not really sure where to post this, but as it is a general question...


I just brought home my new '87 Iroc yesterday, but the speedo is messed up. I was driving behind a friend, and when my speedo read 60mph, we were really going 70mph. Anybody know how to adjust it? I don't know if my year is electronic or cable-driven. I also gotta put in new gauges as the old one is in km thanks for the help

 

It's electric. There's a VSS (Vehicle SPeed Sensor) in the tailshaft of the tranny that connects to the ECM, which in turn runs the speedo/odo.

How to adjust: not sure. I believe that year had a set of gears on the VSS itself, but if they can be changed to different gears to alter the speed reading I have no idea.

 

What size of tires does it have on it. Do you know if the rear end is original? These are a few things that can affect speedometer readings. I have an 87 firebird and the speedo is electric. As far as adjusting, there are different sized gears for the sending unit in the tranny.

edit- drives me nuts when other people reply when you are typing your reply, makes a person look like a me too, what he said type of guy. lol

 

I have an 87 IROC and I'm sure mine is cable driven. Mine also read low (about 25%) and the cause is down to, I believe, the wrong speedo gears. Either the rear end gear has been changed or the tranny was swapped out and the person who did it didn't change the gears-that's what my situation is.

 

my car still has the original tranny, and i dont know why the speedo gears would ever have been switched out. my rear end is original, and my tires are 245/50R/16 (don't know if that's stock size or not).

 

an 87 IROC will be cable.....I belive IROCs (all camaroos) were cable until 89/90 and firebirds were cable until 86/87(?)

sounds like you may need to change your speedo gears(in the trans), the gears or the rear end may have been replaced

 

my 84 has all oem and it has a vss for the spedo no cable

 

Check your door jamb for the factory size tire and compare that diameter with the diameter of the tires you have now.
245/50R/16 is a 25.6" tire, if the factory tire was signifigantly taller or shorter that could explain it.
My factory tire was a 215/65 r15 and was a 26'' tire.

 

what car do you have? does it have a digital cluster?

 

yup and it works after taking 2 to make one