Speedo Box Location

[ViperC]

I want to swap gears. I have 3.55s right now and the speedomoter is correct. I just cant locate the speedo box. I know they're usually near the PCM, but mine is not. Could it be behind the dash? I know some people claim that you can adjust the speedo with a tuner, so maybe that's whats happened? The 3.55s have been there pretty much since the car was first bought. Any help?

[dave6666]

It could be in the tunnel near the sensor on the transmission.

[1BADV10]

I'm curious what you don't like about the 355's? I'm thinking of swapping my 307's to 355's soon.

[dave6666]

I'm curious what you don't like about the 355's? I'm thinking of swapping my 307's to 355's soon.

Where in his post does it say anything about liking the gears or not? Actually reading the post shows he's asking where the speedo cal box is.

[The Stig]

mine was behind the cover for the PCM... if u can trace the speed sensor wire out of the PMC it only goes to the tranny , like dave says tunnel... there is only so much distance or wire

[1BADV10]

Where in his post does it say anything about liking the gears or not? Actually reading the post shows he's asking where the speedo cal box is.

Well Dave6666, his post starts with "I want to swap gears. I have 355's right now and the speedometer is correct." That part of the post tells me he has 355's he is swapping out for some reason. I was curious why, simple question for ViperC, not Dave6666.

[Matt M, Pa]

In my Gen 1.5, (if memory serves) it's near the instrument cluster. I believe it's visible if I pull the driver's side knee bolster.

[ViperC]

I'm curious what you don't like about the 355's? I'm thinking of swapping my 307's to 355's soon.

I like 3.55s. I want even more gear though since I am using a taller tire now.

[ViperC]

In my Gen 1.5, (if memory serves) it's near the instrument cluster. I believe it's visible if I pull the driver's side knee bolster.

Do you just have to remove the 4 screws that hold the knee bolster in place?

[Luisv]

I want to swap gears. I have 3.55s right now and the speedomoter is correct. I just cant locate the speedo box. I know they're usually near the PCM, but mine is not. Could it be behind the dash? I know some people claim that you can adjust the speedo with a tuner, so maybe that's whats happened? The 3.55s have been there pretty much since the car was first bought. Any help?

It can really be installed anywhere. Assuming you simply run wiring.

However, I have mine inside the metal cover for the PCM on the driver's side. It's in the lower "slanted" section. This is typically where it's placed because you can wire it up without having to run a ton of wire.

Depending on the box used, they can be configured to adjust for differences. The one I have and I have seen most use is the Unitrax box.

[ViperC]

It can really be installed anywhere. Assuming you simply run wiring.

However, I have mine inside the metal cover for the PCM on the driver's side. It's in the lower "slanted" section. This is typically where it's placed because you can wire it up without having to run a ton of wire.

Depending on the box used, they can be configured to adjust for differences. The one I have and I have seen most use is the Unitrax box.

Unfortunately mine is not there. The gear swap was done in '98 and the speedo box hasn't been seen since! lol

[Luisv]

Unfortunately mine is not there. The gear swap was done in '98 and the speedo box hasn't been seen since! lol

OK. Then there are not many options.

The speed sensor on the T56 in the Gen 2's is on the tail housing below the reverse lockout solenoid. Its on the driver's side of the trans. The reverse lockout solenoid is the closest to the top of the trans, near the shifter that comes out 90 degrees to the trans and the connector points back towards the rear of the car. The speed sensor is just below that. I mention this for two reasons. First, this is the wire you'll have to trace back to find the speedo box. If it's not at the PCM, it could be there. The second reason I mentioned the sensor location is that they may have simply replaced the sensor with one calibrated differently. At the end of the day, it's simply a gear driven unit that sends out a voltage. If you change the unit, it could simple be adjusted for the 3.55 gears. This was done 20 years ago hard to know what was done.

The only other place it could be is behind the driver's side knee panel. There is plenty of space up there, but that is, by far, the hardest place to look. Frankly, the hardest place to install it. In the end, however, the speedo boxes simply adjust the voltage getting to the speedo to vary its reading. It could be just before the speedo.

There are two last places you may want to try... check on the driver's side kick panel. The panel at the base of the a-pillar in front of the door hinge inside the car. It could be there. The only other possibility that comes to mind, the painted panel on the outside. The panel that is just in front of the door at the side gill. The wire harness that leads from the PCM enters the passenger compartment there. Maybe they tapped in there and left the box behind the panel. Worth a shot.

[ViperC]

OK. Then there are not many options.

The speed sensor on the T56 in the Gen 2's is on the tail housing below the reverse lockout solenoid. Its on the driver's side of the trans. The reverse lockout solenoid is the closest to the top of the trans, near the shifter that comes out 90 degrees to the trans and the connector points back towards the rear of the car. The speed sensor is just below that. I mention this for two reasons. First, this is the wire you'll have to trace back to find the speedo box. If it's not at the PCM, it could be there. The second reason I mentioned the sensor location is that they may have simply replaced the sensor with one calibrated differently. At the end of the day, it's simply a gear driven unit that sends out a voltage. If you change the unit, it could simple be adjusted for the 3.55 gears. This was done 20 years ago hard to know what was done.

The only other place it could be is behind the driver's side knee panel. There is plenty of space up there, but that is, by far, the hardest place to look. Frankly, the hardest place to install it. In the end, however, the speedo boxes simply adjust the voltage getting to the speedo to vary its reading. It could be just before the speedo.

There are two last places you may want to try... check on the driver's side kick panel. The panel at the base of the a-pillar in front of the door hinge inside the car. It could be there. The only other possibility that comes to mind, the painted panel on the outside. The panel that is just in front of the door at the side gill. The wire harness that leads from the PCM enters the passenger compartment there. Maybe they tapped in there and left the box behind the panel. Worth a shot.

Thanks! I will try those spots!

[Matt M, Pa]

Do you just have to remove the 4 screws that hold the knee bolster in place?

Yes, just those 4 screw retain the bolster. I don't recall if there is a metal plate behind the bolster...but it would come out in a similar fashion. I don't recall any issues getting to it when I was swapping out the dash and working around that area...

[jdeft1]

I located the 'Yellow Box' speedo calibration unit inside the passenger side foot-well, opposite where the PCM is located outside.....

[ViperC]

I located the 'Yellow Box' speedo calibration unit inside the passenger side foot-well, opposite where the PCM is located outside.....

So it was outside the cabin?