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.

th400 shifting hard into 2nd?

Discussion in '1982-Present GM Diesel' started by protechk5, Dec 10, 2006.

  1. protechk5

    protechk5 1/2 ton status

    Joined:
    Sep 26, 2004
    Posts:
    2,015
    Likes Received:
    0
    Location:
    VA
    On my m1008 with 6.2 and th400 and 4.56 gears, if im on the gas hard it will shift pretty hard into 2nd, I can chrip tires, this isnt normal is it? Also it only stays in 2nd for like 3-4seconds, but i think thats b/c of the 4.56s. Any ideas?
     
  2. AKbigsub

    AKbigsub 1/2 ton status Premium Member

    Joined:
    Sep 9, 2005
    Posts:
    1,549
    Likes Received:
    17
    Location:
    Anchorage, AK
    My '90 with the 5.7l gas and TH400 does hits 2nd hard also. I kind of like it.
     
  3. dremu

    dremu Officious Thread Derailer Premium Member

    Joined:
    Feb 27, 2000
    Posts:
    15,966
    Likes Received:
    458
    Location:
    East of San Francisco
    TH400's are weird; they do shift by vacuum (which is even weirder on diesels) ... but the kickdown is electric and is notoriously unreliable on our trucks. They're also not adjustable. Well, they're not made to be.

    You might look on your gas pedal (err, accelerator :) ) and see if there's a piece of fuel line zip-tied around it, as that would kick the kickdown earlier ;)

    Alternately, could be an adjustable vacuum modulator, or could just be the way it works ... my CUCV is an '09, so it has 3.08:1's and ... well, it won't chirp sh!t :D

    -- A

    -- A
     
  4. imiceman44

    imiceman44 1 ton status

    Joined:
    Aug 5, 2002
    Posts:
    15,160
    Likes Received:
    1
    Location:
    Sacramento, CA
    I don't think that is normal, mine shifts smooth and I have 4.10 gears and 29" tires, you can feel it but it doesn't jerk or chirp, you just feel the a slight push.
    Maybe you are low on fluids, or the vacuum actuator is bad or you have a leak in the vacuum lines.
    I know when I had a leak in the vacuum it would shift late and hard like that.
     
  5. protechk5

    protechk5 1/2 ton status

    Joined:
    Sep 26, 2004
    Posts:
    2,015
    Likes Received:
    0
    Location:
    VA
    alright thanks, im going to check it out
     

Share This Page