Speedo fault

[yoshi]

Anyone had problems with mechanical Dolphin speedo not working properly? Got mine hooked up to TH350 & won't go above 20mph

[Wrenchbender Ret]

Ive never used a Dolphin gauge but if the cable core is to long it can cause a problem like that.

[Mattyparty]

Did u program your speedo?

[yoshi]

Program it?

[tmoble]

mechanical, no programming. That I know of anyway.

[yoshi]

That's what I was thinking, I called Dolphin & they said I need a speedo healer. Each time I go out in the truck it increases

[mr48chev]

There should be shops in the UK that test and calibrate speedometers and I'd think it would be a minimum cost to have one test the speedometer to see if it is functioning correctly or not functioning correctly.

If the problem is in the drive gears in the trans check this site for info on how to calibrate the drive gears http://www.transmissioncenter.net/sp...n_______va.htm You will have to find the right gears for your transmission on the list as the page covers a big number of vehicles and brands.


You may be able to source the correct gears locally or get a ratio adapter locally that has the correct gears in it to correct your speedometer. Those are often used here by the four wheel drive people who are always swapping tire sizes.

[Apachemike]

Remove the cable from the trans and check with a variable speed drill. It will help narrow down the source some

[Mattyparty]

I would look at your instructions. On mine it said to take the speedo apart and there are pin switches. I googled it and found this link. Read this

http://www.alanhorvath.com/54chevy/dolphingauges.php

[yoshi]

That link is for electronic speedo

[_Ogre]

Remove the cable from the trans and check with a variable speed drill. It will help narrow down the source some

that will tell you if the speedo is calibrated right, most american cable driven speedo's are calibrated at 1000 rpm
it will also tell you if you have a problem in the cable drive; as in the cable slipping in the trans

if the speedo comes apart easily look for the needle hitting either the face or the back
i know with the mods i did on my stock speedo i had to bend the needle carefully to go between the face and volt meter

[yoshi]

I put a drill on the gearbox end of my new cable & it went up to 50mph

[_Ogre]

that proves the costly speedo is good, that is a plus

sounds like you have a cable drive problem
you should not be able to turn the speedo cable from the top
possible solutions:
gears are worn so much they're slipping at speed
cable too short, not fully engaged in the drive gear
end worn in driven gear allowing the cable to slip

you should not be able to turn the speedo cable from the top
if you feel a click and it turns check the drive parts

since you have the cable loose from the bottom
try using a square drive screw driver in the driven gear to see if it spins

[yoshi]

Speedo suddenly stopped working so I had to do something about it. I removed the gearbox end & the worm seemed good, I discovered that the inner cable was going too far into the worm. I put a small piece of metal about 1/8" into the hole then pushed the inner cable back in. All seems fine now

[mr48chev]

The inner cable may be cut just a bit short but if that took care of it life is good.


The best way I have found to figure out how accurate or not so accurate a speedometer is is to use a handheld GPS and drive at a set speed and calculate the percentage of difference and which way it is off and go from there.