03 6L 4L80E VSS 1/2 GPS Speed

[TurboCamaro]

I have a 6L 4L80E swapped vehicle that was brought in for a speedo calibration as it shifted hard and the speedo wasn't calibrated for the gears and tire size.
The engine, trans, harness and computer all from an '03 4x4. The output of the trans was changed to make it a 2WD and the VSS was moved to the trans tailshaft from the TCase.

I didn't do the initial cal for the swap so don't know all that was changed from stock.

Upon calibrating for the gears and tires the VSS was off by about half (GPS showed 50MPH and VSS showed 27). I thought at first it was thinking it was in lo range on TCase and maybe pin 16 was grounded but this is not the case.

I tried to cheat it by offsetting with the speedo calc now the VSS and GPS match but it is shifting at 2x the mph at TPS in the part throttle shift tables ( 1-2 shifts at 39 when it should shift at 19, 2-3 shifts at 40 when it should shift at 19, what a coincidence these are the same value although different TPS).

Any thoughts?
Attached are calibration as pulled and the current cal with log file.
Thanks
Eldon
23752
23753
23754

[nonnieselman]

I have a 6L 4L80E swapped vehicle that was brought in for a speedo calibration as it shifted hard and the speedo wasn't calibrated for the gears and tire size.
The engine, trans, harness and computer all from an '03 4x4. The output of the trans was changed to make it a 2WD and the VSS was moved to the trans tailshaft from the TCase.

I didn't do the initial cal for the swap so don't know all that was changed from stock.

Upon calibrating for the gears and tires the VSS was off by about half (GPS showed 50MPH and VSS showed 27). I thought at first it was thinking it was in lo range on TCase and maybe pin 16 was grounded but this is not the case.

I tried to cheat it by offsetting with the speedo calc now the VSS and GPS match but it is shifting at 2x the mph at TPS in the part throttle shift tables ( 1-2 shifts at 39 when it should shift at 19, 2-3 shifts at 40 when it should shift at 19, what a coincidence these are the same value although different TPS).

Any thoughts?
Attached are calibration as pulled and the current cal with log file.
Thanks
Eldon
23752
23753
23754

Remove rear VSS and look in the transmission. See if there is a reluctor/tone ring for it to read off of. I had a "built" 4L80E that they must have used a 4x4 rear carrier cause the reluctor was missing and i was picking up the park pawl teeth.

Also double check wiring from ISS/VSS to PCM. Make sure they are in the correct pin location and not mixed up at the transmission.

Might want to start with a factory transmission tune and adjust from there. Worked on a old suburban with a 4.8/4L80E swap and it took forever to get it to shift right. Had to start over from a stock tune, whoever had tuned it before had it so far off it wasnt funny.

[TurboCamaro]

Thank you.
Will check these.

Would anyone have a stock 12582603 Cal I could leverage for this. It is an '03 6.0L w/4L80E

Thanks

[nonnieselman]

Thank you.
Will check these.

Would anyone have a stock 12582603 Cal I could leverage for this. It is an '03 6.0L w/4L80E

Thanks

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