Results 1 to 6 of 6

No upshifts (1995 Z28)

This is a discussion on No upshifts (1995 Z28) within the Automatic Transmission forums, part of the Drivetrain category; I backed out of the driveway, put the selector into Drive ... There was a slight hesitation (before going into ...

  1. #1
    Junior Member
    Join Date
    Aug 2007
    Location
    texas
    Posts
    4

    red
    1995 z28

    No upshifts (1995 Z28)

    I backed out of the driveway, put the selector into Drive ...
    There was a slight hesitation (before going into gear), then
    a "clunk" sound - very similar to the sound of driveshaft
    u-joint [cups] that are missing all the bearings - or as if
    you rev the engine slightly and drop the transmission from
    Neutral to Drive.

    I push on the accelerator and the car speeds up, but it never
    switches into 2nd gear (or any other gear). I stop, try again,
    this time letting my foot off the gas to "coax" the transmission
    into switching into 2nd. (reverse works).

    I drive back to the house and check the fluid - it's about 1 quart
    low, so I put in a quart - still same problem. (I had just driven the
    car home from the office and had it parked about an hour with
    no signs of issue).

    The only thing I did prior to leaving for the store: to determine if
    the compressor was not running because of too-low freon, I
    jumpered the low-pressure cycling switch plug to engage the
    compressor clutch.

    My thoughts for next step is to change out the tranny filter and
    new fluid .... and possibly "blindly" purchase the two shift
    solenoids (1st to 2nd, etc) and replace them while I have the
    tranny pan down. (no filter change in 50k miles).

    Any other thoughts/diagnosis?

    Thanks, Calder ...
    1995 Chevy Camaro Z28, 150k miles.

  2. #2
    Junior Member
    Join Date
    Apr 2007
    Location
    denton,Texas
    Posts
    27
    Couple things, are you sure your starting out in first and not third? If so you could have a blown fuse, I'd check there first ...second I would save the money on the selinoids, normally when one is bad you'll lose two gears, not three, ..I don't think changing your fliud will help either ..the sound of the clunk as you discribe it sounds like a hard part broke it's anyones guess other than that, I hope this helps ..Dave

  3. #3
    Junior Member
    Join Date
    Aug 2007
    Location
    texas
    Posts
    4

    red
    1995 z28

    Quote Originally Posted by Rock-On View Post
    Couple things, are you sure your starting out in first and not third? If so you could have a blown fuse, I'd check there first ...second I would save the money on the selinoids, normally when one is bad you'll lose two gears, not three, ..I don't think changing your fliud will help either ..the sound of the clunk as you discribe it sounds like a hard part broke it's anyones guess other than that, I hope this helps ..Dave
    Hi Dave .... I'm pretty sure it's driving off in 1st, since the car exhibits the same driving behaviour when i push down on the accelerator - it moves away quickly and the RPM's climb as if it's in 1st ... obviously, I anticipate it's about to shift into 2nd, but it doesnt.

    If I keep my foot on the gas, the car just drives down the street with the RPM's revving up and peaking - it's as if I have manually shifted the tranny down into first and left it there.

    Your comment about "are you sure it's in 1st and not 3rd" - does this relate to the fact that this tranny's "default" gear is 3rd? Seems I've read this somewhere - in what scenario does this happen?

    As far as changing the fluid/filter - I guess my thought is, "it's past due anyway, might as well drop the pan and check things out". Are you thoughts that the tranny is blown? I would have thought the car would have been acting up before that happens. I drive home and park it all is fine - next I get in and it's not

    Thanks -

  4. #4
    Junior Member
    Join Date
    Apr 2007
    Location
    denton,Texas
    Posts
    27

    hey

    There are several things that will default this transmission... when there is no power to the trans (blown fuse) it will default to 3rd gear, you can disconnect the power to this transmission and have both 3rd,and reverse gears.

    Now if your starting out in 1st, and it won't shift try pulling this transmission down to manual low and try manually shifting..

    Judging from your statement that you heard a clunk, like a u-joint, I would suspect a broken part inside the transmission. I think what your dealing with is a "broken hard part" A shaft, spline, drum, plantary, sprag ect. as examples. These are parts that are typically reused during a rebuild. This type of brackage isn't un common either and is all of a sudden. Again these are a few things that could break it's anyones guess.

    Pulling the pan will give you more information to go on for sure.

    Your right about one thing these cars do act up before going out , in a burn up scenario. normally 3-4 clutchs...Hope this helps Dave

  5. #5
    Junior Member
    Join Date
    Aug 2007
    Location
    texas
    Posts
    4

    red
    1995 z28

    failed speed sensor?

    I've had someone suggest I might have a failed speed sensor.

    Does the ECM depend upon the speed sensor *only* for shifting, or does it additionally rely on engine RPM and / or vacuum??? It would make sense that the ECM takes all inputs into consideration.

    Thanks!

  6. #6
    Junior Member
    Join Date
    Aug 2007
    Location
    texas
    Posts
    4

    red
    1995 z28

    fixed itself????

    Okay, now I am really confused.

    Yesterday, I disconnected both terminals from the
    battery - dont ask me why - I'm thinking that it will
    "clear the ECU" or something.

    Today, II hook it back up, start the car, re-check
    the tranny fluid level, back out into the street and
    put it into Drive, and it works! The car shifts up
    from 1->2, 2->3, and so on.

    There is still some sort of "soft clunk" when I move
    away from a complete stop - almost like something
    is loose or maybe it's the driveshaft. It's a very
    slight bump. Dos not happen in Reverse.

    One other thing - the tranny shifts "harder" going
    from 1st to 2nd. It always did exhibit the same
    behaviour as if a "shift kit" were installed, but it
    seems now it's a stiffer shift going into second.

    Is this a sign of eminent failure?

    One other strange thing. A few days ago, the A/C
    stopped working on the way to the office - after I
    got home, I checked the fuses, relay, etc. Nothing.
    The clutch would not engage. I jumpered the low
    pressure switch to coax the compressor to life.

    This is when I was going to the auto parts to get
    freon and the incident with the tranny not shifting
    out of 1st happened.

    So *now* the A/C works too (?!?!?)

    So if the tranny now works, which didnt 2 days
    ago, and now the A/C works, which didnt 2 days
    ago, is this a sign of a goofed ECU? Did
    disconnecting the battery somehow "reset" the
    ECU - I know it sounds crazy, but ... ?!?!?

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. 1995 t/a
    By Black beauty in forum General Help
    Replies: 2
    Last Post: 04-17-2013, 10:13 AM
  2. 1995 Z28
    By ford h8tr in forum Member's Rides
    Replies: 5
    Last Post: 06-16-2008, 01:37 PM
  3. Question: 1995 T-56
    By Julius in forum Manual Transmission
    Replies: 1
    Last Post: 05-27-2008, 10:00 AM
  4. 1995 Z28 for sale!
    By Racafella13 in forum Eastern Members
    Replies: 1
    Last Post: 04-26-2006, 05:44 PM
  5. HID kit 1995 TA
    By edr0ck in forum Appearance Section
    Replies: 2
    Last Post: 03-28-2006, 05:32 PM

Bookmarks

Posting Permissions

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