I have plenty of reverse, no forward gears

Discussion in 'The "Juice Box"' started by mineseats9, Dec 3, 2020.

  1. mineseats9

    mineseats9 Gold Level Contributor

    I picked up a ‘69 Skylark that has a fresh 455, and a rebuilt ‘73 400 trans. The engine was rebuilt 10 years ago and runs great. The trans was rebuilt 10 years ago as well by Aamco transmissions as a “carry out” and installed along with the engine by the previous owner. The car was ran briefly to break in the engine and the only drive time it had was out of the garage into the driveway and back in the garage one time. The car sat for 10 years in a dry garage after that and I bought it. Got it running and had it up on stands, put it in drive and had little to no action in any gear. Checked fluid level and it was very low. Topped off the fluid and the car would go into reverse pretty solid and barely spin the tires in drive. On the ground the trans goes into reverse real solid and moves the car like it should, in 1, 2 and Drive I get close to nothing. Linkage is working like it should. Just looking for any opinions on what to check before I pull the trans. I have not dropped the pan yet because I still want to be able to push the car out to the driveway and back it up the slope into the garage and fluid is expensive. I’m pretty sure the trans needs to come out but I’m looking for anything I may be missing? Thanks
     
  2. Matt69olds

    Matt69olds Well-Known Member

    Put a pressure gauge on it, see what the pressures are in each forward gear. Sounds like something I’d screwed up with the forward clutch.
     
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  3. Jim Weise

    Jim Weise EFI/DIS 482

    I would suspect an issue with the forward clutch. A TH 400 is a "clutch stacking" trans. Without getting too deep in the weeds on powerflow, one just needs to understand that the forward clutch is first gear, the intermediate is second, and the direct is third.

    Reverse is a combination of the direct clutch and the low/reverse roller clutch in the rear gear train.

    When I say clutch stacking, what I mean is that in drive range, first gear, the forward clutch is energized. This clutch stays on during all subsequent gear changes, we just add clutches to manipulate the planetary gear sets, to do our bidding.

    So with no first gear, we look first at the forward clutch.

    In a situation like yours, where it was built and worked, but now does not, after sitting a long period of time, I would suspect the forward clutch piston to be stuck.. due most likely to corrosion...transmissions must be stored in a dry environment, they do poorly in cold climates with unheated storage.

    Good luck

    JW
     
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  4. Bens99gtp

    Bens99gtp Well-Known Member

    Good thing is the forward clutch is pretty easy to get to......you know the direct/reverse clutch is working.......
    Once trans is pulled remove pan....remove pump bolts......remove pump by using a pry bar up behind the pump on the pressure regulator housing....normally take very little effort to slide it out psst the o ring......I like to scribe a mark inside the case by laying a small pick or driver blade as flat onto the clutch drum as I can......this helps verify proper install.....grab the input shaft and slide the first drum out.....take to tranny shop....

    sounds like a cut lip seal seeing you are getting some minor movement when off the ground
     
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  5. mineseats9

    mineseats9 Gold Level Contributor

    Thanks, this car was stored inside and dry but not climate controlled. So it went from extreme cold to extreme hot and humid for quite a few years. Appreciate the input.
     
  6. mineseats9

    mineseats9 Gold Level Contributor

    I will also add that I bought this car for the engine and trans for another project. Although everything is coming out anyway, it would have been nice to take the car for a drive first. Thanks for the replies.
     

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