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  1. #1

    Default Replacing the reverse servo on an AOD

    Hello all,
    My AOD is slipping in reverse and drives as it should in low gear. I have been told that the reverse servo seal my have gone bad. Has anyone replaced the reverse servo in their transmission? Did you need or use a seal protector? They want $170 for a set of seal protectors that I'll may only use once. Has anyone had a similar experience with reverse? All the other gears in the trans work as they should. The fluid was nice and pink (I changed it anyway) and the pan had minimal sludge. Thanks for any advice.

    Tom

  2. #2

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    you dont need a seal protector for the servos there for the direct, forward, and reverse clutch piston seals

  3. #3

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    You mention that your trans operates as is should in low gear. I will assume, unless you tell me other wise, that you have engine braking. This would indicate that the reverse band, which is the reaction element, and its servo are operating correctly.

    Double check the operation of the trans in the L range. With the vehicle moving at approx 35mph, pull the shifter into the L range. you should immediately feel the trans downshift into 2nd gear. Engine braking should be felt. Allow the vehicle to slow down further, and you should feel the trans downshift into 1st gear, low range. More intense engine braking should be felt.

    There in another element involved with reverse gear in the AOD. That element is the reverse input clutch. It is not used for any other mode of operation in the AOD. If your tests indicate a properly working low/reverse band, then you need to look into the possibility that your problem lies with the reverse input clutch.

    Now, before others jump all over me, here; i should clarify. The reverse input clutch is only used in reverse gear, however, the O/D band clamps onto the outside of the reverse input drum in both 4th gear, and in Low Range 2nd gear. It is the O/D band holding the reverse input drum from spinning that gives the engine braking effect in Low Range 2nd gear.

    The Low/Reverse band clamps the planetary set and prevents it from spinning in both reverse and in Low Range, 1st gear.

    Let us know what your tests show, and we will go from there.

    Don
    Last edited by PrecisionTrans; 09-09-2019 at 11:38 PM.

  4. #4

    Default

    Thank you both for your replies. It seems that the transmission has other issues and needs a rebuild. Thank you again.

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