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th400 gurus

Discussion in 'The Hokey Ass Message Board' started by kyle paul, Nov 20, 2008.

  1. so i have a th400 I'm my car. i got it used and it wont lock in park from what i understand the whole park setup is mechanical correct me if I'm wrong . but my question is what all would keep it from locking ?i can roll the car in park and it just clicks i.i know the parking paw isn't locking into place but what could be the cause ? Ive pulled the pan 3 times now all 3 times the trans would lock in park and work fine for like a day the stops locking . any info would be great even a online rebuild chart .. as i dont want pull the pan again after this ..thanks
     
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 46,486

    squirrel
    Member

    Start with the shift linkage adjustment....what kind of shifter do you have? did it used to work and then started acting up, or has it always had trouble?
     
  3. the linkage is fine . i also pulled off the linkage and put it in park by hand and it still does it . it was doing it i took it apart checked it out then it started working for like a week now its doing it again
     
  4. sounds like the lock pin is broken
     
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  5. squirrel
    Joined: Sep 23, 2004
    Posts: 46,486

    squirrel
    Member

    Pretty hard to say without looking at it. The tooth on the parking pawl could be rounded, the teeth on the planet carrier that it meshes with could be rounded off, the retainer could be installed wrong, the spring loaded gizmo on the end of the park rod, that pushes against the pawl, could be messed up.
     
  6. Pir8Darryl
    Joined: Jan 9, 2008
    Posts: 2,489

    Pir8Darryl
    Member

    Yea, what squirrel said... :D

    Sounds like the previous owner slammed it into park from a hard roll a few times and either bent or rounded off... Or just plain broke a critical component. Unfortunately, it could be one of about a dozen things.

    It's been a couple years since I'v been inside a T-400, but if I remember right, almost all of the parking mechanism can be acessed thru the pan and valve body.
     
  7. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,098

    d2_willys
    Member
    from Kansas

    Are your motor and transmission mounts ok? Just a thought, perhaps after driving the car the engine position has moved and affecting the linkage enough to come out of park position.
     
  8. squirrel
    Joined: Sep 23, 2004
    Posts: 46,486

    squirrel
    Member

    Sounds like it's not a mount or shifter problem....
     
  9. haymaker
    Joined: Apr 29, 2008
    Posts: 97

    haymaker
    Member
    from Enid, OK

    I would look close at your park rod on the end where it engages into the pawl. You can also look up in there and see the teeth on the rear planetary it is possible that just a few are screwed up thus resulting in your working ok for a day or two. Also make sure that the rooster comb is all the way on the manual shaft, it has two flat spots on the side that hold the comb in position on the shaft. Best of luck and unless the rear planetary is fubared you can fix any of that by pulling the pan. And yes I know exactly how frustrating it is to have to pull the pan off the same vehicle over and over. I grew up and continue to work in a transmission shop.
     
  10. Good info.

    Not trying to highjack here, but I'm wondering what's the best way to check T-400 fluid levels?

    In drive, engine idling and warm seems to work best.

    Reason I ask is, I don't know where the hell I should be with the Lokar flexi plastic dipstick.
     
  11. In park or neutral, not drive.
     
  12. LUX BLUE
    Joined: May 23, 2005
    Posts: 4,408

    LUX BLUE
    Alliance Vendor
    from AUSTIN,TX

    it doesn't have the skooshed in hash marks?
     
  13. Rabid Whippet, I'll give that a shot in the morning.
    Probably got the "in drive" bit from my old 67 Cuda.



    Yeah, but it is either so low that it wants to slip in reverse, sometimes drive and if too high it pukes some ATF overboard.

    When the level is correct, the trans operates as it should.

    Bad part is, the puky area is right over a collector.

    I probably lost more ATF than I thought during a diff swap that required removing the housing and also when I thought that enough oil was out that I could swap speedo gears.

    Nothing quite like a half-quart or so right down the sleeve of your sweatshirt....
     
  14. squirrel
    Joined: Sep 23, 2004
    Posts: 46,486

    squirrel
    Member

    you should be in a different county than the lokar junk dipstick, get a real one! (oem)

    Usually it will slip when you first put it in gear, if it's about two quarts low.

    Check when it's warm, idling, in park, but after you've run the shifter thru the gears.
     
  15. Lokars are great in certain applications. You could pull the loKar out and feel where the fluid level is. I believe the fluid should be at the gasket level. Since the lokars just slip in and are flexible it should be pretty easy. The newest designs have 2 o rings and then theres one that actually has a nut on the insid of the pan. Hope it isnt the last type or the pan will have to come off.
     
  16. The Lokar I have is an older single O-ring model.
    Push-in model.
    I machined in a 2nd groove and that cured the leaking problem from that area.


    When I was building the car I bought a chrome plated stock style all steel dipstick and tube.
    It wouldn't fit even if I bent it moderately.

    I had a short Lokar in it originally, but went to the longer model.

    If the chrome plated stock type dipstick and tube doesn't fit the 31 I'll make one of my own.

