Hey all,

I am in the process of rebuilding my AW4 and have finished installing all of the rotating assembly. Per the manual, I have applied air pressure to the feed holes to confirm piston movement/clutch engagement. All of the pistons can be heard engaging the clutch packs, but I can hear blowby during testing of the direct clutch and forward clutch. I realize the pressure is maintained via split seal rings on the overdrive support (pages 63 and 94 of the AW4 manual give a decent breakdown of what I am talking about), but I imagine that those soft seals were not designed to hold back all of the pressure. The rings are new and I imagine they may grow once exposed to tranny fluid for a period of time, though I did coat them generously with petro jelly.

Is this blowby okay/expected as long as the pistons are engaging? I had to apply 90 PSI of air pressure to get the desired engagement. Does anybody even know what I am talking about?

Wes

 

90 psi sounds pretty high when its meant for fluid, not air.

 

Meaning I should have better results with lower pressure using fluid?

 

Well the air leak could come from using high air pressure, instead of what it was design for which you cant really do as a test.

 

You're right. And the bare minimum pressure it will have at idle in drive is 53 PSI, but that is a lot different when it comes to hydraulic pressure. I will check it out one more time but I am pretty sure it will be ok. Thanks man.

 

it's the same principle as when you do a dry/wet compression test on an engine. The dry test will always yield lower pressure than the wet test because the oil seals up tiny holes that air is able to pass through when dry.