Tach reads 2500-3000 at idle.... Trans shifts too soon.

[2RARE84s]

Ok, so my T/A has an issue with shifting that I thnik is due to a sensor or something. The tachometer reads 2500-3000 at idle... It's not actually idleing that high, it sounds to be idleing at 900 or so. I think whatever is causeing the tach to read so high is causing my transmission to shift too soon. I believe it is a 700R4. The only sensor I find that I think it could be is the "Vehicle Speed Sensor", but I'm not sure if that would effect the way the tach reads the RPMs. What else could it be?

[V]

afaik, an 84 should not have a VSS, The birds first got them in 85, camaros in 90.
an improper signal from the tach to the ecm MAY be causing the shifting issue. i'd try to get a cheap spare tach and run it off the coil/dizzy to see exactly what the motor is doing and go from there.

[2RARE84s]

i'd try to get a cheap spare tach and run it off the coil/dizzy to see exactly what the motor is doing and go from there.

Sounds good, I can try that. Thanks!

[JSPERFORMANCE]

The tach signal will not affect a 700r4 the only function the ecm has over the trans is the lock up. Your problems are most likely not related.

[2RARE84s]

Hmmm.... interesting. Will have to investigate further.