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Thread: AOD Lock Up?

  1. #1

    Default AOD Lock Up?

    Working with my '84 GT350 once the AOD shifts into 3rd then 4th it will not unlock. Actually that's a lie it will but you absolutely have to smash the throttle for 5 or more seconds before it will down shift but will up shift and lock up almost immediately. Makes driving not all that fun.
    I installed a full 2.5" exhaust and in doing so I bent the linkage to the AOD. The linkage looks right, and I've done the TV adjustment by the book using a psi gauge. Approx 3#'s at idle and 35#'s off.
    Any help would be appreciated.

  2. #2


    Welcome to the site

    I'm not sure what you think "lock up" means, but it's not about shift points, or feel, or about "kicking down" a gear out of OD or something, but about the engine/transmission coupling acting as one, rotationally, eliminating the bit of slip there normally is with a standard automatic transmission's torque converter. Can we see a picture of whatever linkage you bent for installation of full 2.5" exhaust? CFI, EFI swap, carburetor? At idle, pressure should ideally be zero, with no slack and no tension at the (1:1 throttle and TV push/pull) throttle TV cable/rod, but 0-10psi has been stated as being OK. "Normal" acceleration should register on a gauge about 30psi, and WOT should register on a gauge about 80psi... if the problem is that it's not kicking down and putting a grin on your face, maybe there isn't sufficient pressure happening. What is it doing, or not doing, exactly?...
    Last edited by Walking-Tall; 12-31-2017 at 06:37 PM.
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website --->

  3. #3


    ^^^What he said.

    Additionally, in the AOD, both 3rd and 4th gears are direct couple, or 'lockup'. Lockup, when discussing and automatic transmission, refers to the bypass of the hydraulic coupling in the torque converter, and directly connecting the input shaft of the trans to the output of the engine crankshaft. This usually done thru a 'lockup' clutch, which an AOD does NOT have. Instead, the AOD has two input shafts, one splined to the turbine of the hydraulic coupling in the coverter, and the other splined to the converter housing, which is directly driven by the engine crank.

    Powerflow through the trans is as follows;
    The turbine shaft is directly connected to the forward clutch drum and reverse clutch hub. Direct shaft is connected to the direct clutch drum. Output shaft is connected to the ring gear of the planetary gearset. Planetary gearset is the ******aux type, with a forward sun gear, reverse sun gear, long and short planetary pinions, and a ring gear.

    1st gear; forward clutch drives the forward sun gear, planetary carrier is held by a one way clutch or low/reverse band (D/OD or M1). Forward sun drives the planetary gears, which drive the ring gear at 2.46:1.

    2nd gear; Forward sun unchanged. Intermediate clutch turns on, locking intermediate one way clutch to the case. Intermediate clutch holds the reverse clutch drum/reverse sun gear stationary (or the OD band holds the reverse drum/sun in M2). Forward sun gear drives one set of pinions, the reverse sun (held stationary) forces the other pinions to walk around it. This drives the ring gear 1.45:1.

    3rd gear; Direct clutch turns on, driving the planetary carrier. Since the carrier and forward sun are both being driven, all the gears are locked together, driving the ring gear at 1:1.

    4th gear; Overdrive band turns on, locking the reverse drum/sun to the case in both directions. Direct clutch drives the planetary carrier, and the planetary gears walk around the reverse sun gear, which causes the ring gear to be driven at 0.69:1.

    Hopefully this brief description helps you better understand what your trans is doing.
    Jim DeAngelis
    Cornucopia of Useless Knowledge
    Connoisseur of Dearborn Ferrous Oxide
    '83 GT hatch, currently under the knife

  4. #4


    Hey thanks guys for the info above. I had been listening to a Ford guy at work, he was saying the hydraulic lock up is where all the issues happen on a AOD.
    Any how, i will definitely be using the psi posted above as i do not think I'm best 80# at WOT.
    I have the shiftkit from TransGo SK AOD to be installed along with a governor as i read that it will definitely help shifting as well.
    When i install the intake manifold and carb i also have the Lokar kick down cable that will be installed at that time.

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