Speedometer, tach and digital clock questions
 

t’s a 1980 none turbo with a 5 speed, the 80 mpg speedo and the quartz clock.

My speed is off between 10-20 mph depending on the speed I’m traveling, and the needle “jumps” all the time . I have checked the cable from the tranny to the pigtail under the dash, that cable is fine. To get to the pigtail and the back of the speedo, will I have to remove the dash, or how do I get to it? (my Haynes has not arrived yet)

My tach works about 90% of the time, but it has been known to not moved at all. How can I be sure it is working correctly, and not acting like the speedo?

And for my daughter. My digital clock does not stay on. At times it works fine, and she sets the time, then the clock will lose all power for some reason. It drivers her crazy, and I don’t need a crazy 15 year old bugging me to fix the clock. Any suggestions on this one?

Thanks for your help

There are two reasons for the speedo jump:
-kink or bend in the cable
-the actual inner metal cable that spins is rubbing on it's outer jacket and that needs to be greased.

Since you have verified that there are no kinks, I suggest pulling the cable from the car, slide out the metal wire that spins, clean it, grease it, and re-install.

You can also pull the cluster w/o removing the dash, but since you have other electrical probs, you might as well pull the dash.

You can also download the FSM for free at www.xenons130.com/reference

sorry, I should have been clearer.
I did pull and re-greased the cable. its not as bad, but still does not stay still.
How much grease should I use. just keep at it until it not longer jumps, or is there a point when I can over grease it?

A dash pull is planned, but its winter in Arkansas, and a little to cold to work outside for that long

Hum... it was 17*F the other night when I changed my oil. :D

I have a low mileage speedometer out of a 80 model 280zx. Its the 85mph speedo w/ 26k on it. If you want it, i'll sell it for $35 shipped. E-mail me @ sk84life1122@sbcglobal.net if interested

a little update
 

I pulled the (sorry can not remember the term)cog the speedometer cable connects to. Its "white", but it does show some signs of wear.

From what I have read, white is the color that should be in my car based on the year.

Will the wear on the cog explain the speed being off, or do I have the incorrect color cog?

If its the cog, how do I find the correct color for my car?

There's no white cog... maybe the orange-tan one?

Before you go chasing a ghost, have you verified that the cable spins smoothly from one end to the other? Have you verified that your speedo actually reads when you spin it by hand?

You forgot the 21 tooth Purple... the one I'm looking for my 4.38

have you not driven the car for awhile? when i first got my 1972 van after sitting for about 2 years the speedometer would jump like crazy, but the more i drove it the more it smoothed out

Actually there is a white one for the 3.9 rear end....... maybe these are for the Roadster 5sp?

https://www.zdriver.com/forums/attac...1&d=1327905040

even more confused.
 

Now Im really confused. :102:

The cog is white, so that makes me question what tranny and rear end I have.

How do i find out what gear ratio I have so I can get the correct cog?

I have put about 2000 miles on in the last month (my DD), and the speedo still jumps.
At this point, Im just going to replace the cog, if I can figure out what the correct one is.

ps. yes the cable turns on both ends. and the speedo with move if its connected and i turn the other end my hand.

Hum... interesting. :D That pic is of the 4 main 280Z / 280ZX cogs. I'm sure there are plenty of others made by Datsun / Nissan.

Post a pic and count the teeth of your white one... then we'll know exactly which one it is. :023:

I know what I have, I dont think it is correct.

How do i find out what is the correct cog to use.

My speed is off, and depending on the speed, its not the same. if the speedo is at 30, im doing 40 mph, but when it reads 70, im doing 85.

Ghost! =) all three I've owned clocks didn't work at all two had flappy spedo's my current t top well the dome light switch makes the door light come on..............30 year old wireing my friend =) do your self and kiddy a favor go down to target buy a 90.00 garmin that displays speed and time as well as directions. . . . My wife got a theft recovered 86 corvette with a bad digi dash . . . . After a few tickets and points we did that solved the problem. . . . Try telling the cop you were doing 80 in a 65 while driveing a sports car because you can't tell how fast your going :)

I'm having similar troubles in my '81. could a similar problem cause my speedo to read erratically any time i'm under 30 MPH and cease to operate/ get stuck at 70 MPH? If i slow down from 70, it freezes, and takes like a minute for it to swing back down....

I'll take it out and grease it.

Hey thanks for bumping this thread - I forgot I need to order that cog lol