Trailblazers and Envoys Offroad

Transmission Technical Documents – 4L60e

Through my research I’ve run across a few very helpful documents regarding the trailblazer transmission (the 4L60e).  I’ve amassed them here.

Electronic Controls Document:

Details of the internal wiring, pin-outs, and other electronic details.
electronic controls

Hydraulic Schematic:

(Left is the key document, right is the actual schematic file)
Details of the internal hydraulic routing and their functions.
schematic key hydraulic schematic

Transmission Overhaul Detail:

Factory detail of a complete transmission overhaul.

Conversion to Manual Shift:

An interesting article detailing how to convert an eletronically controlled 4L60e into a manually-shifted transmission.
manual shifting

  • Howard Wilkinson says:

    Good stuff…………… I have modified my 4L60E with a manual TCC lock up switch for towing, and disabled the PWM valve by installing a spring heavy enough that it cannot modulate the pressure. I pull a tandem trailer, often heavily loaded with a 4.3 powered pickup and 3.07 gears……… by heavy, I mean as much as 10,000 lbs payload. I have put 60K on the pickup since these mods (170K total miles), and of course have to manually shift when pulling………… I’m looking at doing a tranny flush by pulling the pan, and pumping fresh fluid in via the pressure test port, then after putting things back together and filling the pan, pumping a pint or so out the same port to clear the suction line and any dead space. Do you see anything wrong with this procedure?

    September 28, 2013 at 7:39 pm
    • JamesDowning says:

      Howard, we don’t generally suggest pumping fluid into the transmission, especially when the engine is off.

      If you are wanting to perform a flush, we recommend draining the transmission via the pan, keeping the old filter in place, and refilling the fluid with some cheapola trans fluid. Run the vehicle for around 300-500 miles. At this point, drain the fluid from the transmission. If the fluid still seems overly dirty, perform the same step again, running for 3–500 miles. Once the fluid starts draining a little cleaner, replace the filter with a new one, and put some expensive trans fluid in there. We call that a flush.

      October 1, 2013 at 1:32 pm

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