Speedometer Way Off
#1
Teching In
Thread Starter
Join Date: Feb 2011
Location: Griffin, Ga
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
Speedometer Way Off
I bought a 98 z28 but noticed the speedo is way off.. At 60mph (speedo) actually 45mph @ 1500 rpm... Does this seem to be a gear a change? I want to get the pcm tuned but not sure of what is needed.. Any help would be appreciated..
#4
TECH Enthusiast
iTrader: (1)
You can figure out the gearing. Jack the vehicle up, turn the wheel 1 revolution, and see how many revolutions the driveshaft spins. If it's different than what the car rolled of the factory with, that could be it.
As someone mentioned, improper tire size can also throw off a speedo.
As someone mentioned, improper tire size can also throw off a speedo.
Trending Topics
#8
Don't throw a VSS at the car without measuring your gear ratio which is in all likeliness what is causing your inaccurate cluster reading. VSS failures will typically (and i Do mean 99 percent of the time) cause the speedo to either be inoperable altogether OR incredibly erratic (Bouncing to 140mph to 0 to 75 etc). You WOULD also get a VSS code.
I'm constantly amazed by the "Throw parts at it" mentality so commonly found online. In no way shape or form would throwing a VSS at the car make the list of the first 5 things any GM tech would even do to diagnose this problem.
I'm constantly amazed by the "Throw parts at it" mentality so commonly found online. In no way shape or form would throwing a VSS at the car make the list of the first 5 things any GM tech would even do to diagnose this problem.