Speedometer

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Category: Body Electrical System

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Revision as of 02:49, 3 May 2009 ddgonzal (Talk | contribs) (->Drive Ratios) <- Previous diff		Revision as of 03:03, 3 May 2009 ddgonzal (Talk | contribs) (->Drive Ratios) Next diff ->
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	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 = 29.4 teeth, the closest is the 20 tooth cog.		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 = 29.4 teeth, the closest is the 20 tooth 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.	+	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.
	<table width=50% bordercolor=black border=1>		<table width=50% bordercolor=black border=1>
-	<tr><td>Teeth</td><td>% change</td><td>50 mph reading</td></tr>	+	<tr bgcolor=ccccff><td>Teeth</td><td>% change</td><td>50 mph reading</td></tr>
	<tr><td>16</td><td>106.25%</td><td>53.1</td></tr>		<tr><td>16</td><td>106.25%</td><td>53.1</td></tr>
	<tr><td>17</td><td>100.00%</td><td>50.0</td></tr>		<tr><td>17</td><td>100.00%</td><td>50.0</td></tr>
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	</table>		</table>
		+
		+	Correction Table, increase Teeth by:
		+	<table border=1 cellspacing=0 width=100%>
		+	<tr bgcolor=ccccff><td> Actual mph</td><td> Desired mph</td><td> Tooth </td></tr>
		+	<tr><td> 40 </td><td> 50 </td><td> 3+ </td></tr>
		+	<tr><td> 43 </td><td> 50 </td><td> 2+ </td></tr>
		+	<tr><td> 47 </td><td> 50 </td><td> 1+ </td></tr>
		+	<tr><td> 50 </td><td> 50 </td><td> 0+ </td></tr>
		+	</table>
		+
		+
		+	== Part Numbers ==
	* NOTE: while they are color-coded, order by part number, not by color. For example, 63-series and 56-series cogs (pinion gears) use different color coding.		* NOTE: while they are color-coded, order by part number, not by color. For example, 63-series and 56-series cogs (pinion gears) use different color coding.
	* They are easy to replace by removing the roll pin...use your original Cog Body.		* They are easy to replace by removing the roll pin...use your original Cog Body.
-	== Part Numbers ==
	[[56-Series Transmission]] and [[60-Series Transmission]]		[[56-Series Transmission]] and [[60-Series Transmission]]
	* 32703-15400 PINION SPEEDOMETER 17T [White]		* 32703-15400 PINION SPEEDOMETER 17T [White]

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Revision as of 03:03, 3 May 2009

Speedometers were either in kilometers (JDM) or miles (USA). Australia started with mph and then switched to kph. Some speedometers had a trip meter.

Comparo

1972 USA Owners manual (see page 8,9 for Speedometer): Instrument and Controls

Contents 1 Variations 2 Metric-Imperial Conversion 2.1 Speedometer Calibration 2.2 Amplifier Speed Switch 3 Custom Faces 4 Speedometer Cable 4.1 Cable Breaks 5 Drive Ratios 5.1 Part Numbers 6 Photo Index

Variations

•  ?? 100MPH w/o tripmeter (US standard equipment)

  

•  ?? 100MPH with tripmeter

  

• 24850-H3400 1200 120MPH SPEEDOMETER Includes tripmeter

  

• Facelift GX - 180 kph

  

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 Calibration

There are two basic reasons for speedos reading fast or slow:

1. Factory speedometer tolerance is usually 5% fast to 10% slow (this is in general, I don't know what Nissan's specs are)

   1200 Top Speed discusses this. One magazine test noted the 1200 speedometer in the test car was 7% slow. My 1200s have been between 7.5% - 10% slow (with stock running gear include tire size). Also see speedo off

2. Different size tires than original, changed diff ratio or transmission

For the latter, there is a mechanical solution of changing to the appropriate speedo-drive gear at the back of the transmission:

For the former, where you have the "right" size tires, final gear ratio and stock transmission -- the speedometer itself may be calibrated.

Where can you go to get a speedo calibrated? Can it be done at home?

• MGA Guru: Speedometer calibration

• Scale Adjusted for low gearing, looks good printed on photo paper and bolted to speedometer.
• I modified mine to change the scale since I didn't want to get under the car and change the plastic speedo gears.

Amplifier Speed Switch

USA model from 0772 use an amplifier speed switch.

• 25035-H7000 ASSY-AMPLIFIER SPEED SWITCH

Australia models also used it, dates unknown.

Custom Faces

See Custom Dash Faces

Speedometer Cable

The cable for manual transmission and Automatic are different

Rockauto.com $7.76

Nissan Part Numbers

B10

• 25058-89914 ASS'Y-SHAFT, flexible speedometer B10 M/T
• 25058-89915 ASS'Y-SHAFT, flexible speedometer B10 Automatic

B110 - both interchange

• 25058-H1000 ASS'Y-SHAFT, flexible speedometer Length=1500 NLA
• 25058-H1001 ASS'Y-SHAFT, flexible speedometer Length=1400 NLA

B210

• 25050-H5000 ASS'Y-SHAFT, flexible speedometer Length=1700
  • B5050-Y8101 supercedes 25050-H5000 $51.22
• 25050-H5900 ASS'Y-SHAFT, flexible speedometer Length=1650 w/Master Vac NLA
• 25050-H7403 ASS'Y-SHAFT, flexible speedometer w/63-series trans
• 25050-H7410 ASS'Y-SHAFT, flexible speedometer A14 automatic
• 25050-H7411 ASS'Y-SHAFT, flexible speedometer A12

Cable Breaks

The speedometer cable usually lasts forever. There are two common reasons why it will break:

1. Mechanical kink or breakage, for example if you drive over a tree branch and it pulls the cable
2. Bad or missing engine ground wire.

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I think you'll find this is caused by poor/dirty ground strap from the engine to the body inside the engine bay.

It only takes once, and the cable it screwed, as it melts the nice polyethylene coating on the inside.

See how the cable's protective plastic appear worn..I'd say it melted during starter crank. Then when the cable gets some speed up, the plastic grabs and the cable snaps.

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Drive Ratios

Stock 1200 Speedometer gear ratio:

• 17/5 (17 tooth pinion, 5 tooth worm drive on trans output shaft)
• 18/5 for Wagon

Available ratios

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

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 = 29.4 teeth, the closest is the 20 tooth 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.

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+

Part Numbers

• NOTE: while they are color-coded, order by part number, not by color. For example, 63-series and 56-series cogs (pinion gears) use different color coding.
• They are easy to replace by removing the roll pin...use your original Cog Body.

56-Series Transmission and 60-Series Transmission

• 32703-15400 PINION SPEEDOMETER 17T [White]
• 32702-15400 ASSY-PINION SPEEDOMETER 17T
• 32703-H1000 PINION SPEEDOMETER 18T
• 32702-H1000 ASSY-PINION SPEEDOMETER 18T (B120, 1975-1979)
• 32702-H1001 ASSY-PINION SPEEDOMETER 19T (B120, 1980 up)

Automatic Transmission

• 32703-P2621 PINION SPEEDOMETER 20T (auto)
• 32703-P2620 PINION SPEEDOMETER 20T (auto)
• 32702-P2719 ASSY-PINION SPEEDOMETER 19T (auto)

63-Series Transmission

• 32703-N9016 PINION SPEEDOMETER 16T
• 32703-N9018 PINION SPEEDOMETER 18T
• 32703-N9019 PINION SPEEDOMETER 19T

Photo Index

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