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Re: [GMCnet] Reviving the Cad 500 [message #164829 is a reply to message #164811] Sat, 31 March 2012 20:11 Go to previous messageGo to previous message
shawnee is currently offline  shawnee   United States
Messages: 422
Registered: February 2004
Location: NC
Karma:
Senior Member
Ken Henderson wrote on Sat, 31 March 2012 19:06

Really great day today -- NOT!!!

Yesterday and this morning I connected pressure gauges at the torque
converter output, in the return from the ATF filter (which follows the
in-radiator cooler), and in the diagnostic port.

This afternoon, Stick and I ran all of the pressure tests on page 7-13 of
the X7525 manual. The results were pretty well centered in the normal
range except for those in Super and Low range, which were low. Disrupting
Manny's Saturday rain-watching, I called him for consultation. He says
those low readings indicate a leaking accumulator, which I can live with --
it's not relevant to the current
The pressure readings on the cooler circuit were pretty much in the range
of 20-30 psi, with the return only 3-5 psi lower than the supply. The
highest converter output pressure recorded was 40 psi, with 30 psi return
-- probably a reading anomaly. Those are all "open circuit" measurements.
To test the condition of the TH-425's pressure regulator, and the
potential damage from a blocked cooler, I blocked flow in the circuit by
clamping a rubber hose. We than ran with the transmission in Drive and the
engine at 1000, 1500, and 2000 rpm. The corresponding pressures were 80,
100, and 100 psi -- close to Manny's predictions.

The highest reading we recorded anywhere was 160 psi at the diagnostic port
at 1000 rpm in Reverse. I suspect that was a false reading, because none
of the other readings, all of which were repeated at least 3 times, was
above 122 psi.

So, it appears that the transmission is NOT responsible for my thrust
bearing failures. While we have no way to directly test the pressure in
the converter, the output pressure should be pretty close. And as shown by
the blocked cooling circuit measurements, that pressure should never be
above 100 psi. While having that much pressure continuously could over
stress the thrust bearing, the un-blocked 20-25 psi would not.

Manny and I discussed a number of different possibilities without forming
any new hypothesis.

I'm completely baffled and directionless right now.

Ken H.

Ken,

When you had the first failure, did you clean the oil cooler out real well? If you didn't, then the stuff in the oil filter could have come from there. I haven't been able to follow the net at Shawnee due to poor WiFi so I am sure you have done more.


_______________________________________________





Gene Dotson
74 Canyonlands
www.bdub.net/Motorhome_Enhancements New Windows and Aluminum Radiators
 
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