tim bob

on my 76 ever since i bought it the speedo it doesnt bounce its just runs slow i was going to purchase a new cable but i notice theres either a one piece or a two piece cable how would i know which one is on my car?? also i see the 45 degree adaptors are they worth installing on my car thanks tim bob

fanmanbd

If it's just reading lower then your true speed you need a smaller driven gear.

Mark Riles

The two piece cables are for cars with cruise control. If you have cruise you have two cables. It's possible the slow reading is from the cable dragging inside the sheath which may be dry and it's binding slightly. More than likely though as mentioned above it's because someone put on a wheel and tire package that is not stock and the diameter difference is affecting the speed your speedometer shows. Can you post the tire size?

Mooser

I've never seen a 45 degree adapter, did you mean the 90 degree ones? Although I guess it would fit normally they are for the tach-drive distributors where the cable has to take a real sharp bend against the firewall. Don't recall anyone needing one on the speedo.

If you want to see if it's a two piece cable (auto only I believe) have a look underneath, you will see a joint in the cable about 6" or so up from the bottom of the firewall

Again, if it's just running slow compared to your speed, (proportional, like 10 mph slow) you need a new gear
Mooser

Vette5.5

It may be best driving along with a friend in another car while in communication, to see what percentage both your speed and odometer milage are off, before playing with speedometer gears.

tim bob

i will post tire size tomarrow i did remove my one piece cable looked great thanks tim bob

tim bob

ok my tire size is p225/70/r15 car has stock rally rims thanks

mcmsmsc

had problems with the speedo in my 77. it was bouncing then it quit working except for the ocassional bounce from 0. turns out it was in the cruise control. my mechanic is a vette owner and knew what the problem was right away. i can ask him what he replaced if you would like.

tim bob

my speedo doesnt bounce its slow moving and not the correct speed. i dont have cruise control but thanks

drwet

Get a GPS. And I agree, you need to change the sppedo gear in the transmission. Once you know how far you're out, and how many teeth are on the gear you have, some simple math will tell you what gear you need. Simple fix.

7t9l82

well, mines really wired. at 20 indicated it is doing 32 according to g.p.s and at 70 indicated it's. doing 70. any thoughts on that?

tim bob

i will put car back together and get a gps and see what the differance is in speed i wonder why it would have changed ill order a new cable instead of putting old one back on it will take me alittle while to reassemble car but will post results in what i find. if anyone else has any ideas please pass them on thanks everybody tim bob