1996 Lexus SC 300 A340E fine when cold, major problems when

Tiny
BADBOBBAD
  • MEMBER
  • 1996 LEXUS SC 300
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 210,000 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?
Tuesday, February 24th, 2009 AT 5:29 PM

3 Replies

Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
Hi badbobbad,

Thank you for the donation.

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


https://www.2carpros.com/forum/automotive_pictures/192750_ManualShiftTest96LexusSC300_1.jpg

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Wednesday, February 25th, 2009 AT 9:40 AM
Tiny
BADBOBBAD
  • MEMBER
  • 6 POSTS
Please re-read my question. I have already done the manual test. Any other suggestions?

Thanks, Bob
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Wednesday, February 25th, 2009 AT 11:51 AM
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
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.
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Thursday, February 26th, 2009 AT 7:43 AM

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