I recently purchased a replacement gauge cluster for my '84 Z cause some of the needles were broken off of the old one. Everything seems to work properly except that the tach reads really low as compared to the old one. I believe that the old one may have come from a car with a 6 cyl. instead of a 8. Can anyone tell me, if I transplant that little yellow box from the back of the old cluster onto the replacement, will that cause my tach to read as it should? If not, how can I correct the problem?
Thanks in advance.

 

If you use a 6 cyl tach to read the rpm of an 8 cyl engine, the tach will actually read 25% higher ratio than the actual engine rpm. Sounds like your tach needle may need to be repositioned, if the tach error is a fixed value & not a ratio.

Tim