Is it possible to push start a car with automatic transmission?
Use case: Let's say the battery is dead or you have a bad starter. I know this can be done on manual cars by putting the car in to gear after the car starts moving.
Can you do the same with an automatic transmission?
Does the automatic transmission type matter? (traditional torque converter, CVT, DCT, etc.)
Automatic transmissions originally had a feature that allowed push starting, a rear pump in addition to the front pump. If the car was rolling the rear pump would provide pressure even if the engine was not running. Some speed was required 15 to as much 30mph recommended for some makes to transmit enough torque through the torque converter to turn the engine for starting. All automatic cars through 1958 and some into the mid 1960s were push startable, some examples are GM's hydramatic through 1958, Chevrolet's powerglide through 1966, Fordomatic/Cruseomatic through 1963 and some Fords through early 1968, Chrysler's Torqueflite through 1965. Reference "how to push and tow automatic drive cars" inside back cover of MOTOR AUTO REPAIR MANUAL.
From experience, my old Mazda 323-C Auto could be bump started at a speed of around 34mph (which is far too fast to push!). This was a traditional type auto box so I don't know how it would differ for something with a CVT / DSG gearbox.
I used to carry jump leads in the boot of this car as the most effective way to starting any car but certainly an automatic with a flat battery is to jump the car using another car or a jumper pack.
If your started motor is dead, check that the exciter cable is alright and without breaks as this can stop the starter spinning over. Is this a real world problem? If so, what is the make and model of the vehicle and what are the symptoms?
I believe you can do it with a traditional torque converter. I've done it. It's not smart.
Push by your buddy, no. Push with another vehicle, yes - but as the other Steve M suggests you'll need the high side of 25-35mph to maybe make this happen.
Without the tranny fluid pump driven, you won't get TC proper fill, BUT there's usually enough residual fluid left in the TC to attempt this unwise stunt. It;s the difference between a really good transmission fluid service and the ones we all actually did... How many of us oldtimers removed the shield (back when you could) and rotated the TC, pulled the plug, and drained the converter? No flame here; I'm as guilty as any.
On edit: I should qualify that as I'm talking old-school. C5 or 727 era, early totally hydraulic systems, where you will always have some reverse power path back to the TC. Modern TCM solenoid valve systems I doubt it, and I simply don't even know. I think I remember working on something that was stuck in an "emergency tow mode" that purposely uncoupled the power flow path to prevent damage (likely dry pump burnout) during flat towing.
I believe that the possibility to push-start a modern car with a completely dead battery is a myth. I tried it once with a manual transmission car along with several workmates that helped to push the car. Even despite achieving significant speed, no gear would start the car. I even tried to turn the key at the same time I released the clutch pedal, just in case the car was designed not to be push started!
The problem is that typically, if the battery has no charge, it is close to zero volts. How do you excite the alternator's coils if the battery has close to zero volts? The alternator in modern cars is electrically excited and has no permanent magnets.
I ended up fetching my jumper cords, which helped to start the car.
If push-starting is practically impossible with manual cars, no amount of pushing will start an automatic transmission car. Of course, all of this applies only if the battery is completely out of charge. If there is some charge left, but not just enough to start the engine, the charge may be enough to excite the alternator's coils and therefore start the engine.
