Results 1 to 7 of 7

Thread: 4L80E shifting issue

  1. #1
    Junior Member
    Join Date
    Mar 2010
    Posts
    26

    Default 4L80E shifting issue

    Problem is when I spin the tires off the line and get out of the gas it shifts to 2nd, then when I get back into the gas it kicks down to 1st, but then the trans never gets a command to shift back to second. The log shows that 2nd gear was not commanded to shift until after I got out of the gas bouncing rev limiter.

    On a good run with no spinning, the trans is shifting fine.

    Can anyone see what is going on with this setup? I am stumped....

    Thanks.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	Capture.PNG 
Views:	81 
Size:	68.9 KB 
ID:	16804  
    Attached Files Attached Files

  2. #2
    Junior Member
    Join Date
    Mar 2010
    Posts
    26

    Default

    The shifting problem happened again this morning. Car downshifted from 3rd to 2nd like it was supposed to, but never commanded a shift out of second until I got out of the gas. I did not notice this issue until I put the new gearset in the trans (2.10 first 1.40 second)

    From what I understand after a kickdown shift, the computer should use (2) tables to command a shift. (SHIFT at RPM D0940-D0971) (SHIFT at VSS, D0910-D0965). Both conditions are meet, but the log shows the PCM never commands the shift.

    What am I missing?

  3. #3
    Joe (Moderator) joecar's Avatar
    Join Date
    Apr 2003
    Posts
    27,808

    Default

    I'm looking thru your files...

    so it also missed the 2->3 upshift...? Do you have a log of this also...?

  4. #4
    Junior Member
    Join Date
    Mar 2010
    Posts
    26

    Default Shifting Issue Log

    Thanks Joecar! This stuff is driving me nuts!

    Attached is the log of the issue this morning. You can see in the screenshot the car shifted from 4th-3rd-2nd. Then held second until it bounced off the REV limiter, then I got out of the gas and it shifted.

    I hope this is just something I am missing in the tune.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	Capture_crop.PNG 
Views:	55 
Size:	58.6 KB 
ID:	16913  
    Attached Files Attached Files

  5. #5
    Joe (Moderator) joecar's Avatar
    Join Date
    Apr 2003
    Posts
    27,808

    Default

    I'm still looking at your files, but in the meantime try this: reduce the WOT RPM shifts down to 5000 rpm and do a test drive.

  6. #6
    Junior Member
    Join Date
    Mar 2010
    Posts
    26

    Default 1/8 Mile Run

    Here is another log of the car at the track a couple weeks ago. It had a personal best 60 ft of 1.35 with minor tire spin.

    If you look at this log, the shifts are also being commanded weird. The motor never hit the rev limiter on this run, however the 1st gear shift ran past 6000 rpm and 47mph which is were they should be commanded to shift. For 2nd gear the motor never reached 6700 rpm, (Unless you count the time it took to pull the motor down from the 2nd gear shift) but it shifted at the correct 104 mph.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	1.35-60ft.PNG 
Views:	52 
Size:	59.0 KB 
ID:	16918  
    Attached Files Attached Files

  7. #7
    Junior Member
    Join Date
    Apr 2010
    Posts
    48

    Default

    stop it shifting back to first in the kickdown (2-1 down shift)...they get lost in their modelling. Been through the same thing myself and only cure was to not allow it to kick down to first until like a low speed...

    Let me know how you go.

Similar Threads

  1. Need blackbox 4L80E tune for my 4L80E segment swap
    By Supercharged111 in forum 4speed RWD/FWD Transmission Tuning (incl T42)
    Replies: 52
    Last Post: September 10th, 2013, 09:57 AM
  2. 4L80E WOT shifting problem. 1st-2nd bounce rev limiter!
    By TransAm-Z in forum 4speed RWD/FWD Transmission Tuning (incl T42)
    Replies: 7
    Last Post: August 20th, 2013, 09:41 AM
  3. 4L80E Shifting Soft and Slow (tune attached)
    By LastCall in forum 4speed RWD/FWD Transmission Tuning (incl T42)
    Replies: 18
    Last Post: January 13th, 2012, 07:19 AM
  4. 4L80E shifting soft
    By BlackSS in forum 4speed RWD/FWD Transmission Tuning (incl T42)
    Replies: 0
    Last Post: November 19th, 2011, 03:05 PM
  5. 4L80E rough shifting issues
    By bekmwan in forum 4speed RWD/FWD Transmission Tuning (incl T42)
    Replies: 6
    Last Post: September 26th, 2009, 01:03 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •