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Speedometer / odometer issues


mr928

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There is a gear on the mainshaft of the transmission that turns a gear mounted on a plug that goes into the transmission, near the back of the transmission. A cable screws on the outside pf this plug. When the transmission mainshaft turns, the gear, and the cable inner part turns.

The other end of the speedometer cable screws on the back of the speedometer. Inside the speedometer, are more gears, to drive the odometer, and there is a magnet inside an aluminum cup, that works against a spring, to drive the speedometer.

 

The point is, if both the speedometer, and odometer quit, probably a bad cable.

 

Unscrew the cable from the back of the speedometer. When the rear wheels turn, does the inner cable turn? if no, the inner cable may be broken. It is also possible the outer cable housing hooked something, and got stretched. Follow the outer cable from the speedometer, through the firewall, looped past the steering column, down under the truck, to the transmission. Look for Damage.

Unscrew the cable from the plug on the transmission, and get a flashlight. Be careful you have to block the reat wheels off the ground, and turn then, with you under the truck. There is no need to run the engine, just have somebody turn the wheels by hand, with the transmission in neutral. With the rear wheels turning, can you see the end of the speedometer gear turning?

 

If it turns, the cable is bad. If no turning on the speedometer pinion, it could be bad,

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Sorry about the lack of info. I should know better as I sell auto parts for a living.

 

1970 521.

The cable does turn at the back of the cluster so I assume the problem is internal to the speedo. The local speedo shop bench tested it and confirmed the same but claims he cannot find the gear that goes on the odometer but he can make the speedo functional.

 

 

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It is a 42 year old Japanese vehicle. It could be very possible your speedometer guy called the local Nissan dealer, and was told the part was NLA.

 

This board is probably one of the best sources for getting used parts for your truck. Start looking in local junkyards.

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It is a 42 year old Japanese vehicle. It could be very possible your speedometer guy called the local Nissan dealer, and was told the part was NLA.

 

This board is probably one of the best sources for getting used parts for your truck. Start looking in local junkyards.

 

 

Thankd Daniel,

I will start looking at the local yards as there are several things I need or at least would like to have. The truck is so original and nice I'd really like to address the few issues and make it near perfect. I need a column switch and the junk yard wanted $125 but I found it new for $150. I still have not pulled the trigger on it as I was hoping to find it for less. I also need a clutch hose and a flasher switch.

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Brake lines, and clutch lines lines, like the body bolts are SAE. That is, if nobody changed them.

the clutch slave cylinder is probably not stock.

The thread on the flare nuts that screw into the hydraulic parts should be 3/8-24. This is the size of flare nut usually on a 3/16 brake line.

 

By column switch, I think you mean the turn signal, headlight dimmer switch. Try to take it apart, and just clean 42 years of gunk out of it. It might work after cleaning the old fish oil grease out of it.

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Your turn signal switch looks good, except the center wire has come unsoldered. Have someone re-solder it and put it back in. I fixed mine six years ago and it's still working like a champ.

 

 

I wish it was as simple as soldering the wire back on but the no conductive plate is broken and the ball is missing for the contact.

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  • 1 year later...

I've had my Datsun 521 for a few months now and haven't had a working speedometer/odometer the entire time. This is extremely helpful and will be testing this out as soon as I get access to a driveway.

 

There is a gear on the mainshaft of the transmission that turns a gear mounted on a plug that goes into the transmission, near the back of the transmission. A cable screws on the outside pf this plug. When the transmission mainshaft turns, the gear, and the cable inner part turns.
The other end of the speedometer cable screws on the back of the speedometer. Inside the speedometer, are more gears, to drive the odometer, and there is a magnet inside an aluminum cup, that works against a spring, to drive the speedometer.

The point is, if both the speedometer, and odometer quit, probably a bad cable.

Unscrew the cable from the back of the speedometer. When the rear wheels turn, does the inner cable turn? if no, the inner cable may be broken. It is also possible the outer cable housing hooked something, and got stretched. Follow the outer cable from the speedometer, through the firewall, looped past the steering column, down under the truck, to the transmission. Look for Damage.
Unscrew the cable from the plug on the transmission, and get a flashlight. Be careful you have to block the reat wheels off the ground, and turn then, with you under the truck. There is no need to run the engine, just have somebody turn the wheels by hand, with the transmission in neutral. With the rear wheels turning, can you see the end of the speedometer gear turning?

If it turns, the cable is bad. If no turning on the speedometer pinion, it could be bad,

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