1999 Sierra 4l80 Hold gears on d1, d2.

[esteban20004298]

Overview. Its a 1999 sierra with swapped 4l80, 4l80 is built with Jakes 1000 hp capable rebuild, Jakes recalibration kit, and a 3500 rpm Circle D triple disk converter.
The truck will mostly be used for sand drags, and trails on sand.

I am trying tune the transmission so it holds 1st gear in d1 and hold 2nd gear in d2 in 2wd, 4hi, and 4low. I already did the D1 urban change and it still shift up.

D1 urban

1->2: 255 all the way across
2->3: 255 all the way across.

Let me know any ideas.

[Alvin]

Post the tune file.. We will have a look.

[esteban20004298]

99 Silverado SIlver original 6.0 4l80 modified tranny.hpt

[abc]

How are you selecting the different shift pattern when driving? Is there a selector in those old trucks?

My first thought, if you want it to hold first gear, you will need to put the selector in first.

Are they using the tow/haul button as the D1 pattern?

[esteban20004298]

Yes d1, d2, d3 on shifter.

I did put selector in first but still shift gear automatically afterit reaches certain rpm or speed.

I am not using tow haul.

[abc]

Yes d1, d2, d3 on shifter.

I did put selector in first but still shift gear automatically afterit reaches certain rpm or speed.

I am not using tow haul.

Log of the issue with all related PID's. Looks to me like it doesn't know you selected D1. As a test, run the full throttle 1-2 shift speed and rpm out of reach.

[Alvin]

I've been burnt by this before.. This looks like it is setup like it should work but obviously isn't.

Look up any corvette, GTO, or F-body etc file in the same year range. If you can find one with those matching tables copy it over. There are no cars that I'm aware of that did that safety shift stuff.

[RDF1]

Setup the tow/haul to only shift at the WOT RPM's mph.
You wont have engine breaking from being in manual 1s or manual 2nd but it works good for dirt drags.