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Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 4410
Experience:  ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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I have a 93 silverado 1500 standard. my speedometer is

Customer Question

JA: Thanks. Can you give me any more details about your issue?
Customer: I have a 93 silverado 1500 standard. my speedometer is lagging. it is saying I am going much faster then I am really going. what can cause that
JA: OK got it. Last thing — Chevy Mechanics generally expect a deposit of about $18 to help with your type of question (you only pay if satisfied). Now I'm going to take you to a page to place a secure deposit with JustAnswer. Don't worry, this chat is saved. After that, we will finish helping you.
Submitted: 7 months ago.
Category: Chevy
Expert:  Jerry Newton replied 7 months ago.

Tire size is obviously a factor. If the tire size is correct, then there is something wrong with the DRAC (digital ratio adapter card). This little device translates the speedo information from the vehicle speed sensor, and it compensates for tire size, gear ratio, etc. and sends the signal out to the speedo.

You'll have to visit your dealer to get one of these ordered, it sounds like perhaps someone changed the DRAC at some point. It's common when people change gear ratio or tire size, and they want to correct the speedo reading. The DRAC is the device that takes all of these things into account, so you'll need to know tire size and gear ratio when you go to your dealer to order one.

Customer: replied 7 months ago.
I have the correct size tires
Expert:  Jerry Newton replied 7 months ago.
Any chance that the axle ratio has been changed from stock? There is also a good possibility that someone installed a junkyard drac into this truck that was programmed for a different vehicle.