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Re: [Shop-talk] An off shoot of the Toyota debacle.....

To: shop-talk <>
Subject: Re: [Shop-talk] An off shoot of the Toyota debacle.....
From: Nolan <>
Date: Fri, 05 Feb 2010 14:48:19 -0500
Arvid Jedlicka wrote:
> Tim,
> Thanks. We agree on how it works with just an input pump and various 
> scenarios of the engine running, not running, in a gear, not in a 
> gear, etc. But the original statement from John ...
> implies that there was only a pump on the output side - otherwise 
> there would not have been a qualifier about "both input and output" 
> ... which is why I was asking how that particular scenario worked.
> Your thoughts?
It's part of a major misunderstanding of how torque converters and 
automatic transmissions work.  To start with, not a single automatic 
transmission made has an input shaft.  Not a single automatic 
transmission made has a hydraulic pump driven from a non-existant input 
shaft.  They have torque converters.  The hydraulic pumps are driven by 
the outer casing of the torque converter.  This is directly bolted to 
the engine crankshaft, and slotted into the hydraulic pump.  If the 
engine is turning, the hydraulic pump is turning.  This hydraulic pump 
cannot, and does not, turn the engine when the engine is turned off.  
The hydraulic pump is absolutely incapable of doing this.
Power is transferred to the transmission via the output shaft of the 
torque converter.  This is hydraulically driven by the spinning blades 
of the engine connected casing pushing against the blades of the output 
shaft.  This system is very directional, as the engine turns one way 
only.  It is all but incapable of producing any appreciable force in the 
other direction.  That is why it cannot turn the engine over.
Lock up torque converters are capable of keeping the engine turning over 
if the torque converter stays locked.  I know of none that are designed 
to stay locked when the power to the engine is turned off.
Some automatic transmissions are designed intentionally or incidentally 
to be able to be towed.  This is by some method of providing lubrication 
to the moving parts, usually a seperate lubrication pump on the output 
shaft of the transmission (or transaxle).  This setup does not power up 
the transmission, or produce hydraulic pressure in the actuation system, 
that is a function of the engine driven hydraulic pump.  It simply keeps 
lubrication flowing around the parts that rotate when the car is being 
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