Results 1 to 2 of 2

Thread: L33 / 4L80 / Holset HX55 turbo - Completely stock transmission HARD 1-2 and 2-3 Shift

  1. #1
    Tuner in Training
    Join Date
    Dec 2013
    Location
    Indiana
    Posts
    28

    Stock transmission too firm 1-2

    Guys I had a post in the engine section by mistake, seems this is the more appropriate area.

    I did this swap years ago and only recently swapped back to an automatic. Was a T56. Tune was hacked up by wait4me before I learned better..

    The trans I put in is COMPLETELY stock.. No stall, no kit (to my knowledge), Nothing but fresh fluid and a good cleaning. Pulled from an 09 3500 ATT van so I assume he didn't have an HD2 kit in it.

    WOT performance is on point.. it shifts firmly and runs great..

    HOWEVER, driving around town the 1-2 and 2-3 are very firm.

    The ECM and tunes in the ECM are from an 06 truck. Both GMC.. I initially posted my tune and log in the other section and a person noted that my trans temp was stuck at -28F so I found a bent pin and have since fixed that.. Shifting hasn't gotten any better.

    Shift timing points can be tripled and it doesn't seem to make any difference.. I don't fully understand how to make line pressure tweaks to make it shift softer and I also don't fully understand how to log trans pressure.. I don't think I have it in my log file and can't seem to find anything thats name makes sense to me.

    EDIT: Found the issue to be one pin out of place in my harness that controlled the trans pressure solenoid. All is well - trans shifts like butter at light throttle now but is still firm enough on the high end.
    Last edited by IG109; 01-18-2020 at 07:59 AM.
    My Garage:
    2013 Challenger R/T
    2013 Caprice PPV - Dad car

  2. #2
    Advanced Tuner
    Join Date
    Dec 2011
    Location
    San Antonio, TX
    Posts
    319
    Not at my laptop with HPT so can't look at files... but assuming you're running SD only with failed MAF? If so, look under trans diag. there should be some switches for max line pressure with certain codes or faults. Check that.
    JTC Performance - Authorized HP Tuners Reseller
    Remote performance tuning