I've recently bought a '73 240Z and I noticed that the speedometer has been acting strangely. The needle bobs up and down constantly and doesn't really stay still. Is there a fix?

Typically, that is a binding or damaged speedo cable, if I understand your problem description correctly.

Well, to be more precise..

The speedometer reads pretty accurately. Although, due to the car vibrations and whatnot, the needle tends to bob A LOT.

But thanks for your input Arne!

As Arne said try pulling the cable, cleaning it and the tube and relubing the cable and tube the cable goes in. That bobbing is usually a slight binding in the tube which twists the cable slightly then releases.

My speedo only starts fluctuating when I get above 85 MPH. Unfortunately, that doesn't happen too often (often enough?) as I have a ride-along rev limiter; i.e., wife.

To all: If you haven't done what Arne mentioned, you should. This is one of those PM things that'll result in one less thing hopefully going wrong in the future. If you don't do it it'll break and then its another "NISSAN doesn't have them any more" deals. A small tube of graphite lube will do the trick. Best to remove the cable housing from the car so you can get an even lube end to end.

I pulled my speedo last night to install a metric one. I have 5 or 6 spares. I pulled one of the spares apart and they are pretty straight forward. Not much can go wrong inside them.

On my 73 240z that I sold last March '08, my speedomter was a bit unstable when accelerating only - ussually in 2nd or 3rd gear. It turned out while having the transmission rebuilt that the Nylon speedo gear to the cable was worm and even had a tooth missing. I think it was a white color gear with 17 teeth. Bought from the local Nissan dealer a replacement. They needed to know the transmission type and year, along with the color and tooth count of the gear to order the correct part. I had an 82/83 280zx 5sp manual transmission in the car.

This took care of the porblem when the transmission was re-installed in the car.

Many thanks..

Edited June 11, 200915 yr by moritz55

Hi Mark:

The speedo pinion gear has to be matched to the rear end ratio - if you want your speedo to indicate the correct speed.

Giving the transmission type and year to the Dealer - will help them find the part numbers in the Parts Catalogs. Nonetheless, you want to order the speedo pinion gears based on the rear end ratio you have in your Z. That means matching the number of teeth on the speedo pinion gear to the rear end ratio. Color can be useful - - but it is easy to confuse the white gears with the yellow gears after extended use in a transmission.

The 81-83 280ZX's with 5spd. came with 3.545 and 3.9 rear end ratio's. However your 240Z could have it's stock 3.364 or 3.545 if it was an A/T. Or your 240-Z might have had its rear gear changed along with the installation of the 5spd. tranny.

16 Teeth, Yellow, 3.364 rear gear

17 Teeth, Black, 3.545

18 Teeth Blue, 3.7

19 Teeth White, 3.9

20 Teeth Red 4.11

FWIW,

Carl B.

Thanks Carl great data!

My prior 73 240z that I referenced above did have a 17 tooth gear - so it must have been the Black one. Must have had a stock 3.545 rear end in it.

My current '73 240z has the 3.9 rear end with an '82 280zx 5spd and I know that's a 19 teeth speedo gear - this must have been the white one that I replaced when I had the transmission dropped and rebuilt as well. This gear was fine and I had no speedo bouncing - but I bought a new gear anyway and replaced it as a precaution.

Many thanks again ..

Thought I would append my question on this thread. I have an R200 diff matched with a 3.9 5 speed from an 83 280zx installed in my 70 Z, along with the white pinion gear (white). I am running the standard 14" wheels with standard size tires. I am finding that my speedo is off by about 10% on the high side and was wondering if I should change to a different pinion gear to have more accuracy. Any thoughts?

Thanks!

Thought I would append my question on this thread. I have an R200 diff matched with a 3.9 5 speed from an 83 280zx installed in my 70 Z, along with the white pinion gear (white). I am running the standard 14" wheels with standard size tires. I am finding that my speedo is off by about 10% on the high side and was wondering if I should change to a different pinion gear to have more accuracy. Any thoughts?

Thanks!

That's a lot of work for 10 percent improvement. I would leave it alone.