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.
correct speedo ratio
Apr 05, 2005
4 Replies
You will need to recalibrate your DRAC. See:
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Rita
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
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.
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.
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