Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Tranny Problem

Discussion in 'The Garage' started by Tannerman, Nov 4, 2006.

  1. Tannerman

    Tannerman Registered Member

    Joined:
    Aug 22, 2005
    Posts:
    13
    Likes Received:
    0
    Location:
    Canada
    Lately my tranny has been acting up. I am just driving along and the truck starts to buck, usually around 80-100 kms. I am thinking it could be the lockup on the tranny. Is there any way to figure this out, maybe disconnect the lockup? It doesn't happen all the time but is annoying as hell when it does. Truck is an '89 K5 with 350 and 700 tranny.
     
  2. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

    Joined:
    Dec 24, 2003
    Posts:
    4,395
    Likes Received:
    50
    Location:
    VA
    ''Starts to buck'' ? Violently or just barely noticeable. If it's just noticeable, check your fluid. Low fluid will keep cycling the lock up in and out. If it's violent it sounds more like a mechanical problem (read-rebuild)
     
  3. JEBSR

    JEBSR 1/2 ton status

    Joined:
    Dec 23, 2004
    Posts:
    1,541
    Likes Received:
    0
    Location:
    Clarksville, TN
    I have seen a lot of people condemn a trans for this problem when it was not the problem. If it is the lockup converter the tach will jump up and down when it locks and unlocks. Watch the tach and see if this happens. I have seen 4 trans. swapped for bucking and the problem was plug wires... I just wanted to mention this so that your sure your problem is the trans and not the tune-up of the engine.
     
  4. Tannerman

    Tannerman Registered Member

    Joined:
    Aug 22, 2005
    Posts:
    13
    Likes Received:
    0
    Location:
    Canada
    thanks for the replies. Fluid level is ok on the Tranny, checked that one. The bucking isn't terribly violent but it does make the tach jump about 600-800 rpm when it goes. The motor is rebuilt about 24000 ago and the wires are new not to long ago as I had a problem with the last set and one of the wire boots started to melt. I would say these Delco wires are about 10000 kms.
    What do you suggest?
     
  5. MaxPF

    MaxPF 1/2 ton status

    Joined:
    Apr 13, 2006
    Posts:
    2,207
    Likes Received:
    0
    Location:
    Chandler, Arizona
    Are you sure the fluid level is OK? Make sure it is good and hot, the truck is on level ground, and the engine is running with the truck in park when you check it.
     
  6. JEBSR

    JEBSR 1/2 ton status

    Joined:
    Dec 23, 2004
    Posts:
    1,541
    Likes Received:
    0
    Location:
    Clarksville, TN
    If the rpm's are jumping up and down that far it can't be in the ignition. Unplug the square plug on the drivers side of the trans and see if that fixes it. That will disable the lockup converter. If that fixes it then you will know where to start. If not the it will eliminate the converter.
     
  7. 1977k5

    1977k5 3/4 ton status Vendor

    Joined:
    May 26, 2003
    Posts:
    9,995
    Likes Received:
    131
    It CAN be in the ignition if the problem is the coil or ignition module. Those will drop spark to all cylinders if they are failing. If they work intermittantly, it would cut out for a few revolutions (the buck) and the tach would only be able to fall a few hundred RPMs before the spark picked back up.

    I had an ignition module go bad and it bucked and sounded a lot like this. I have a 4 speed though, so I looked right to the ignition to find the problem.
     

Share This Page