Scratching my head. I’m thinking it’s tune related but I’m having no luck figuring it out. 2004 Silverado 5.3, circle D 3600 billet triple disc. 4l60e. Fully built. I have the sonnax hd 2-3 shift valve. I just put new gm solenoids in it and an aftermarket manifold pressure plate. He swears it always held 1st gear but I don’t remember. Maybe it did. I feel like it’s in the tune. If I put it in drive and take off from a dead, it shifts at the correct rpm (5900) on the 1-2 and 2-3. If I put it manual first from a say 20 roll, punch it and it shifts at 5000 no matter how I change the tune. Maybe I’m missing something. I’ve raised all the mph on the 1-2 in every table and I’ve messed with the urban D1 and the D1 settings. I’ve changed from 0mph, 256mph and 40mph. Noting makes a difference. I can post the tune if need be. Not by my computer at the moment. Any ideas?

 

Unless the tune was Adjusted to do it or it had the transgo HD2 it DID NOT HOLD MANUAL 1 . The factory tune makes the shift at a set RPM and or SPEED in all cases in manual low.
I do not have HP but in my TUNER CAT the M1 shift is a stand alone table Ill try and get a screenshot.
Now on I think 98 try changing the M1 table to 0 mph I wa told this works by someone once.

 

He swears it would hold out 1st gear with the shifter in 1st. I din't remember but i can get around it by using tow/haul as a race mode and make it drag first gear out to where we want. I'd just rather not do it that way.

 

No matter what he said, unless it was done in tune or with the HD2 kit ,, Cant happen .

 

heres the thing, Yes, there has been tuning done. Lots, by me. I do not remember what i've done so far, but without any tuning changes, he said it stopped holding out 1st. THE ONLY thing we did before it stopped holding out is I changed the fluid/filter, out new factory solenoids in and a new MPP but that was aftermarket.

I think I'm going to "fix" it with tow haul for now. I can set it to hold first out when the shifter is in third and the button on. I'll allow him to go from a 20 roll and it'll shift automatically.

 

This is what the table looks like in my software

 

last night I put the 1-2 and 2-1 at 0 but I haven’t tried it yet. I’ll try that and then try yours. I haven’t tried it your way just yet. Thanks. I’ll report back.

 

You know I Just remembered something that happened on the DYNO once, I had one that when i would max the line it would shift 1-2 even in manual low with both solenoids ON and it was not a glitch as they were turned on with toggle switches,
Ultimately it was the solenoid its self as we changed it and the situation was fixed, These were NEW GM SOLENOIDS, We PUT A set if good used in and it fixed it. We then tried another set of new and it again upshifted at max line. So we put the good used back in which were like new and sent it,
I could find no issue with the solenoids but they were the issue. Of note we did not run into it again on another unit running the same solenoids, So I do not know unless the AFL somehow over powered the new solenoids and the 1-2 dumped.
Just something That popped into my head was a number for years ago, If in data its not showing the shift commanded that might could be something to consider.