Hypothetical question:

2001 LQ4 4L80e GMC

Tables / Values (D0913, D0918, D0928, D0914, D0919, D0933) are manipulated thusly:

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(These apply when the column shifter is in manual low position)


[D0913] Manual Hold Gear 1st 1->2

Maximum speed before the PCM will force an upshift to 2nd if the gear lever is being held in 1st

Set to out of range

[D0918] Manual Hold Gear, 1st, 2->3

Maximum speed before the PCM will force an upshift to 3rd if the gear lever is being held in 1st

Set to out of range

[D0928] Manual Downshift 1st 2->1

When slower than this speed the vehicle can be put into 1st manually

Set to maximum safe speed relative to rpm

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(These apply when the shifter is in manual 2nd)

[D0914] Manual Hold Gear 2nd 1->2
Generally the original values are 0 up until WOT Meaning that it starts out in 2nd and stays there until WOT

Set all values to 0

[D0919] Maximum speed that the PCM will stay in 2nd while the shifter is in 2nd before forcing the 2-> 3 shift

Set to out of range

[D0933] Manual Downshift Gear 3->2 Shift
Allows a downshift from any higher gear to 2nd with the column shifter

Set to maximum safe speed relative to rpm


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The reasoning behind this is at some point I plan on adding a ratchet shifter, getting this correct will render a little more control. Also I don't like the idea of the mechanical and hydraulic components of the transmission at odds with the tuning. zeroing out the [D0914] would just be too allow a 1->2 upshift at any given throttle position.

Has anyone ever tried this manipulation?

The reason I ask is because on the more electrical transmissions the manual valve controls the pressure manifold switch more than anything else.

Although I have gearcommand (Transgo HD2's clever little plug in the actuator feed passage at the end of the manual valve bore) the pesky 1-2 shift sometimes still occurs at part throttle.

Are these values what command that part throttle shift that sometimes occurs?

I am considering either taking up tuning or just getting my truck tuned and I'd like an opinion on whether or not what I have just suggested is wise.

Any input is appreciated.