4L60e has second gear only, can manually command 1st. Can't command 3rd or 4th

[cjsgarage]

hey guys.

I'm pretty competent around this tuning stuff, but this trans set up has got me really messed up. Contemplating buying a new-to-me TCM and ECM.. it's that bad.

The computers are flashed as an 08 Silverado with a 6.0.. I brought over all the ECM changes I could. (The engine tune still needs it own set of help--startup flare, fueling, timing, etc)

But my main concern is the transmission only ever commands second on its own, and will only take 1st manually. Will not take 3rd or fourth manually. It's an 08 transmission that's freshly rebuilt, with good fluid levels. Has the PRNDL wired up per factory, sans the orange wire to the ECM. No codes in the trans controller..

I did turn off the P0787 and disable the 3-2 downshift stuff just to make sure it wasn't forcing it into limp mode. No change. PRNDL displays correctly in the logs, but trans shift mode is unknown. Not sure if that matters. I also disabled the TUTD because sometimes it would show TUTD in the PRNDL position. Still, no change.


Anyone got any ideas on how to make this thing responsive?

Josh

08 silverado tune edited trans.hpt tune
drive 4.hpl a log

[cjsgarage]

I should add: it has a TCM that came out of a 2007 Saturn Aura. At least, that's what the paint marks on it say.

I can only assume the ECM came out of a 2009 Silverado, as that's what it was when I found it.
Since the trans wasn't an 09, I flashed it backwards to an 08 because I had the 08 working just fine with a similar set up.

This set up is an 2011 LS3/2008 4L70e in a 70 Chevelle.

[cjsgarage]

Anyone got any advice?

I swapped for an 08 ECM and it?s now reading trans current gear and PRNDL status. Trans Shift Mode is still ?Unknown: 0B?.

Still won?t shift out of 2nd on its own. Can command 1st gear and 2nd, but it ignores commands to go to 3rd or fourth. And doesn?t shift on its own.

[wax]

[QUOTE=cjsgarage;629999]Anyone got any advice?

I swapped for an 08 ECM and it?s now reading trans current gear and PRNDL status. Trans Shift Mode is still ?Unknown: 0B?.

Still won?t shift out of 2nd on its own. Can command 1st gear and 2nd, but it ignores commands to go to 3rd or fourth. And doesn?t shift on its own.[/QUOTE
I wish I could help but no one knows what the unknown bit is caused by. Im in the same situation myself

[wapp017]

Hi there. I got the same issue with a 09 silverado. The scanner shows the trans shift mode as unknown and won't change to 3rd or 4th gear.

I new in the tuning world and this is driving me crazy.

[kgraves]

Id suspect ECM and TCM mismatch. If the ECM was from a 2009, flashing a 2008 file onto the 2009 ECM with HPTuners wont rewrite everything. In my experience, a 2009+ E38 will not control a 2008 or older 4l60e. You would need GM software to reprogram the E38 completely.

[pzazzz]

Did you solve it yet? Is it giving a signal on the outputshaft in the transmission? I?ve read that it can stick in second if the sensor for output/inputspeed for the transmission isn?t working as it should.