Speedometer signal?

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schmiedel

NAXJA Forum User

Location

Mexico (Querétaro)

• Apr 19, 2006

• #1

I was just wondering if someone has information about the speedometer signal. I have seen some electronic recalibrators for about 200USD, so I don't think the signal is a simple voltage that has to be adjusted (200USD would be a ripoff), so it seems to me as if it was some signal (let's say a digital or analog frequency) that has to be altered to get the correct reading.

Is there some literature available about this?

Regards

 

C

ColoradoXJ13

NAXJA Forum User

Location

Boulder, CO

• Apr 19, 2006

• #2

schmiedel said:

I was just wondering if someone has information about the speedometer signal. I have seen some electronic recalibrators for about 200USD, so I don't think the signal is a simple voltage that has to be adjusted (200USD would be a ripoff), so it seems to me as if it was some signal (let's say a digital or analog frequency) that has to be altered to get the correct reading.

Is there some literature available about this?

Regards

Click to expand...

There is a mechanical linkage in the transfercase and you can just get a new gear for about $15 from the dealer and replace it yourself. Search around.

 

S

schmiedel

NAXJA Forum User

Location

Mexico (Querétaro)

• Apr 19, 2006

• #3

I know that, and it's what I'll probably do when I'm finished with lifting / regearing, etc. However, this is more an interest issue than anything else.

Regards

 

Z

zthang43

NAXJA Forum User

Location

WA state

• May 30, 2006

• #4

Did you find any info about this? I'm interested as well, because I can't get the gear I need to calibrate my speedometer correctly, (I need a 45 tooth gear but 42 is the highest available) so I'm thinking of having the electrical guys at work help me rig up a signal calibrator.

 

jwtrapper

NAXJA Forum User

Location

Wetmore, CO

• May 30, 2006

• #5

Superlift makes one but it aint cheap.

 

S

schmiedel

NAXJA Forum User

Location

Mexico (Querétaro)

• May 30, 2006

• #6

Well, my rig has a cable-driven speedometer, so my only option is the gear finally. I first thought it was electrical.

 

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zthang43

NAXJA Forum User

Location

WA state

• May 30, 2006

• #7

Yeah, if yours is cable driven you may as well just buy the gear, shouldn't be more than $15-$20 at the dealer.

My 91 is electronic; I know a number of companies make re-calibrators but they are pretty expensive (I'd rather just have my speedo read 5 or 10 mph off than spend $200). I'm just wondering if anyone knows what kind of signal the VSS puts out; we have some pretty sharp guys in our electrical department here that can probably build me something to alter the signal, if they knew what the signal was.

 

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schmiedel

NAXJA Forum User

Location

Mexico (Querétaro)

• May 31, 2006

• #8

Well, as far as I know the gear can also be bought with the electronic speedometer. However it would really be interesting to know the signal. If you had an osciloscope it would be a piece of cake to find out.

 

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xjbubba

NAXJA Member # 1524

Location

santa barbara, ca

• May 31, 2006

• #9

Guys with Chevy engines generally have to deal with VSS issues. So there is a ton of info on VSS out there. Start here, for more info: http://www.fullsizechevy.com/forums/showthread.php?t=93742

 

L

lawsoncl

NAXJA Forum User

Location

North Idaho

• Jun 2, 2006

• #10

According to a 95 FSM, the Speedo should be putting out a 122.2 Hz pulsetrain at 55 mph which translates to the slightly easier to remember 8000 pulses per mile. Shouldn't be too hard to make a calibrator... You could go all digital, or it might be easier to convert the frequency to analog, tweak the voltage, and then do an analog-to-frequency stage.

What are you running that you need a 45 tooth? That's like running 4.56 gears and 28" tires!