C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

85 transmission problem

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Old Aug 2, 2017 | 05:54 PM
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Rocky Brian Lamb's Avatar
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Default 85 transmission problem

Does anyone know why my transmission jumps in overdive fast. It will go in at low speed. Thanks a bunch
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Old Aug 2, 2017 | 06:03 PM
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Automatic or manual? And at what speed and RPM?
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Old Aug 2, 2017 | 06:29 PM
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Automatic. 35-40
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Old Aug 2, 2017 | 06:39 PM
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TV cable adjusted properly?
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Old Aug 2, 2017 | 06:46 PM
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Yes
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Old Aug 2, 2017 | 07:30 PM
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You sure you are feeling 4th and not lockup? Mine will lock in third.
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Old Aug 2, 2017 | 08:08 PM
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Early 85 ECM was programmed to lock up at anything over 15mph. It was miserable. I got mine flashed and changed to 40 plus and it made a huge difference. Pull the EPROM and see what program you have. The .bin file can be found online.
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Old Aug 2, 2017 | 08:41 PM
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It is like if driving a manual 2nd to 4th. It if you driving normal. If you go kinda fast when pulling out it don't do. I have just shifting in o.d. when I get up to speed.
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Old Aug 2, 2017 | 10:10 PM
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Mine will lock at 42 in 2,3,OD, or if you floor it at any speed. My take on it is the TPI sensor locks the transmission on its own past 1/2 throttle. That is what I read somewhere.
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Old Aug 3, 2017 | 02:56 AM
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These are the conditions for torque converter lockup on my car:

Vehicle speed > 40 MPH (it actually locks at 42 MPH on the speedometer)
Coolant temperature > 122°F

It will lock the TCC in any gear. I tested it for 1, 2 and 3.
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Old Aug 6, 2017 | 06:50 AM
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Originally Posted by Silver85
Early 85 ECM was programmed to lock up at anything over 15mph. It was miserable. I got mine flashed and changed to 40 plus and it made a huge difference. Pull the EPROM and see what program you have. The .bin file can be found online.


The early ecm had this issue there was a recall to change this after a lot of complaints, you can replace the eprom with a performance one that has the lock up at higher RPM.

See below and read the changes, is probably the easiest option.

http://www.parts123.com/corvettecent...050f&ukey=6056

http://www.parts123.com/corvettecent...050f&ukey=6053
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