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.

Fresh TH400 lost all forward gears but good reverse?

Discussion in 'The Garage' started by 6.2puller, Feb 13, 2007.

  1. 6.2puller

    6.2puller 1/2 ton status

    Joined:
    Jul 8, 2004
    Posts:
    569
    Likes Received:
    0
    Location:
    New England
    OK I have a TH400 in my V3500. I rebuilt it about two months ago. IT has under 1000 miles on it. The other day I added a tranny cooler and fixed a coolant leak. Got in and no more forward gears. It isn't even trying to engage. Reverse works great. Thuds right in and off we go backwards :haha:

    So I am hoping this is something stupid and easy that can be resolved without removing it from the truck again. Any ideas?
     
  2. Jason4x4

    Jason4x4 1/2 ton status

    Joined:
    Nov 5, 2006
    Posts:
    4,505
    Likes Received:
    6
    Location:
    Chandler, AZ
    If you added a trany cooler, did you refill the trans?
     
  3. 6.2puller

    6.2puller 1/2 ton status

    Joined:
    Jul 8, 2004
    Posts:
    569
    Likes Received:
    0
    Location:
    New England
    Yes sorta. I was trying to give it a test run to warm the fluid for a final check. Their is enough fluid to hit the dipstick add mark when cold.
     
  4. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

    Joined:
    Dec 24, 2003
    Posts:
    4,395
    Likes Received:
    50
    Location:
    VA
    Ouch, my 350 did that when it broke the lip on the forward clutch that holds the big circlip. That was another rebuild! I had 400 miles on that. I think it was the shift kit giving tired old parts a hard time!
    I hope yours is better news!
     
  5. 6.2puller

    6.2puller 1/2 ton status

    Joined:
    Jul 8, 2004
    Posts:
    569
    Likes Received:
    0
    Location:
    New England
    Anybody else got a guess? Maybe even something I can try without removing the tranny again. :D
     
  6. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

    Joined:
    Dec 24, 2003
    Posts:
    4,395
    Likes Received:
    50
    Location:
    VA
    Drop the pan. If it is the forward clutch there'll be shrapnel!
    If you have pressure gauges you could check line pressure through the gears.
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,982
    Likes Received:
    190
    Location:
    Roy WA
    You can try manually running through all forward gears while giving it some gas. Not sure exactly what this "unsticks", but I had a TH400 that after rebuild wouldn't go into 3rd gear a couple of times. Asked a transmission builder friend about it, he suggested when it's doing that, go through all forward gears MANY times, and eventually it did work, and the problem never returned.

    Seems a bit odd with no forward gears, if you check out an ATSG service manual, it may even list your specific problem and cause. Don't have mine handy or I'd look.
     

Share This Page