Having an issue with my speedometer on an LS3 E67 with a 6L90 T43 trans.
-Engine is a GM performance 525hp with the stand alone hot rod kit that utilizes an E67 computer (809-19354332)
-Trans uses an aftermarket wiring harness to tie the transmission to the bulkhead connector. (Zero gravity - they have been little to no help)
When I have the ECM trans type set to Auto as I believe it should be for using a 6L90 transmission I don't get any speedo reference when logging Data in VCM Scanner. (it's an offroad truck, I don't actually have/need a speedometer on it besides GPS). However I believe the ECM/TCM need to know the speed of the vehicle for the trans to shift correctly.
If I set the ECM trans type to Manual, I get a speed for SAE speed in VCM Scanner, but the note in the HP tuners program of "DO NOT" set to manual when using an auto trans has me hesitant to go drive it like this and generated some questions:
1) does changing ECM trans type to Manual make the ECM totally cut off from the TCM? as in no torque mgt, or serial communication
2) If going to Manual on the trans type gives me a speed reference where the heck is it coming from assuming that the ECM isn't looking for an auto trans with serial communication any more?
3) Safe to drive it with Manual in there and use an auto trans with TCM?
4) Is having it set to Manual giving me the signal I am really interested in for the system to work together (shift points, trans seeing speed, etc). Maybe I need to have it set to Auto and I should be looking at how to bring that signal to the ECM through different pins another way?
Trans shifts beautiful when I have the tune set to Manual instead of Auto. I have a speed readout, and I no longer feel the need to chase some of the little shifting issues I was having because they no longer exist! I still don't understand how setting the Engine tune to Manual instead of Auto would make my trans shift correctly besides that it now sees the speed reference? any help understanding would be much appreciated
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