Electronic tranny control compatability?

[Jim Butler]

    Dan,

    Purusing

    http://www.gmpowertrain.com/transmissions/4t65_main.htm

which is for the 4T65E but which I believe's similar to the 4T60E, it's
stated that:


    - Shifts are controlled by two soleniods

    - "Force motor control" to control line pressure for shift feel, aka
    the "pressure control soleniod"

    - PWM soleniod control for TCC control

which, generally, is the same as the 4L60E, as I understand it.  However...

    From my 1995 4L60E reference, "1995 S/T Truck Driveability, Emissions
and Electrical Diagnosis Manual", November 1994, there's other ancillary I/O
functions that may or may not be the same and may or may not need to be
supported.  For instance, my 4L60E has

    - Transmission range pressure switch assembly: A set of diaphragm
switches that are actuated by pressures internal to the transmission which
the ECU uses to sense the position of the manual valve (def'n below).

    - 1-2 shift solenoid

    - 2-3 shift solenoid

    - 3-2 (downshift) control soleniod

    - TCC clutch solenoid

    - TCC PWM solenoid

    - vehicle speed sensor aka transmission output shaft speed sensor

    - transmission fluid temperature

    - pressure control solenoid, i.e., for line pressure control

    The manual on pg. 10A-14 also speaks of an ECU scan tool parameter
called "TCC Slip Speed", which "is the difference between transmission input
speed and engine speed".  This suggests that the transmission input speed is
measured somehow as well, independently of the engine RPM, but I haven't
determined if this is indeed the case and, if so, how it's implemented.
Checking the Wiring Diagram for all ECU supported in this book shows no such
sensor or wiring to the computer (pg. 10A-19 and 10B-18).

    Note that there's no transmission fluid pressure sensor.  Thus, I assume
that there's a built-in, known relationship between the PWM setting of the
pressure control solenoid and the resulting line pressure.  Clearly this may
be differently implemented in the two transmissions.  I'm aware the some
ECUs have a transmission pressure map, and perhaps you could modify the
existing ECU's map if necessary to accommodate any difference in the
transmissions.  I can provide an example map for those who are interested.

    The gear ratios of the two are very similar, so I believe that the
existing shift selection calibration would work fine for the 4L60E.
However, I've gotten a lot of satisfaction by modifying my ECU's shift
tables so that the shifts are occur later than GM's design, and you may wish
to do the same.


    Jim

--
Jim Butler


def'ns:

Manual valve:  The valve which is physically linked to the shift selector
mechanism which controls the principal functioning mode of the transmission,
e.g., PRND321; I'm not sure if other years' 4L60Es have similar manual value
control or not.  For my 1995, the pressures in the transmission are
controlled by the manual valve to initiate such features as
overdrive-disable, e.g., D21 only; the ECU senses these pressures using the
diaphragm switch mentioned in the above.


> I'm running under the assumption (dangerous I know) that the transverse
> fwd 4T60-E is basically the same guts as the rwd 4L60-E.  Does anyone
> know if the communications for controlling these are the same?
>
> I'm researching possibly using a fwd engine in a swap into a rwd
> application.  The stock PCM controls the 4T60-E it came with.  I'd like
> to be able to use a 4L60-E (rather than a TH700 or 4L60).  Would the
> fwd PCM happen to work with fine with the 4L60-E as well (other than
> calibration differences for the different gear ratios and shift points)?
>


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