![[Datsun 1200 encyclopedia]](/wiki/upload/wiki.png)
Speedometers were either in kilometers (JDM) or miles (USA). Australia started with mph and then switched to kph. Some speedometers had a trip meter.
Contents |
Overview
Comparo 
1972 USA Owners manual (see page 8,9 for Speedometer):
Instrument and Controls
Variations
- ?? 100MPH w/o tripmeter (US standard equipment)
-
- ?? 100MPH with tripmeter
-
- 24850-H3400 1200 120MPH SPEEDOMETER Includes tripmeter
-
- Facelift GX - 180 kph
-
Part Numbers
USA
- 24850-H1816 ASSY-SPEEDOMETER 100MILE/H
- 24850-H7000 ASSY-SPEEDOMETER 100MILE/H From 7/72 [With 10 mph markings]
JDM Sunny Truck
- 24850-B8600 SPEEDOMETER ASSY -7803 [Rectangle]
- 24850-G1670 SPEEDOMETER ASSY 7804- [Round]
Metric-Imperial Conversion
Sometimes on eBay Australia you can get the vintage conversion stickers.
OR
Take the face plate and scan it on the flatbad scanner, then modify it. Finally, print a new one out with the photo printer. You can modify the font, colors, etc. Bolt it to the speedo using the standard screws.
Speedometer Calibrationon =
It is normal for the speedometer to read fast. The specified tolerance is +5% -10%. So at actual 60mph it can read 57 to 66 and still be acceptable.
But you can blueprint the speedometer to be closer to the actual speed.
See Speedometer Calibration
Amplifier Speed Switch
USA model from 0772 use an amplifier speed switch for Throttle Opener system.
25035-H7000 ASSY-AMPLIFIER SPEED SWITCH
Australia models also used it, dates unknown.
68800-AM7200 speed sensor
Datsun 620 pickup USA also uses it for BCDD system:
620 clusters with Amplifier Speed Switch attached to back of speedometer
25035-H7000 ASSY-AMPLIFIER,SPEED SWITCH $69 USD * Datsun 1200 1973 USA * Datsun 620 1972 USA MT 25035-B6401 $88 USD * Datsun 620 1974 USA MT 25035-B8000 $70 USD * Datsun 620 1975-1979 USA MT
Custom Faces
280Z speedometer fits:
- Swap the mounting cups as the 280Z unit is deeper
- Drill a hole for the trip meter shaft through the back
- The face is to large for the opening in the 1200 housing, so carefully reduce the diameter by 1/8 inch
Speedometer Cable
See main article: Speedometer Cable
Drive Ratios
Stock 1200 Speedometer gear ratio:
- pinion teeth/worm teeth on trans output shaft
- 17/5 (3.90 diff)
- 18/5 for Wagon or Ute (4.11 diff)
To adjust the speedometer for different diameter tires, change the transmission cable pinion cog.
* If speedo reads too fast, fit a bigger cog * If speedo reads too slow, fit a smaller cog
Given that stock is a 17 tooth pinion, moving to one more or less tooth is about 6% change. So by changing the pinion you can only get it to ±3 mph accurate. For example, at 100 mph, within 3 mph. Or at the standard 50 mph rating, a reading between 1½ mph (48½ to 51½) is the best you can hope for. For finer tuning the speedometer itself needs calibration. Or you could fit different diameter rear tires.
EXAMPLE: If you are reading say 60 when you are really going 50 then the speedo cable needs to slow down by about 20% to read more accurately. If the speedo drive has a 17 tooth cog in it try to find a cog that reduces by 20%. 17 X .20 = 3.4 teeth... 17 + 3.4 = 20.4 teeth, the closest is a 20 tooth cog.
| Teeth | % change | 50 mph reading |
| 16 | 106.25% | 53.1 |
| 17 | 100.00% | 50.0 |
| 18 | 94.44% | 47.2 |
| 19 | 89.47% | 44.7 |
Correction Table, increase Teeth by:
| Actual mph | Desired mph | Tooth |
| 40 | 50 | 3+ |
| 43 | 50 | 2+ |
| 47 | 50 | 1+ |
| 50 | 50 | 0+ |
Estimated Tire Correction Table (for 3.9 diff)
| Size | Diameter | Difference | Pinion | ~Error |
| 165/55R12 | 19.1 | 88% | 19T | 0% |
| 165/60R12 | 19.8 | 91% | 18T | -2% |
| 165/70R12 | 21.1 | 97% | 17T | 3% |
| 155/80R12 | 21.8 | 100% | 17T | 0% |
| 175/70R13 | 22.6 | 104% | 16T | 2% |
| 195/50R15 | 22.7 | 104% | 16T | 2% |
| 165/70R14 | 23.1 | 106% | 16T | 0% |
| 205/45R17 | 23.5 | 108% | 16T | -2% |
| 185/60R15 | 23.7 | 109% | 16T/15T | 3% |
| 205/40R18 | 24.5 | 112% | 15T | 0% |
