727 - Air Check - Not Going Well?

Been trying to get this BB 727 together, 1st build as I mentioned in a previous post. I'm just not happy with the "air check" on the front pack. I've tried it just on the pump & now twice bolted together. I just pulled it apart & changed the inner seal on the pack again. Lips are down.

At about 35 psi the rear pack has a good "thump" & then bleeds down. Now the front does have an okay "thump" but holds absolutely no pressure. It comes out as fast as it's going in. Tried to take a video of the "air check". Never tried to video with the phone before.

I did replace the complete pump (rebuilt unit) with the hopes it was just something there but no luck.

Would you tear it back down or close it up & hope it's ok?

Tear it back down... you have some issues

have you tried to prime the port with a little tranny fluid then air check it ?

if it was me i would have a pro trans builder check it out first,its not worth it to install it and have problems, and face this sight on your back on a creeper....dont ask me how i know...

I just tried to prime the ports with ATF but no luck. Also put another set of front clutch seals in & put it back together. No change. So what else could cause a severe air leak? Couple things. I bought this as a supposed running core a few years ago. Was not in very good shape when I opened it up. Had water damage in it but did seem to clean up ok. It's stamped 3674, i believe, which I translated to a 1971 core. That's what I've been ordering parts for.

I know some changes were made around 70-71. Is there anything there that could be screwing me up? Did any sealing rings change slightly, etc? I can mic it up if you guys have any direction.

Not following you on "air checking with the pump". I've always air checked using the ports toward the top of that pict with the valve body removed.

Since we can't see any of ur parts, might be time have a builder check things out. U could have nicked a seal or have installed the incorrect one. u never know.

air check

4 areas to air check

Could of rolled a lip seal in the high gear drun during assembly, some times they can be a real bear trying to get the seal past the clutch plate/disc retaining ring groove.

I always used to use lots of ATF ....

I just cleaned all the vasaline type assembly lube off the lip seals & re-assembled. Now that I've also learned I can install only the front clutch on the pump & air-check it's so much easier to see what's going on. Definitely better this time.

Going to get all new lips seals tomorrow & only use ATF on them this time. I think it may just give a better feel on the air-check.

There are only 2 points of leakage when air checking with the pump. The seals on the piston and the large diameter rings on the reaction shaft (back side of the pump) that seal the pump to the drum. Are there grooves inside of the drum where they ride? If the drum is worn, they're cheap. I just bought a new Dorman drum at my supplier Thursday for $32. That being said the front clutch is always lazier during air testing than the rear drum. And yes it's easier to air check with the pump rather than assembling the unit.
Doug

You know, that's it. It's lazyier than the rear clutch. That sums it up. Guess I really don't have an issue. Not knowing how it "should" act is my biggest problem. The drum isn't grooved & the rings fit nice. With new lip seals, I'm going to run it.

Thanks, that really eases my mind.

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I just bought a new Dorman drum at my supplier Thursday for $32.

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can you elaborate on that?