[Gmecm] Re: Gmecm Digest, Vol 13, Issue 8

[William Lucke]

Very intersting...

 From the '89 Technician's Guide for 4L60 (700-R4) (and all other 
available resources including an '83 "Principles of Operation" manual) 
the convertor and cooler hydraulic circuits are decoupled from every 
other hydraulic circuit in the trans. This means that the TCC fluid flow 
always behaves the same way no matter what gear the transmission's in.
The TCC is controlled by two hydraulic lines... apply/return and 
release. When released, pressure goes to the release side of the TCC 
piston and through some mechanism not readily obvious from the manual 
flows back through the apply/return line and then goes to the cooler.
When applied, the fluid goes to the apply side of the piston and only 
leakage past the piston flows back through the return line. From there 
the leakage is exhausted into the pan. When applied, there is a parallel 
connection made through an orifice to the cooler lines.

What this information shows is that the orifice passes more fluid than 
the piston when the clutch is released.

When unlocked in 4th gear, the engine RPM is low, putting the convertor 
in high slip operation. Extended operation in this state just develops 
too much heat for the cooler to deal with.
We know from watching a transmission temperature gauge during extended 
cruise with the TCC applied that the trans fluid gets down to the same 
temp as engine coolant on the stock trans cooler in a '79 Suburban.



Will



> From: Andrew Gibson <andrewsharyn at yahoo.com>
> Subject: [Gmecm] Geting rid of electronic transmission.
> 
> Here's some info to put to rest the debate as to 4l60e/700r4 cooler flow. I flushed one today and my flush machine has a gpm flow guage on it, so I took advantage of it. I know some of you are going to say you've seen otherwise. So have I, but the numbers were either a little higher or a little lower. But not radically different.
>    
>   At Idle
>   Park .8gpm
>   Reverse 1.2gpm
>   Neutral .8gpm
>   OD-1st .8gpm
>    
>   2000 rpm wheels spinning
>   Reverse 1.2gpm
>   1st .8gpm
>   2nd .8gpm
>   3rd no tcc .8gpm
>   3rd tcc 1.3gpm
>   4th no tcc .8gpm
>   4th tcc 1.3gpm
>    
>   Obviously having the tcc engages increases cooler flow, but the flow never stops. Why the increase? The tcc piston is applied with fluid pressure. Most trans clutch pistons have a vent hole that leaks. Leakage from the tcc means more fluid being put in the converter so more has to return to the trans... through the cooler. Point blank: the cooler always flows no matter what. It just flows more when the tcc is engaged. So it looks like all of us were at least somewhat right concerning the cooler flow.