Missing gears on my AOD!

[Alexei]

Dear friends,

Yesterday when cruising, I lost my 3rd and Overdrive gears! Any thoughts of why, could this have happen?

Thanks!

 

[Sheriff41]

Did you check/set your throttle valve (TV) pressure when you installed the AOD?

 

[Alexei]

Yes, but, I will check again. What pressure do you suggest?

 

[Sheriff41]

I don't recall off the top of my head, but I know @mrgmhale posted a helpful video on setting the pressure.

 

[Alexei]

Perfect! Thanks a lot!

 

[Precision Transmission]

Sounds like the typical 3-4 clutch failure. The other possibility is the drive hub in the torque convertor for the inner input shaft has striped out. Used to see both quite frequently. Another possibility, but not common in a broken inner input shaft.

A way to help diagnose is to run down a hill until you are at a speed that allows the valve body to shift into OD. In OD, the fwd clutch disengages, and all input goes through the inner input shaft and the 3-4 clutch. With the fwd clutch disengaged, if there is no input though the inner input shaft and/or the 3-4 clutch, the trans will feel as thought it's in neutral.

 

[Alexei]

Sounds like the typical 3-4 clutch failure. The other possibility is the drive hub in the torque convertor for the inner input shaft has striped out. Used to see both quite frequently. Another possibility, but not common in a broken inner input shaft.

A way to help diagnose is to run down a hill until you are at a speed that allows the valve body to shift into OD. In OD, the fwd clutch disengages, and all input goes through the inner input shaft and the 3-4 clutch. With the fwd clutch disengaged, if there is no input though the inner input shaft and/or the 3-4 clutch, the trans will feel as thought it's in neutral.

Thanks!

If the 3-4 clutch is gone, should I rebuild the all the transmition?