Hypermiling in a 2011 Elantra? Could some of the techniques hurt the transmission?

[regor]

I am fan of hypermiling to save fuel. One of the steps is on downhill stretches or coasting up to a light that I know will be red, I’ll shift the vehicle from drive to neutral (and back to drive when I’m done with the downhill coasting). If I’m coasting up to a light that I know will be red for long, I will turn off the engine. I do this with my Honda Civic and Chevy Silverado. However, with my 2011 Elantra, there is a notice in the manual (5-17) to “Always come to a complete stop before shifting into D”. I’m aware that Hyundai has a new transmission in this vehicle.

So the question is: Can I still shift the Elantra into neutral from drive while the vehicle is moving and shift it back into drive from neutral while the vehicle is moving without damaging the transmission.

Thanks!

[ItsNotAboutTheMoney]

Neutral (NICE-ON) coasting should be ok, but it's not flat towable so turning the engine off can harm the transmission.

The general rule people apply to NICE-ON is that if the car shifts* smoothly between neutral and drive it won't harm the transmission.

Best just to leave it in neutral.

[phoebeisis]

My primitive 1998 4L60E with 5.7 feels exactly the same in D(lifted off gas) as N- glide times/distances/speeds exactly the same.It has ZERO engine braking at most speeds in top gear.
No point in putting some vehicles in N.

[MaxxMPG]

As mentioned above, the Elantra is not flat towable, so "if the wheels are spinning, keep the engine spinning". Cutting the engine while the car is rolling will damage the transaxle. Shifting to neutral while driving is ok.

The warning in the manual about "stopping before shifting to drive" is there to caution drivers not to back up and then shift to drive while the car is still rolling backwards. On a few occasions, I've ridden in cars where the driver would back from the driveway or parking spot and just shift to drive while the car was rolling backward at a brisk walking pace. Although the torque converter can slip enough to keep the engine from stalling during this shift, it stresses the internal gearset beyond its design limits and it leads to accelerated wear on the clutch packs. It can also cause internal parts to break if the accelerator is applied during the shift. If the Elantra transaxle has the same clutch application schedule as that of the Sonata, the shift from R to D causes the release of the "3-5-R" clutch and the apply of the "underdrive" clutch while the "low/reverse" clutch remains applied. In this case, the clutch that bears the strain of a botched R-to-D shift is the underdrive clutch, which is applied in 1st through 4th gears. Since the low-reverse clutch locks the same component (output carrier) as the overrun sprag clutch (that allows the car to coast unless downshifted to a lower gear), stressing the transaxle enough to cause slippage of that low-reverse clutch can fracture the race of that sprag clutch. When that happens. The car only moves in reverse, and can go forward only if shifted manually to first.

You can key-off for long red lights, railroad crossings, or other extended stops, but do so after the car is stopped. Leave the car in N so it will restart when you're ready to drive on. After restart, bump the lever to D and it's ready to go.