Speedometer / Fuel Gauge Question

[elcaminodude]

I have 2 issues with my 79 El Camino. My speedometer needle is sitting on 5 mph with the car sitting still. The error in speed increases as the speed increases. It gets up to 15 mph difference with the gauge showing 15 mph faster than I am actually going. Any ideas on what could be the cause?

Also, my fuel gauge bounces erratically and never really shows how much gas I have. Does this sound like an issue with the sending unit or the gauge? Any help on either or both issues would be greatly appreciated. Thanks!

 

[Gordo_AZ]

Check the speedometer cable, first on the dash and follow it to the side of the transmission. There is a plastic ring type deal in the spedo assembly, make sure it doesn't spin, the cable should go in tight. If it just spins or something doesn't look right, or you see a leak might have to pull the spedo assembly out (fluid will leak, jack it up from that side) and have a pro look at it. If the cable and spedo are fine, its your gauge and if that's the case, buy a new one.

 

[JBreu]

With regards to your fuel gauge, you might possible have a bad ground. There's a ground from the tank to your rear bumper, iirc and that may be where your problem lies...

 

[elcaminodude]

Cool. Thanks y'all. I will check both things and let y'all know how it turns out.

 

[beermonkey9417]

i had a problem with my fuel guage and par of it was i took the cluster out and the lil tabs on the printed circuit were bent over on eachother and that caused a weird short. and like the other guy said is check yer cable. a question i have for you also is have you changed out the rear end gears or swapped rear ends, or did you do a trans swap?

 

[elcaminodude]

I haven't changed the gears or rear end, but I just bought the car in April and it had a new engine in it, not sure about the transmission or rear end. I still haven't had a chance to check it out. The confusing thing about the speedometer is that it is sitting a 5 mph when sitting still. Can that be reset?