1996 Lexus SC 300

Transmission problem
1996 Lexus SC 300 6 cyl Two Wheel Drive Automatic 210000 miles

Removed valve body for a complete fluid drain. Top & bottom valve body gaskets shot. Opened up valve body to replace gaskets. Used a 1990 Supra A340E diagram for procedures, rubber balls, colored springs, etc. Reinstalled valve body. Works fine when cold, however, major slip in reverse & no upshift from 1st to 2nd, etc. When at operating temp. Disconnected solenoid harness to test manual operation - same problem. Removed valve body & ran compressed air thru ports to check operation of reverse, 1st, 2nd, 3rd, O/D, etc. - All sounded as they should. What to do, what to do? Valve body problem? Why fine when cold but not when warm?
February 24, 2009.

Hi badbobbad,

Thank you for the donation.

Do a manual test to confirm if it is mechanical or control fault.

Feb 25, 2009.
Please re-read my question. I have already done the manual test. Any other suggestions?

Thanks, Bob

Feb 25, 2009.
Hi Bob,

I would like to apologise for the oversight on my part regarding the manual test done.

The manual test confirms that it is a mechanical fault and possible causes are : Reverse gear slipping.
Faulty 2nd coast brake, front and rear planetary gear unit or direct clutch.
Faulty 1st and reverse brake.
Faulty OD direct clutch.

No upshifting.
Faulty 2nd brake or No. 1 one-way clutch.
Faulty direct clutch.
Faulty OD brake.

Since problem arises only at operating temperature, it could be caused by one or more seals that loses their sealing properties and resuting in loss of line pressure.

Valvebody problems should be more consistent and not only when at operating temperature.

Feb 26, 2009.