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Hey Everyone,

 

I want to first thank everyone on answering some of the previous questions on my past post here.

 

I got a cluster out of a 1994 XJ 6 cylinder.

I wanted to swap it into my 1991 MJ 4 cylinder.

I did search online about the swap and i saw that very early clusters can be dropped in as those use speedometer cables instead of a speed sensor in the transmission.

 

I want to get rid of the idiot lights cluster. 

 

Can this 1994 be dropped in it? Or any mods to make the tach work are needed?

I already sort out the sensors for it.

 

Any inputs would be very welcome.

 

Thanks again!

 

Regards

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The speedometer won't work with the '91 speed sensor. The '94's is a three-wire hall-effect sensor, whereas the '91 uses a two-wire setup. You could in theory swap out the VSS for the correct one, but then you'd have to pull the main wiring harness apart to add a wire and new connectors.

The tach I don't know so much about, but I'm pretty sure the six-cylinders won't read accurately with a four-cylinder. Some of them might be adjustable?

It would probably be easier to pull another cluster from a '91 to early '93 XJ/MJ four-cylinder for plug and play.

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The speedometer won't work with the '91 speed sensor. The '94's is a three-wire hall-effect sensor, whereas the '91 uses a two-wire setup. You could in theory swap out the VSS for the correct one, but then you'd have to pull the main wiring harness apart to add a wire and new connectors.

The tach I don't know so much about, but I'm pretty sure the six-cylinders won't read accurately with a four-cylinder. Some of them might be adjustable?

It would probably be easier to pull another cluster from a '91 to early '93 XJ/MJ four-cylinder for plug and play.

WIth the later model IC, 4 cyl vs 6cyl doesn't matter. It was the early 84-86 IC, that could be swapped into renix-era heeps that was cylinder dependent. So, tach should work. 

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Hey,

Thanks for replies everyone.

So I got an early model cluster that is before the 91 date, so the case is the blue one with the speedometer driven by a cable. I then took it apart and compared against the speedometer of the 94 XJ, which has a white case. 

My cluster that came with the 1991 comanche, is a white case as well. I think the case color denotes the generation, or cluster revision used. 

I did see that for the tach, there is an adjustable potentiometer on the board, so It seems that I can adjust the tach to match the 4 cyl since it came out of a 6 cyl.

 

Ill keep you guys posted. 

The car is all apart as I am doing a bunch of fixes. this also included replacing the dashboard, since the one that came with it was completely torn, cracked and ripped.

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The speedometer won't work with the '91 speed sensor. The '94's is a three-wire hall-effect sensor, whereas the '91 uses a two-wire setup. You could in theory swap out the VSS for the correct one, but then you'd have to pull the main wiring harness apart to add a wire and new connectors.

The tach I don't know so much about, but I'm pretty sure the six-cylinders won't read accurately with a four-cylinder. Some of them might be adjustable?

It would probably be easier to pull another cluster from a '91 to early '93 XJ/MJ four-cylinder for plug and play.

Hey

 

Thanks for letting me know about the sensor and wire. 

Do you know which sensor I should be using on a 4 speed AX trans?

I don't mind buying a new sensor, so i can be plug and play for me :)

Or the other option I got, is to pull the speed sensor out of the car that I got the cluster from at the junkyard. Its a 1994 Xj with an auto. Will that speed sensor even work with my manual trans?

 

I have the car apart right now fixing other issues, including a dash replacement, so I don't have a problem to run extra wires.

 

Thanks again for the reply.

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You need a 1991-1996 cluster with a white case. Don't mess with the speedo sensor. The VSS comments above are incorrect. If the tach is adjustable, you will be able to use it on your 4 banger. I'm not sure what years were adjustable and which weren't.

 

I have a 1996 OBD2 cluster in my 1991 truck and everything works like it's supposed to. Speedo, tach, volt meter, and the warning lights on the left side of the cluster will work out of the box. You will need to replace a couple of sensors to make the oil pressure and temp gauges work. One oddity of the 1991 is that it uses Renix (1987-1990) senders for the oil pressure and water temperature gauges.

 

Make sure to specify that you need the sensors for the GAUGES, not the LIGHTS. Parts drones sometimes don't pick up on this important difference - or you can cut out the middleman and get them online (I tend to prefer Rockauto.com)

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Maybe the speedometer interprets the different signals the same way, I don't know. But there very definitely is a very significant difference in the VSS. I just swapped a late '93 drivetrain into my '91, and there was no way the later VSS would have worked with my '91's harness.

I guess the only way to find out is to plug in the gauge cluster and find out?

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Some time around '93 the VSS changed from the 2-wire thing to a 3-wire sensor (and with that change came the short-shaft speedometer gears), but the cluster will treat it the same way. Worked for me. Yet another oddity with the early HO trucks.

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^^ This. The 91-96 speedos are all the same electrically (just a trip meter difference) and will interchange and function throughout the OBD1 years. I used a 95 cluster in my 91 when I swapped it in to replace the idiot light cluster and it worked fine. Then swapped in my original 91 speedo which also worked fine. There is only one input signal connection to the cluster for all the OBD1 speedos, and the VSS doesn't matter. I "think" the 3rd wire on the 93? and above VSS is an input to the ECU only. But have not bothered to verify since the speedo has worked fine for me in several configurations.

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^^ This. The 91-96 speedos are all the same electrically (just a trip meter difference) and will interchange and function throughout the OBD1 years. I used a 95 cluster in my 91 when I swapped it in to replace the idiot light cluster and it worked fine. Then swapped in my original 91 speedo which also worked fine. There is only one input signal connection to the cluster for all the OBD1 speedos, and the VSS doesn't matter. I "think" the 3rd wire on the 93? and above VSS is an input to the ECU only. But have not bothered to verify since the speedo has worked fine for me in several configurations.

From what I could gather. The three wire sensors are an active speed sensor. meaning they take Ground, Power and then signal out. This signal is a nice digital signal, or square wave. 

A two wire speed sensor is a passive device on which the only wires are ground and signal. On these, the signal output will be sinusoidal, which is more prone to noise. 

However the cluster is just looking for a frequency input, which both sensors will supply. 

This is the reason using either sensor should work.

I havent fitted the cluster yet, but I feel that this is the reason it works. This is from experience on setting up pickup sensors for engine crankshaft and camshaft pickups for aftermarket programmable ECUs

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From what I could gather. The three wire sensors are an active speed sensor. meaning they take Ground, Power and then signal out. This signal is a nice digital signal, or square wave. 

A two wire speed sensor is a passive device on which the only wires are ground and signal. On these, the signal output will be sinusoidal, which is more prone to noise. 

However the cluster is just looking for a frequency input, which both sensors will supply. 

This is the reason using either sensor should work.

I havent fitted the cluster yet, but I feel that this is the reason it works. This is from experience on setting up pickup sensors for engine crankshaft and camshaft pickups for aftermarket programmable ECUs

 

Correct. The 91 VSS is nothing but a make/break reed switch that sends a pulsing sine wave signal to the speedo relative to the rotation of the transmission (2WD) or transfer case (4WD) output shaft. It's easy to check with an analog ohmmeter by jacking up the rear wheel, disconnect the VSS and place the meter across the two leads. The needle should deflect indicating the switch is opening/closing as the rotor moves past the sensor.

 

Have not worked with the 3-wire VSS's yet, but it should be the same procedure except use a voltmeter to watch the pulses out. Or an o-scope.  :yes:

 

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