727 Rebuild Blues

80fbody said
Ok. Could this input shaft be junk? It's about 10 thou smaller in the sealing ring area versus where the bushing rides below. I mic'd the new pump & it's the same size in the bushing as the the sealing ring area of the pump. Basically I think there's about 10-12 thou clearance at those sealing rings. You can certainly feel the step on the shaft just don't have another to compare right now.

That has nothing to do with your front clutch. The front clutch gets it's fluid through grooves cut in the stator (the part that bolts onto the back of the pump). The 2 sealing rings on the stator that slip inside the front clutch are what seals fluid (or air in your case since your at the stage of just air testing it) to the front clutch carrier. 30-35 psi is fine to use for testing. The trans. does run at a higher fluid pressure but air will escape much easier than fluid so any pressure higher than that will usually leak past. I assume you used atf or seal lubricant on the front clutch seals and sealing rings? If not you should have. Like Poisiondart said you don't have to install the pump and clutch packs to test them. Clamp the front pump down in a vise (with a cloth to protect surfaces) stator side up and stack the front clutch first then the rear clutch. Then you inject air into the proper port on the pump that leads to each clutch pack. Be warned that when the front clutch seals up the clutch packs will want to "jump off" the pump so hold them down. Sorry I don't have a chart that shows what ports on the pump lead to what clutch pack but just try each hole until you find the one that leads to the pack in question. These ports/holes I'm talking about are the ones that contact the trans case. Pressure is fed from the valve body through the case and the front pump to the clutch packs. As far as a possible parts mismatch, it's easy to tell if their not right because a 70 and older trans. used a 1/2" wide front clutch bushing and a 71 and newer used a 1" wide bushing. Measure the bushing in the front clutch pack that rides on the stator and compare it to the stator bushing surface. Should both be 1" wide since you said it's a 71 trans.