Results 1 to 5 of 5

Thread: 4l65 8K VSS nightmare

  1. #1
    Potential Tuner
    Join Date
    Aug 2019
    Posts
    3

    4l65 8K VSS nightmare

    I did an LS swap with a 4l65 for a friend of mine on an early Jeep. He wants to keep the stock speedometer, so we did the 8k ppm vehicle speed sensor.
    I have not been able to get the transmission to shift out of first gear.
    I am out of ideas.
    This is my set up.
    2005 GMC Yukon Denali 6.0 4L65E 4X4
    33 inch tires
    3.54 gears
    18 and 44 on the speed sensor gear.
    Here is my hpt file.
    Any ideas?
    Attached Files Attached Files

  2. #2
    Tuner in Training
    Join Date
    Sep 2017
    Posts
    28
    Use a Bluetooth OBD II adapter (inexpensive, maybe 15 bucks) and the free "Torque" app on your phone to see if the PCM is registering any speed. Use a helper in the passenger seat, this is a driving test.

    My 4L60E had a bad VSS and would not shift. Why would it? It thought it was sitting still. A new AC Delco VSS for a 4L60E was about $35. Not sure for your 4L65E.

    Rick

  3. #3
    Potential Tuner
    Join Date
    Aug 2019
    Posts
    3
    Quote Originally Posted by B52bombardier1 View Post
    Use a Bluetooth OBD II adapter (inexpensive, maybe 15 bucks) and the free "Torque" app on your phone to see if the PCM is registering any speed. Use a helper in the passenger seat, this is a driving test.

    My 4L60E had a bad VSS and would not shift. Why would it? It thought it was sitting still. A new AC Delco VSS for a 4L60E was about $35. Not sure for your 4L65E.

    Rick
    I monitored the output rpm and vehicle speed with my Snap On scan tool and both seem to be accurate.

  4. #4
    Senior Tuner Russ K's Avatar
    Join Date
    Dec 2005
    Location
    Regina, Sask.
    Posts
    4,152
    Just solved the same issue with a 1976 Sierra with a 5.3/4L60E with the OEM manual transfer case. Had a speed signal generator inline with the speedo cable. First got the scanner speed to match a gps, this is done with the "VSS Pulses Per Distance". Next log the output shaft RPM while driving. To calculate the trans mile per hour, do this; (trans output shaft rpm*60)/trans output revs per mile (which is 2,230.1949 in your tune)

    So you need to get the trans mile per hour to match the vehicle speed in the scanner, if the trans mile per hour is low, lower the "Trans revs/mile" by the % error of the vehicle speed in the scanner.

    Also look at you shift speed tables, your 1-2 is at 141 mph. What I did on the 1976 Sierra was to start with a stock tune, and change the tire size & gear ratio to what the truck has currently. Then copied all the shift speed & TCC tables to the modified tune.

    Russ Kemp

  5. #5
    Potential Tuner
    Join Date
    Aug 2019
    Posts
    3
    Quote Originally Posted by Russ K View Post
    Just solved the same issue with a 1976 Sierra with a 5.3/4L60E with the OEM manual transfer case. Had a speed signal generator inline with the speedo cable. First got the scanner speed to match a gps, this is done with the "VSS Pulses Per Distance". Next log the output shaft RPM while driving. To calculate the trans mile per hour, do this; (trans output shaft rpm*60)/trans output revs per mile (which is 2,230.1949 in your tune)

    So you need to get the trans mile per hour to match the vehicle speed in the scanner, if the trans mile per hour is low, lower the "Trans revs/mile" by the % error of the vehicle speed in the scanner.

    Also look at you shift speed tables, your 1-2 is at 141 mph. What I did on the 1976 Sierra was to start with a stock tune, and change the tire size & gear ratio to what the truck has currently. Then copied all the shift speed & TCC tables to the modified tune.

    Russ Kemp
    Thanks Russ,
    141 mph might be a little high for first gear lol.
    I don't know how that happened. I will fix the shift tables and report back.