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We installed a 1994 used transmission into a.

Tiny
MONT.AUTO
  • MEMBER
  • 1995 LEXUS SC 400
  • 150,000 MILES
We installed a 1994 used transmission into a sc400. Only issue originally was a hard shift when putting directly into drive but, if you would first put selector into reverse and then into drive, no hard shift. Recently, had the transmission flushed.
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Friday, November 18th, 2011 AT 5:57 AM

8 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Is the transmission the same type as the OEM?
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Friday, November 18th, 2011 AT 5:59 AM
Tiny
MONT.AUTO
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  • 32 POSTS
Yes. Only difference is that it came from a 1994 Lexus SC400
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Friday, November 18th, 2011 AT 6:43 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
My concern is there is a difference in sensors or shift solenoids and the computer can not communicate properly with it.
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Friday, November 18th, 2011 AT 6:48 AM
Tiny
KHLOW2008
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  • 41,814 POSTS
Have you checked for trouble codes?
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Friday, November 18th, 2011 AT 1:04 PM
Tiny
MONT.AUTO
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  • 32 POSTS
Good question. My impression is that if the computer was the problem, the issue would be more consistent; meaning, why would the difficulty with the transmission shifting automatically only occur after the car hasn't been driven for a couple of days and resolve itself shortly after being engaged. Also, why did the shifting issue only occur after the flushing process. Lastly, what changed between the 1994 and 1995 models? Have a good day.
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Friday, November 18th, 2011 AT 5:53 PM
Tiny
KHLOW2008
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Our database indicates that there are no changes between 94 and 95 models.

From the symptoms described, the most common cause for such faults lies with the valve body, usually related to the solenoids.

There are manufacturers that strongly advises against flushing transmission because it can create problems when debris are stirred from somewhere to be lodged into orifices causing shifting problems.

If there is a problem with the solenoids etc, the trouble codes would tell you which is not working correctly. Some solenoids might stick and work itself free after some running.

Such causes would not be consistent.
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Saturday, November 19th, 2011 AT 3:48 PM
Tiny
MONT.AUTO
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If the debris is chemical in nature, are you aware of any solvent or other chemical solution which can resolve such a blockage? And, why does the blockage disappear once the unit is warm (or after the transmission is engaged for a few minutes)?

Have a good day.
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Sunday, November 20th, 2011 AT 4:37 AM
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
Usually these are bits and pieces of metal filings or clutches and there are no chemical that would clear them.

It might not be blocked orifices that is causing the problem. It could be stuck valves or solenoids that worked themselves free after warming up.

Under such circumstances, your best bet would to have the valve body removed and serviced if there are no trouble codes.
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Sunday, November 20th, 2011 AT 4:51 AM

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