Speedo flutters when temp is hot - LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums
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post #1 of 3 (permalink) Old 07-21-2013, 01:41 PM Thread Starter
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Speedo flutters when temp is hot

I'm helping my father work on my brother's 98 camaro with 3.8 engine. We recently changed the motor, due to the original having a cracked block. Everything works great, motor runs smooth, tranny shifts smooth. Only issue we are having is with the speedo when the outside temp is above say 80 degrees. No matter if the car is cold or warm it does this. It seems to be happening while turning to the right or even cornering to the right. He said it has even happened once or twice while driving straight.

The speedo will drop in steps and the rpm gauge will jump way up as if the tranny is slipping. He said it felt like the tranny didn't want to shift when it does this. My brother posted a youtube video to show how it is acting and I will try to post the link.... https://www.youtube.com/watch?v=3UsCzkfJ4HA

The video shows and tells what the car is doing. Any help with this issue would be greatly appreciated. Oh and we have replaced the speed sensor in the tranny twice, and traced the wires back looking for bad spots. Going to ohm out the wires also to check for breaks or short to ground.
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post #2 of 3 (permalink) Old 07-22-2013, 01:00 PM Thread Starter
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My father was looking everything over again and tracing the wires that go to the tranny. He noticed that when he moved the wire harness that goes down to the trans. the dipstick tube dropped in another half inch. So far so good, no issues! Only thing I can think is the tube as allowing air to be pulled into the trans? Not sure but everything seems good for now!
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post #3 of 3 (permalink) Old 07-22-2013, 05:54 PM
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Hook car up to an obd2 scanner that will show running sensor data. look up the speed reading on the sensor list. See how it compares to what the speedometer is reading.

If pcm speed reading and speedometer speed reading are the same, your problem lies with the vss, or the wiring to the pcm.

If pcm speed reading is correct and speedometer speed reading is messing up, then problem lies with speedometer itself, or wiring from pcm.
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