I own an 84 Z28 with the unattractive 85MPH dual needle speedo.....I bought an IROC [don't know what year] 145MPH speedo and I installed it and I am running into some trouble. First the tach was way off....it said I was idling at 2K RPMs when it should've been 700 RPMs. I put the old tach from the dual needle cluster on the 145MPH cluster and that is fixed....but it looks different than the others. Also the speedometer doesn't work. I know when I removed the dual needle cluster there is that clip on the back that you have to hit to remove the speedo cable from the cluster. Well with this new cluster I just can't seem to to get the speedo to work with the cable....I can't get the clip to lock for some reason. Does anyone have any advice on my tach and speedometer problems? Thanks...

 

At_Rick

What you need to push the speedometer cable in and it should lock itself into place. Ensure that the clip is on the back of the cluster as you get under the dash. I have installed several and have yet to have the same problem with the sppedo. Now the tach is a different animal if the cluster was from a 6 cylinder its going to be off a few thousands. Just switch you old one in the 145 cluster.

 

Is there anyway that I could exchange the faceplates/needles on the tachs of the two clusters but keep my older circuit board? I know that under that needle there is a little coil type thing [at least on the speedo needle there is that coil...I'm guessing it's on the other gauges as well] and that if the coil gets messed up I'm screwed. Is it the coil of the V6 that throws off the tach or is it the actual circuit board? And if so can I do the exchange of faceplates/needles since the older tach looks a little different? Thanks again...

 

You should have been able to install the speedo into your old cluster without changing anything else. It just bolts in. It's often difficult to get the inner cable into the square drive on the speedo. Remove the trans end and have a friend spin the cable while you try to get the cluster installed.

 

I have done the same thing with my 84 Z28.Although the speedo did lock into place and it has every time i've taken the dash in and out of the car.The only other problem you are going to run into(well this is what happened to me) is that your speedo is going to be off a few mp/h while your driving.Mine is in KM/H(i'm canadian) and when i'm traveling at the speed limit out in the country(80km/h) my speedo reads at around the 100 mark.I have to change the speedo drive gear to read properly with it.

 

They are calibrated the same.

 

As far as i knew the drive gear in the tranny was different with the different speedometer's.Hum then if they are calibrated the same mine is just way off