So when the 3-4 piston is applied, it also moves the overrun piston. (forward is already applied). How is the overrun clutches not applied? Does the 3-4 piston just not move far enough? Maybe the overrun springs are stronger than the 3-4 springs. Maybe I just answered my own question. Professionals please chime in.

 

It doesn't move the over run piston. It pushes the second gear servo to release the band and this also acts as the third accumulator.

 

It does move the overrun piston. If you look at the stack up, it's impossible for it not to. Plus I watched it do it. Don't know what you were answering with that second sentence. But thanks for the reply, I'll listen to any ideas.

 

The 3-4 piston does not apply the overrun. Overrun is only on in Manual d3, d2 and d1.When you air check it you may be getting some leakage in that circuit or you are missing the green o'ring on the input housing.

 

I know it's not applied unless in manual 321. I'm just saying it is moved by the 3/4 piston. ALL I'm asking is what keeps it from applying the overrun. Does it just not move far enough?

 

The 3-4 piston does not move the overun . The overun apply is in the forward clutch piston. Now it does move up with the forward clutch but still does not apply the overun.
The very first piston in the drum is the 3-4. Then you have the forward and overun in the next set and the 3-4 and those are isolated from each other. If the overun is moving when you apply the 3-4 you have a problem a leak as mentioned or perhaps you are confusing the forward clutch set with the 3-4?

 

Thats all I wanted to hear. I was hoping you would come to the rescue. thanks