Hey guys, yes, I did a search on this and turned up nothing. First of all let me tell you what happend today- I was driving at around 45 mph and everything is fine, the second I hit 50 mph, my guage goes crazy (speedo.) Also, I notice a buzzing noise coming from the enge compartment, right in front of me. I am thinking it was one of the relays mounted to the firewall, next to the brake booster. So after I hit the red light, I tried it again, at 50 mph, same thing happend. I want to take it on the freeway to see what it does even faster.

Has anyone had this problem before? Car is an '89 IROC-Z 350. Oh yeah, are my guages electrically controlled? So if anybody can help me out here, I would appreciate it. -89IRO

 

I can't say I've ever heard of the problem but, I'll take a guess for the fun of it. Since your speedo is cable driven, the noise might be from the cable 'chattering' inside the liner (from wear over time and/or lack of lube inside). I can't say that for ceertain though but, the cable does enter the firewall around where those relays are.
If I were to check, I'd take note of what RPM 50+mph is and then unhook the speedo cable from the trans. This will most likely throw a code and also prevent the converter from locking (this won't hurt anything) but, if the noise doesn't persist, you've found the source of your problem.

 

Thanks deadbird, any more thoughts anyone? What's wierd is today when I drove home, there was nothing. I even had it at 65 (I know, I know, in a 45) and there was no needle hop and no noise. I wonder if the cold in the morning had to do with it. Or maybe it is just slowly giving out and that was just a warning. Are all of my guages (speedo, rpm, temp, batt., fuel, and oil) ran off of a cable, or just the speedo? I thought all the later 3rd gens had electrical guages. I'll drive to school tomorrow morning and see what happens then I'll let you know. -89IRO

 

I have the exact same problem with my 89 IROC 350. Normally I just turn the radio up loud enough to cover the sound of the speedo cable chirping. I haven;t gotten around to fixing it, but it is definately your speedo cable. Easiest thing to do is to re-lube it. Should get rid of your problems. A good lithium grease should do the trick.

 

if the car is an 89 it should be electronic, mine is and its an 86. the speedo is the only thing with any chance of being cable driven everything else should be electric. the easiest way to check is at the firewall or on the tranny.

 

Tim, 89 is talking about a Camaro (89 Iroc), they were still cable driven up to 89, 90 they went electric. Firebirds went electric a few years sooner.

 

O.K., so how exactyly would I grease this cable? The speedo cable is the one going to the tranny right? And for all of my other guages, are they cable or electric driven? Thanks guys! -89IRO