C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Shift light

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Old May 19, 2012 | 05:54 AM
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From: Lenoir City TN
Default Shift light

I know this should be posted in the tuning section but there doesn't seem to be much activity there. Where in the XDF is can you adjust when or how the dash shift light is activated? I'm using the 8D XDF on a 91 OBD!

Thanks

CS
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Old May 19, 2012 | 01:22 PM
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The shift lights that I have used have a pill or dial to adjust the rpm that the light flashes. The light gets the rpm signal from the distributor or ignition box controller. I haven't heard of a controller signaling a shiftlight to go on but I might be wrong.
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Old May 19, 2012 | 06:09 PM
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There is an actual "shift" light on the dash to the right of my digital speedometer that comes on when the car reaches around 2500 rpms. I can't find it in the program to change it or shut it off. I thought there would be a "flag" or something that I could change in the program to alter it.
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Old May 20, 2012 | 03:08 AM
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Without looking at the code... (this is for my '86 BUA firmware, but yours will be similar):

I don't think there is a table for this. It depends on what gear you are in and the Load Value. I'm pretty sure it's a calculation that the firmware does.

Well I didn't want to take the time to look at the code, but I did anyway and found four tables that determine when the shift light goes on and off:

Manual - 1st gear downshift / Auto - non 4th gear unlock
Manual - 1st gear upshift / Auto - non 4th gear lock
Manual - non 1st gear downshift / Auto - 4th gear unlock
Manual - non 1st gear upshift / Auto - 4th gear lock

(Now I know why my TCC kicks in at the same time the shift light comes on) I don't know the table names because I'm looking at a disassembly and my table addresses wouldn't work with your firmware either.

I know there has to be some other criteria because I remember that the shift light will also come on at "red line" (and off at a corresponding value).
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Old May 20, 2012 | 06:49 AM
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Thanks Cliff, I remember seeing those. I take a look and see what I can come up with.
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