I'm just finishing assembling my 727. It's the first time I've ever rebuilt a 727, so I'm not sure what to expect during an air-check. I air-checked both clutches before I installed them in the transmission, and they seemed OK, although I did hear some air leaking. Moving the clutch assemblies around on the shaft seemed to change the sound of the leakage and even nearly eliminate it, but at 40 psi, the "clunk" of engagement was pretty light. When I upped the pressure to 70 psi, the "clunk" was much more pronounced, although I could still hear some air leakage. I'm using Teflon rings, which I hear are difficult to get to seal properly, so I removed them and replaced them with the old steel rings. At that point, the air leakage was reduced and I could get the clutches to "clunk" at the lower pressure (about 40 psi). I was satisfied with this until I installed the inards of the trans. and the pump. When I did the final assembled air-check through the case, I got an even lighter "clunk" from the clutches.

I'm pretty sure I assembled the pistons/clutch packs correctly, and I've replaced all the bushings and experimented with different rings to get better sealing through the shaft. I can definitely notice a difference at higher pressures (higher pressures give a stronger "clunk" and reduce the air leakage sound).

Do you guys think I'm OK? I wasn't expecting to hear air leakage, and I thought I should get a stronger "clunk" at lower pressures. But, like I say, this is the first time overhauling a 727, so I really don't know what to expect.

I had a SB 727 that lost 3rd gear and when air testing the trans the front clutch pack sounded like a hurricane (compared to the rear one), so I replaced the rubber seals and it solved that problem. Difference between the front and rear was significant, but after the seals were replaced the leakage appeared equal. Yes, there was some leakage, but the clutches engaged with a "thump." I think with fluid, the leakage will be reduced. I thnk you'll be OK.

I hope you replaced the rubber seals on the clutch pistons? I use an old paint can as a stand to hold the front pump, then install the front clutch assembly. Apply air to the hole in the pump housing to air check the front clutches. I usually check the clutch clearances with a dial indicator this way too. Then you can install the rear clutch assembly, and air check it the same way, but the air pressure will want to raise the whole assembly, so don't use alot of air pressure. Too much pressure to the rear clutch could also damage the spring.

I did replace the seals and air-check the clutches with them on the pump support before assembly. They engaged better in this test than they did when the trans. was assembled.

A little bit of air leakage is OK, your looking for a massive flow of air before condemning it. To minimize the air leakage try squirting some ATF down the hole before applying the air pressure.