2005 Explorer - 5R55S - Overdrive Planet sprag bearing fail

[expatexplorer]

It may be my lucky day. The trans started to slip and lose drive, eventually losing all Drive and Reverse, but I had low 1,2,3 to get me home slowly. I knew it was not a pump issue, otherwise I would have no drive at all and assumed it was probably a servo bore issue. During the tear down the overdrive planet would not come apart, so I assumed here is the problem. I managed to pry it apart and found the Sprag had failed and locked up the planet. Luckily the planet gears are undamaged and perfect so I will replace the sprag bearing and see how I go.

However, it does not make too much sense to me that if the overdrive planet locks up, how come I would lose drive and reverse, but not low 1,2,3? I pulled the pump apart and it is perfect, the trans was quite clean, a little material but nothing serious. I am still suspicious that it could be the torque converter failure, but lack of material in the trans pan or filter and working low 1,2,3 suggests not.

Does this make sense to anybody?

 

[JK080]

The planet may feel locked up to you but under the engine torque it most likely will slip and not hold and that's why you have the loss of gears.

However when I see this failure the planet and the intermediate shaft and hub will have damage and need to be replaced too. Look real close at these parts for damage or scoring from the sprag, anything other than a smooth mirror finish will cause premature failure. Also it looks like the bearing may be etching the front race surface of the planet and inside the hub. Small bits of metal from the bearing can get into the sprag and cause it to slip and fail, it might be best to replace all parts in this section.

I dont think anything would be wrong with the converter.