"Manually shfting" an auto tranny...

[David A. Cooley]

At 07:48 PM 5/31/99 -0400, you wrote:
>Hi folks, I'm pretty ignorant when it comes to trannies, and was wondering if 
>someone with a bit of knowledge of modern auto trannies might help me out. Am 
>I correct in assuming that most newer auto trans (maybe even old ones too?) 
>use a single solenoid to control the flow of oil, which determines the 
>shifting of the tranny? If so, is it possible to control the shift points of 
>the tranny, assuming that you eliminate the stock programming in the tranny 
>ECU? I was just thinking that one could hook up a switch to that shifting 
>solenoid and shift "manually"...or maybe it can still be done, but another 
>way? 

On a 4 speed auto trans (GM is where I get my experience), there are 2
solenoids...  The trans will shift itself if the engine is revved high
enough without input from the solenoids by governor pressure, and
re-programming can be done if you know where the tables are in the chip...
The modern GM 4spd Auto's have the 2 shift solenoids, a torque converter
clutch lock-up solenoid and a line pressure modulator.  You can vary the
firmness of the shifts along with where the shifts occur.
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           David Cooley N5XMT           Internet: N5XMT at bellsouth.net
     Packet: N5XMT at KQ4LO.#INT.NC.USA.NA   T.A.P.R. Member #7068
   Sponges grow in the ocean... Wonder how deep it would be if they didn't?!
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