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View Full Version : SPEEDO GEAR ADJUST


ERIC
04-03-2000, 03:02 PM
THIS MIGHT BE A STUPID QUESTION? I OWN A 1979 CHEVY 4X4 PICKUP WITH A TURBO 400 TRANSMISSION, 40" TIRES, AND 4.10 RUNNUNG GEARS. THE PROBLEM IS WITH THIS SIZE OF TIRES MY SPEEDOMETER IS WAY WAY OUT OF WACK. I KNOW THEY MAKE SOMETHING TO ADJUST THE SPEEDO GEAR RATIO BUT I HAVE NO IDEA WHERE TO FIND THIS ITEM. ANY INFO WOULD BE GREATLY APPRECIATED. THANKS

Doug406
04-04-2000, 12:28 AM
Your chevrolet dealership. They will have a bunch of different gears for you. what you must figure out is which one. On a 79 you should have a 203 case, there should be a little converter box where the cable goes in the case. Try removing that all together and see what your speedo says, otherwise swap gears (about 7 bucks a pop). There is a mathmatical way of figuring it out, but i can not remember it. Something like old number of teeth on speedo gears / old tire size x uknown new teeth needed/new tire size. Example 32teeth/29" tires times T(unknown)/40" tires. That may be it.

mpastor
04-11-2000, 01:45 AM
The other thing you could try would be to go to a Speedo calibration shop. They could calibrate your speedo to compensate for the larger tire/wheel size.