Alternate starting methods

[GTRS Fiero]

On a manual transmission vehicle, you could put the transmission in, say, 1st gear, push in the clutch, turn the ignition to "RUN", have someone push the car about 10 MPH, and pop the clutch to start the engine.

With an automatic, we used to do much the same, except just clange the gear from N to D, while going 40 MPH or more.  Is this still do-able?  Bad idea?

[Fierofool]

Many automatics of today can't be push-started.  They are designed to be towed and the driveline doesn't push the fluid. 

Some of the older transmissions, like the TH125c in the Fiero have warnings on speed and distance the vehicle can be towed with the drive wheels on the ground.  Just guessing, but maybe it's because the driveline is pushing the fluid through the valve body, pump, and torque converter in a reverse direction.  If that's the case, it seems like it would be possible to pull it into a gear and would result in the transmission turning the engine over. 

[Raydar]

Many automatics of today can't be push-started.  They are designed to be towed and the driveline doesn't push the fluid. 

Some of the older transmissions, like the TH125c in the Fiero have warnings on speed and distance the vehicle can be towed with the drive wheels on the ground.  Just guessing, but maybe it's because the driveline is pushing the fluid through the valve body, pump, and torque converter in a reverse direction. 
...

What I've heard about flat-towing a Fiero (or most any other modern) automatic, is that the internals will not be lubricated, because the pump is not turning, and pumping fluid. (The pump is geared to the input shaft, along with the torque converter.)

[Fierofool]

Pat and I talked about starting the engine and letting it idle for the 3.5 hour drive back home.  Do you think that would prevent damage to an automatic? 

[GTRS Fiero]

I think so.

[GTRS Fiero]

Did you do it?  I had thought it was decided that the transmission was bad, anyway.

[Fierofool]

Yeah, we figured the trans was shot, so I just tied down the steering wheel, left the ignition in the OFF position and the shifter in Neutral. 

[GTRS Fiero]

Supposedly, some vehicles can be put in free-wheet mode, for being towed flat.

I have heard that the lock on the wheel can break, when being towed flat with the wheel locked, but tying it down should help.

[Wreck It Ralph]

As an transmission mechanic I have never heard of any automatic transmission that you can jump start the vehicle with a rolling start. It’s a matter of design. The engine turns the torque converter which turns the pump. The fluid pressure the engages a gear by means of a band, servo, piston, or lip seal(im sure I missed one). In drive with the engine off you will notice how you can’t really push an automatic car and that’s because it’s particularly engaged. So it’s not exactly in 1st gear like you’d think, even if you drop it to 1st or low. You could cause serious damage to a transmission attempting a push start.

As for towing. The issue is lubrication. Yes if you flat tow or tow on the drive wheels of most automatic vehicles then you will burn up the trans. Transmissions require stupid amounts of lubrication. You have to think about a hydraulic pump that also moves a car and that is an automatic transmission. If you had X-ray vision and looked at one while off you’d notice that it’s like 1/2-3/4 full of fluid. But it’s not moving and more importantly not cooling. Thus why you’d kill it mile by mile towing. So yes if the pump was working and you had fluid in it then a flat or drive wheels down tow would work with it in neutral and engine at idle.

The reason some cars can be flat towed (besides being a manual which relies on splash lubrication instead of a pump) is simply design. In neutral they do not partially engage and most likely they are a sealed or 90% full unit. This is great for towing but it has its dark side. They are prone to major failures due to low pressure or fluid. The transmission relies solely on pressure to engage the gears. Thus if it gets low or the pump wears just a bit and smoke the transmission. So there is pluses and minuses to this style.

To avoid all these problems... you guessed it, go manual.

I hope some of my incoherent ramblings helps some to understand the how and why.

[TopNotch]

My first wife had a 56 Chevy with a 2-speed slush-o-matic transmission in it. I actually roll started that car once. Going down hill, I threw it into "1" from neutral, and it started.

[GTRS Fiero]

We had a '77 Dodge van with a custom 440V8 that we did in fact start by getting it up to 40 MPH, then shifting from neutral to drive.  On other occasions, it was under its own power at 60 MPH, placed in neutral, the key changed, turned to run, and the transmission moved back to drive.  The engine refired, and we continued driving.  This sort of thing was common.

We had a '78 GMC pickup that had a bad starter.  It was common to park the truck at the top of a hill, and start the truck by letting the truck roll down the hill, then shifting to drive.  That happened for 2 weeks, until we got the replacement starter.  That truck was odd, though.  It had L1 & L2 marked on the gear indicator.

[GTRS Fiero]

The '56 was before my time.  My dad had a '57 Chevy.  I barely remember that car, but my aunt drove the car to Chicago in 2nd gear.  I think that Chevy had a manual transmission.  Whatever it was, she burned up the transmission.

[Raydar]

As an transmission mechanic I have never heard of any automatic transmission that you can jump start the vehicle with a rolling start. It’s a matter of design.
...

My parents had a '58 Dodge with a peck-o-matic (pushbutton) automatic, and an ancient POS Hemi that didn't ever want to start. They had to push start that thing several times. As I recall, it actually worked.

(And yeah... I'm showing my age.)

[GTRS Fiero]

So, not anymore?

[GTRS Fiero]

As I think about thix, I flat towed my brother's '92 Dakota a total of about 300 miles.  I flat towed a '95 Blazer about 80 miles.  I flat towed a Ranger some 25 miles.  And there were others.  All those were automatics.  That's why it surprised my that the Fiero could not be flat towed.  The explanation I was given, is that the Fiero has something different about the transmission.  Of course, the Fiero essentially has a FWD transmission.  Those other vehicles were all either RWD or FWD.  Could that be the difference?