I'm rebuilding a 727 and am to the point where I am checking the servos for leaks with air pressure and it seems like the low/reverse servo applies much harder than the kickdown servo. Is this normal? I've replaced the sealing rings and checked their fit and they were fine. Any suggestions? Thanks.

 

Did you use any lub on the cyl. when you put the piston in? It's been a while since I did a air check .I use to make my band adjustments and then at the end just before the valve body went back on , I used a air gun with a piece of fuel line clamped on the tube so as to make a tight seal against the case . Then slowly apply air to watch the action of the band and servo's.Also listened for air. Then the clutch pack's. Hope that helps you. Wish I could see and hear what your doing I could tell you in an instant. Let me know if you need any more tips. Cert. Trans repair was my job when I worked at the dealerships. When Mopar had Great Trans. 727 and 904.

 

I used trans assembly lube. I figured the applying action isn't as solid as the rear band because the low/reverse servo uses a lip seal and the KD uses sealing rings.