirit of this site, where we do the best we can with what we have. It might be cheaper for you to switch cars, but I assure that is not the case for most drivers, especially for me as fuel is extremely cheap as it is made from free recycled vegetable oil. If I were to get 10mpg better economy with a manual transmission, at $1 per gallon of fuel, and a straight vehicle trade, it would still take more than 3 years to pay the extra registration fees and taxes associated with buying a different car.

Not to mention the person who ends up with my old car would not get the mileage I did.