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speedo help please - reading high


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like 100mph at 65mph

unknown diff ratio (320i lsd)


if i have a 3:91 dif and the speedo is geared for a 3:64 that would do it wouldn't it?

plus.... how do you get the speedo needle off? and on?

First, check the back of the speedometer for the "W" value.

3.45:1 diff -- W=1.24 speedo

3.64:1 diff -- W=1.297 speedo (W=1.30 is close enough)

3.90:1 diff -- W=1.39 speedo ('76 49-State 2002)

3.91:1 diff -- W=1.393 speedo (E21 320is LSD)

4.10:1 diff -- W=1.4 speedo (1.461 calculated)

4.11:1 diff -- W=1.4 speedo (1.465 calculated)

4.38:1 diff -- W=1.559 speedo (calculated)

Yes, if you have a deeper diff ratio (higher number) than for which your speedometer is geared, it will read high. However, given the huge gap, I suspect that your needle may be off.

The needle is press-fit. It will take some careful yet forceful screwdrivering to get it off. If you hook up a variable speed drill to the cable, you can calibrate the needle:

1. Spin the cable until the needle hits exactly 60 MPH.

2. Use a stopwatch to time the odometer for 1 mile.

3. If the time to 1 mile is less than 1 minute, remove the needle and replace it a few degrees clockwise; if the time to 1 mile is more than 1 minute, remove the needle and replace it a few degrees counterclockwise. Of course, setting hte needle means pressing it on and then carefully moving it over the needle stop.

4. Repeat until 60 MPH = 1 minute/mile on the odometer.

Once that is set, figure out what diff ratio you have and match it to the speedometer by replacing one or the other.

Good luck!

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than a needle adjustment...

Does it...read kinda accurately at lower speeds, and then once you're up to 40 or so it starts to read way high? If so, probably the two drive disks inside the speedo are touching (they're not supposed to).

You may be able to fix it pretty easily. I did a column on how to; drop me an e-mail and I'll send it to you.

Usually when a speedo needs adjustment it's only reading a few mph or % points higher or lower than normal--not 35 mph!

And BTW it's really difficult to get the needle off the shaft without boogering something up. I'm sure there's a trick or a tool, I just haven't learned it yet!



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go to north hollywood speedometer's website

pull down the calibration work sheet.

measure the cable turns.

fill out cal sheet

send sheet and speedo head to nhs

check your mailbox in a week for a beautifully rebuilt and ACCURATE speedo.

worked for me!

I really like North Hollywood Speedometer's work, but they're expensive! Of course, that is why I am currently attempting to convert my speedometer to an electric unit in my apartment. I'll let you know how that one goes.

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