Page 5 of 5 FirstFirst 12345
Results 81 to 93 of 93

Thread: Hesitating/slow shifts... bad tune?

  1. #81
    Tuner in Training
    Join Date
    Apr 2008
    Posts
    28
    Where would one procure such a spring?

  2. #82
    Tuner
    Join Date
    Feb 2008
    Location
    Litchfield Park, AZ
    Posts
    77
    Quote Originally Posted by Russ K
    Raising the WOT shift points will put you back to tune J.
    So if I understand correctly, the only reason the shift is firm with the current tune is because it is occurring at a lower RPM? Am I correct in assuming you suspect there is a line pressure issue at high RPM?

    I look forward to seeing what the transmission shop has to say about the matter.

    In the meantime, Russ, would you be willing to set up a tune with 5500rpm shift points like you recommended?
    Last edited by big_news_1; 09-18-2008 at 10:30 PM.
    '97 Bonneville SE/SLE L36

  3. #83
    Tuner in Training
    Join Date
    Apr 2008
    Posts
    28
    Sorry to be a pest, but this concerns and interests me. Are you saying the only thing you've done to "firm up the shifts" is drop the RPM until the transmission has enough pressure to actually shift and hold? I'm seeing results, but the method to the madness needs to be understood so that this doesn't happen again in the future, and if it does, we have an idea of what route to take. That is, of course, unless everything you're doing boils down to trade secrets and experience. It's the process of thoughts you're going through I'm trying to learn.

    Given there is not enough pressure at the higher RPM's, you mentioned a spring. This spring is of particular interest. Maybe I can't get a "better" one to install, but a stock one that can be modified to work better than stock?

    A little knowlege is a dangerous thing. So I'd like to know more.

    Don't get me wrong, results are great. I think understanding is an important part of those results though.

    Thanks
    Last edited by mylittleblackbird; 09-22-2008 at 10:42 AM.

  4. #84
    Senior Tuner Russ K's Avatar
    Join Date
    Dec 2005
    Location
    Regina, Sask.
    Posts
    4,213
    Like I said before, the line pressure needs to be checked. Also I mentioned to call Transgo for more info about welding a spacer to the modulator valve to help raise the line pressure. But most likely, a stiffer pressure regulator spring will be required. I did a search, and only Transgo has any kit of a shift kit available for the 4T60E trans.

    This trans needs to shift firmer at WOT, in order to shift quicker.

    Russ Kemp

  5. #85
    Tuner
    Join Date
    Feb 2008
    Location
    Litchfield Park, AZ
    Posts
    77
    The car was dropped off at the tranny shop about 1 hour ago. By the end of the day I should have a report of the line pressure, electrical connections, and general functionality of the tranny. We'll see what they have to say.
    '97 Bonneville SE/SLE L36

  6. #86
    Tuner in Training
    Join Date
    Apr 2008
    Posts
    28
    Sorry I overlooked the "call transgo" bit. Thanks Russ

  7. #87
    Tuner
    Join Date
    Feb 2008
    Location
    Litchfield Park, AZ
    Posts
    77
    The transmission shop said everything "seems alright" with my car. I even flashed tune revision "J" to the PCM so they could experience the slow WOT shifts. I don't get how they couldn't see the issue!

    They weren't able to test line pressure while driving, so basically they just checked it while sitting in the shop. They said their line pressure test showed everything normal, which might be the case at idle. However, all the scans indicate low RPM line pressure is fine while high RPM pressure is an issue. We can't know for sure without testing at high RPM. Other than that, they said all the electronics seem to be fine.

    We obviously need to look into Russ' suggestion of increasing high RPM pressure. A few questions:

    1. Is there one dedicated pressure spring which will increase pressure all-around, or are there individual springs for each shift?

    2. Would increasing pressure for high RPM make overall pressure at low RPM dangerously high?

    3. Might there be an issue with my pump if pressure is falling off above ~5500RPM? I know the 4T60 pump is less efficient than the 4T65, but I thought it would maintain suitable pressure up to 5800-5900RPM.


    Many thanks, guys! And Russ, I continually appreciate your guidance in this matter. You've been integral in helping me understand the problems we're dealing with.
    '97 Bonneville SE/SLE L36

  8. #88
    Tuner in Training
    Join Date
    Apr 2008
    Posts
    28
    We need to call transgo about the spring thing, I guess. I'd much rather look at a vac modulator, and see how exactly it functions when placed under vacuum, and modify in small amounts from there.

    Then again, I'm nuts.

  9. #89
    Tuner
    Join Date
    Aug 2004
    Location
    Chandler AZ
    Posts
    117
    So if you completely remove the vac line from the modulator then your at full pressure right?

    Test that.
    Remove the vac line from modulator.
    Plug the vac line so the engine doesn't ave a vac leak and test.

    I have a vac modulator laying around here, I'll go test it with and without vac and see which direction it moves. Depending on the results it may be something that can be removed completely and plug the hole or add a washer to the end of the plunger for increased line pressure.

    Ben... what's going on with your car...??? it just seems like something else needs to be found.
    Best 60' = 1.716
    Best ET = 12.186
    Best MPH = 112.98


  10. #90
    Tuner in Training
    Join Date
    Apr 2008
    Posts
    28
    the test has been tried to no avail if I recall. If the screw is closed, it's running full tilt anyways.

  11. #91
    Tuner
    Join Date
    Feb 2008
    Location
    Litchfield Park, AZ
    Posts
    77
    We're starting to think about electrical again.

    My battery (new within the last year) consistently tests low voltage. The alternator is known to have a shoddy positive connecting stud, though it seems to be holding pretty good at the moment. However, idle tests at the parts store indicate a barely-acceptable alternator output. Also, the radio and climate control go on the fritz from time to time. The dash gauge also reads no more than 12v at any time, often dipping down to 10v-11v.

    Perhaps the shift solenoids aren't getting enough juice? We already know that the PCM is commanding shifts at the correct RPM but the transmission isn't responding until 400-600RPM later.
    '97 Bonneville SE/SLE L36

  12. #92
    Tuner in Training
    Join Date
    Apr 2008
    Posts
    28
    So, Ben. What did the tranny shop say?

  13. #93
    Tuner in Training
    Join Date
    Apr 2008
    Posts
    28
    I hate to be persistent but to my recollection, the tranny shop said that the line pressure was too high. I believe it was said they adjusted the modulator to decrease the line pressure but it was still at ?130ish psi? We do not know what position the gear selector was in. So... That said. Any thoughts?