Speedo Calibration?

[samotahoe]

Ive recently lifted my 2000 tahoe 2wd with 5.3L. i only used the 3" spacers on the rear and torsion keys for the front. went with some 315/75/16 wheels and tires and now i was wandering if there is a way to calibrate the speedo to the new set up. i was on the highway last night and my speedo said was doin 65mph but when i went passed a radar thing on the side of the road that tells you how fast you are going, it said i ws doing 72mph. i know thats a big difference. If anyone has any info on this procedure or the type of shop that would do this besides the dealer that would be appreciated. and i live in southern california so speeding tickets are my enemy cause highway patrol is always looking for giving out tickets.

 

[Kunihiro]

I know your in San Diego, but there's a shop in Pomona, CA, called "The Toy Shop." It's a little out of your way, but they only work on GM stuff and years ago, the shop was featured in Super Chevy magazine for their performance work on tranny's and rear ends.

I take my '69 Camaro there when I need that type of work done.

However, I'm sure there are many other available shops in your area that can help you with your problem.

I'm not up on all these new computer based vehicles, but on the older cars, it was a matter of calculating tire size, rear end gear ratio and then changing the speedo gear in the transmission. The newer stuff is all greek to me.

Here's a link for speedo calibration:

http://www.csgnetwork.com/speedocalibcalc.html

 

[samotahoe]

Hey thanks for the info, greatly appreciated. I will look into it more but it seems like IM going to be stick with the situation I've spoken with a few people and seems like only fixin to this problem is re gearing my diff, but I recently rebuilt it so IM not looking to do that again.

 

[samotahoe]

so i found out what needs to be done... the truck needs a PROM update. only way to do that is to either have the dealer or a shop that is well equipped with the software to do so. all they have to do is input the size tires, etc and the truck will calibrate accordingly. this also effects shift time and the rpm at certain load because i was having that problem before and now its gone.... just some info for those that are looking and need to do so as i did.