Installed larger tires.
2007-08-05 14:04:57 · 5 answers · asked by gejandsons 5 in Cars & Transportation ➔ Car Makes ➔ GMC
You will have to replace the driven gear on the speedo output at the trans. This simply pulls out after removing the retaining bolt. Usually there are four or five choices depending on options. You will have to do a few calculations before deciding which one is right.
2007-08-06 10:07:08 · answer #1 · answered by Deano 7 · 0⤊ 0⤋
The speedo drive gear that's in the fitting where the cable attaches down by the trans has to be swapped out for one with less or more teeth depending on how off the speedo is---generally, 1 tooth equals 5 mph at 60 mph, so if it's reading 65 at an actual 60, you need a gear with 1 more tooth and if it's reading 55 at an actual 60, you need 1 less tooth and so on. Dealership parts dept will have an assortment of different gears or you may have to have a speedo repair shop build a reducer to go in between the speedo cable and trans fitting.
2007-08-05 21:17:53 · answer #2 · answered by paul h 7 · 0⤊ 0⤋
Check out Superlifts web site, they make a module for this, assuming it is computer controlled, if it isn't than you are looking at changing a speedo drive gear, most likely located in the t-case.
unless you end up changing the ring and pinion I wouldn't worry about it to much.
2007-08-05 22:29:54 · answer #3 · answered by Anonymous · 0⤊ 0⤋
i have my truck which is 89 GMC S15 jimmy and my rear tires is 30x10.5/75/15 it pretty big tires and it was very close to the fender with my 2 finger between them.. the speedometer r fine to me..
2007-08-06 02:55:32 · answer #4 · answered by One happy mommy 2 · 0⤊ 0⤋
get a programmer it has the setting for smller and larger tire best option becuase you can get performane with the same progammer
2007-08-05 22:58:32 · answer #5 · answered by Anonymous · 1⤊ 0⤋