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Old 05-13-2014, 07:24 AM   #27 (permalink)
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Originally Posted by Old Mechanic View Post
I've coasted in neutral (only engine running) in autos for probably a decade, several different cars, regular autos, CVTs, and 23+k in the fiesta powershift.

Engine off coasting in neutral?

You will never see me do that in any auto transmission. In almost ever auto tranny made there are two flanges on the back of the torque converter that engage the primary pump of the transmission. When you turn the engine off, the torque converter stops rotating, since it is bolted to the crankshaft, so you have no primary pump and no pressure for gear actuation or lubrication, and neutral needs activation to unclamp all of the bands that engage the planetary gearsets.

Would you run your engine without oil pressure intentionally?

You will never see me coasting in neutral, with the engine off, in any auto transmission, until the manufacturer guarantees me that they will replace the transmission if it fails.

They won't.

Engine on only in autos. Engine off is risking a several thousand dollar repair, in many cases more than the car is worth.

Manuals are fine with engine off coasting.

Have to agree. Was in the towing business back in antiquity. Lots of rules about about which automatics could be towed drive wheels on the ground. Some X number of mile at <Y speed others not at all. These assumed the transmission was in good condition. Best bet was flatbed, drop the drive shaft or dolly.
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