Shift Point?

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May 19, 2011 | 05:08 PM
  #1  
What does everyones 3.1L auto shift at??? Mines shifts high...Like 6250 rpm and really makes me think that its not shifting when its suppose to....any advice... this car does run 16.70's in the quarter mile with its mods.. but worries me because of the high rpms... thanks!!
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May 19, 2011 | 08:41 PM
  #2  
Re: Shift Point?
Knowing you have a Camaro and it's a 1991, your tach is probably WAY off... You would easily know if the engine was pushing 6000 RPM at WOT because it would blow after a few attempts, and it would literally be screaming.
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May 19, 2011 | 08:45 PM
  #3  
Re: Shift Point?
Well how would i go about fixing this?? The tach reads normal when im idleing and when im going 55 its at about 2100rpms... I have no idea where to start!
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May 19, 2011 | 08:50 PM
  #4  
Re: Shift Point?
Yeah, the tach is off. At 55 with the 700R4 and the torque converter locked up, you should be about 1900 RPM. With those tachs, the thing is that the higher the engine speed, the more inaccurate they get. The only way to be sure if the trans is shifting properly is to hook it up to a scan tool as you go for a cruise. Even at WOT, the trans should be shifting at about 4000 RPM in 1st and lower as the gears pass. Only way to be sure the tach is inaccurate is to check with either an external tach that you know is good or again with the scan tool.
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May 19, 2011 | 08:59 PM
  #5  
Re: Shift Point?
Ok thanks a ton!! If i do find out that this thing is way off, which it sounds like it is... What is causeing it to be so off? Isn't there a little plastic gear that spins the cable to the tach?? Im not real knowlegable about the tachs in cars and how they work... Thanks again!!! Oh yea and I am assuming that if the tach isn't off, which it sounds like it is....That the problem would then be in the tranny, which I am totally clueless about.
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May 19, 2011 | 09:21 PM
  #6  
Re: Shift Point?
You've got the tach confused with the old cable operated speedometers... The tach is completely electronic, and is run off of the white wire on the ignition coil. The problem with the tachs is that they are based off of a Toshiba chip that was discontinued years ago. So, of course, Toshiba won't release any data on the chip so nobody can fix their tachs right. There are any number of guesses out there on how to fix the tach, mainly soldering in a resistor or capacitor somewhere, but only the pro shops REALLY know how to fix the tach if it goes screwy. You could the Electronics forum for an answer, but there really isn't much to be found for a V6 tach (most of the threads are for V8's).
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May 19, 2011 | 10:55 PM
  #7  
Re: Shift Point?
Allright thanks for the help!!!!!!!!
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