correct speedo ratio

1990 chevy-1/2,PU, 2wd,700R Tranny, I am going to change my stock diff ratio from 3:08 to 3:73. What ratio will I need for the speedo drive and is it a problem to change that ratio at the tranny? The speedo is
correct with stock 3:08's and the current tire size.
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You will need to recalibrate your DRAC. See:
http://614streets.com/drac.html
Rita
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Rita Berkowitz wrote:

diff
drive
is
Thank you, but do they us this system on the 1990 models, as far as I know the computer does not control the tranny but could be wrong
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On 5 Apr 2005 20:03:25 -0700, snipped-for-privacy@yahoo.ca wrote:

I don';t know specifically about your vehicle but I discovered that on my 89 S-10 there was no speedo cable and it appeared that the speedo and tranny were getting their speed signals from some kind of electronic system. I was not aware of this DRAC thing when I was looking at recalibrating my speedo (I gave up). Now I'm going to go look for a DRAC module somewhere. If it's on the ECU I may try playing with it. If it's on the back of the IP I'll probably just leave it be.
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Your DRAC is attached to the computer behind th glove box. Don't buy a DRAC from a dealer, their part numbers are wrong. Go to this site and follow the links and you should be able to modify your system for no cost.
http://www.philter.com:81/cgi-bin/drac.pl
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