    There's room to cut a hatch in the floor for dipstick access and filling.

    I'm curious as to how much pressure is in the trans cooler lines?
     
  17. squirrel
    Joined: Sep 23, 2004
    Posts: 46,486

    squirrel
    Member

    Chinse chrome plated junk is not OEM either.

    Not a whole lot of pressure in the cooler line, but when you head down that last hill towards hoover dam (from Kingman) and it pops off, life gets interesting! that's how I learned the be-sure-to-bubble-the-steel-line-before-you-put-rubber-hose-over-it rule.
     
  18. Thanks guys.

    I think the chrome plated piece is a factory GM part.

    It was purchased circa 1985.

    I know that my pals about five years old chrome trans dipstick leaked like a sieve
    Pretty sure it was Chinese made.


    I wonder if Chinese fighter pilots wonder about the quality of their aircraft when they're cranked over in a hard turn.

    Probably not since they'd be limited to 2G's at most with their copycat airplanes....
     
  19. F.O.G
    Joined: Oct 31, 2006
    Posts: 259

    F.O.G
    Member
    from Pacific,Mo

    Sounds like the rooster comb has rounded the flat spot on the shaft or as
    was stated someone jammed it in park while moving, Check the 9/16 nut that locates/locks the rooster comb to the shaft,could be loose.
     
  20. LUX BLUE
    Joined: May 23, 2005
    Posts: 4,408

    LUX BLUE
    Alliance Vendor
    from AUSTIN,TX


    I will see Your "own personal oil slick" and raise You a "Geyser of hot coolant"

    On the back of an Olds intake, the heater valve screws directly into the manifold. If You have no heater, You don't need the valve, right?
    Mr. Hacksaw to the rescue. whilst the tuning commenced, the hose slipped (edit-SHOT) off and presto! a 14 foot tall geyser of the green stuff. Nice and HOT, too!
    You have never seen 3 guys get out of thier shirts that fast in Your life.( I hope.)
     
  21. LUX BLUE
    Joined: May 23, 2005
    Posts: 4,408

    LUX BLUE
    Alliance Vendor
    from AUSTIN,TX

    Have You made sure the vent tube is clear and clean? a little resistance there and it will force a tans to "burp" out the dipstick. doesn't have to be all the way clogged, either.

    I HATE dirt daubers for this reason alone.
     
  22. squirrel
    Joined: Sep 23, 2004
    Posts: 46,486

    squirrel
    Member

    It is possible that the chrome dipstick/tube is an AC Delco branded chinese part...but it's not a Factory GM part.
     
  23. ok so i fliped the bracket around that holds the rooster comb in place and now it works fine but the bracket is backwards .i checked a other trans and it s not right but works .. gonns change it back tomorrow just wanted to see what would happen before i left the shop
     
  24. Lux Blue, you were right on about being two quarts low.

    Didn't think I spilled that much.


    I'm guessing it's ok to check the vent tube with a short piece of mechanics wire or even the pointed end of a Ty-Wrap.

    I forgot to mention that Lokar now makes their trans dipsticks with two O-rings.
    In answer to a leakage problem with the single O-ring setup.

    I need to dig out that stock (?) plated dipstick and see if it fits and decide about the O-ring.

    Making a 'billet' plug, cutting off the end of the plated dipstick and JB'ing them together looks workable.

    So does using a speedometer cable, some #4 stainless braided, making a couple of aluminum adapters for each end is a do-able deal.

    Thanks for the help.
     
  25. TMcCrea
    Joined: Aug 13, 2008
    Posts: 583

    TMcCrea
    Member
    from Maryland


    In addition to the items already mentioned, you could check for something as simple as a loose bracket that holds the parking rod against the pawl. It is held in place with two bolts and could have been improperly tightened at some point. If the bracket is loose, it will not hold the rod close enough to the pawl to fully engage.
     
  26. thats the brackett i took off and reversed .. it works fine with it reversed but i know it s on wrong now i matched it up too a manual and another th400. what will happen if i run this bracket backwards
     
  27. TMcCrea
    Joined: Aug 13, 2008
    Posts: 583

    TMcCrea
    Member
    from Maryland

    To be installed properly, the bracket has to have the "hump" against the tapered end of the rod so that it is in contact with the pawl. The "large OD" part of the rod is what holds the pawl engaged to the rear planet carrier when in park.

    Aside from putting the trans in park while rolling, the only engagement problems I have seen are the loose bracket or improperly adjusted linkage. Of course, a loose rooster comb can cause the problem also. Sorry I don't have a photo to illustrate.
     
  28. TMcCrea
    Joined: Aug 13, 2008
    Posts: 583

    TMcCrea
    Member
    from Maryland

    Forget about the "hump". I must have been thinking about the bracket on a 700R4. Found a photo that illustrates the correct installation. Just keep in mind that the rod has to go full travel to the rear and the large OD part of the taper has to contact the bracket and pawl.
     

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