Speedometer / VSS Wiring - JeepForum.com
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post #1 of 9 Old 11-13-2019, 11:58 PM Thread Starter
88YJtoCJ
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1988 YJ Wrangler 
 
Join Date: May 2009
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Speedometer / VSS Wiring

Okay, another one of my zany wiring threads.


I have been wiring up a 95 Dash into my 88YJ. So far I have every gauge working (with lots of help from here!) except for my Speedometer.


My 88 was Mechanical Cable Driven.


I have purchased the VSS Housing/Adapter for a 95 (The guy that bolts to the T-Case).

I have purchased the VSS for a 95 (The guy that bolts into the Housing).
I have purchased a short shaft #30 gear (my old one was a long shaft #30)


I can bolt all this into the T-Case just fine... but there is nothing wired to anything, as my 88 Never had any wiring.


I found a Picture (attached) that states the 3 wires are as follows:

White/Orange Trace - Signal

Black / LB trace - Ground
Orange - 8 Volt Supply


I have read the Signal wire goes to the PCM, then from the PCM to the Gauge. This leads to my first set of questions:
1a) Does the PCM do any translation / calculation for the Gauge? (I have no PCM).
1b) If yes to 1a, is there an adapter much like the Tach Signal Adapter I am using already? If no to 1a, I will just wire it direct to the gauge signal line



I see the Orange wire is an 8 volt supply this leads to the following set of questions:
2a) Is this a constant 8 volts?

2b) Can I just wire a 12 volt supply to a buck converter to step it down to 8 volts and let that fly as the supply?


If nobody knows, I will attempt to wire it directly to the gauge after I get an 8 Volt supply line situated.


This will answer anyone asking if the PCM is "needed" in a YJ for any purpose other than dummy lights, OBD-II diagnostics,and lots of sensor combinations that kill the engine.

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White 88 YJ = $2000
Straight 6 = $1200
AX15 = $400
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post #2 of 9 Old 11-14-2019, 08:02 AM
fishadventure
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A] YJs are OBD1
B] 88 doesn’t have speed input to computer
C] use your 88 speedo
D] the ‘orange’ wire 91-95 that feeds the speedo is merely connected to the VSS signal to ecu
E] I don’t see any reason to cross-trade your cable speedo to electronic? Unless there’s issue(s) with cable clearance from (like in my case) a flat skid mod or something. I need an electro speedo; 91s came with a cable speedo and a drive that included an electronic pickup for the ecu to see
F] the 8 volts is a base voltage- the sensor pulses voltage to the gauge or ecu and both interpret that

[size=3]Shackles & D-rings are different things.
Cranking IS turning over
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post #3 of 9 Old 11-14-2019, 09:03 AM
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Or install a GPS speedo . Speedhut gauges

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post #4 of 9 Old 11-14-2019, 05:03 PM Thread Starter
88YJtoCJ
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Perhaps I need to be a little more specific.


My 88YJ was gutted and was a Tub, Engine, Frame, and no wiring, no computers, no ECU, no PCM, no sensors of any kind.



I am rebuilding this from the ground up and put a dash in with all gauges and wiring intact from a 95 YJ. I am using a 95 Speedometer because that is what I have. I had hooked up an old school 70's style speedo on a cable just to have a speedo previously, but it does not fit in the Dash.


Simpler question:

Does the output signal from the VSS to the PCM get "translated/converted" to a different signal before it outputs from the PCM to the Speedometer gauge?



I suppose most people wouldn't test this or know, as they generally don't unhook all the sensors and remove the PCM and attempt to keep all the stock gauges. I will give it a whirl and see what happens.

88YJtoCJ

White 88 YJ = $2000
Straight 6 = $1200
AX15 = $400
Sagging Springs = Priceless
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post #5 of 9 Old 11-14-2019, 05:36 PM Thread Starter
88YJtoCJ
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Join Date: May 2009
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So I found my own answer, the PCM does translate the signal. I will need one of these:

https://www.dakotadigital.com/index....rod/prd126.htm

88YJtoCJ

White 88 YJ = $2000
Straight 6 = $1200
AX15 = $400
Sagging Springs = Priceless
88YJtoCJ is offline  
post #6 of 9 Old 11-14-2019, 06:20 PM
fishadventure
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88 doesn’t have an electronic speed sensor
paulhead likes this.

[size=3]Shackles & D-rings are different things.
Cranking IS turning over
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post #7 of 9 Old 11-14-2019, 11:32 PM Thread Starter
88YJtoCJ
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fishadventure, the entire harness has been replaced from a donor jeep that was a 95, I have an electronic speed sensor in it now. The dash is 100% pulled from a 95YJ with all gauges and transplanted into my jeep.


Project was an AMC straight 6 with no wiring, an AX15 from a 98, an NP231 from a 96. The only thing in the jeep that is an 88 is the frame, axles and tub. Hence my "zany wiring threads" I have been figuring out how to hook everything up without a PCM or ECU, as I have a Motorcraft Carb and an HEI distributor and there does not need to be any computers involved, except the Signal Converter for the Tachometer signal, and it looks like a signal converter for the VSS.

88YJtoCJ

White 88 YJ = $2000
Straight 6 = $1200
AX15 = $400
Sagging Springs = Priceless
88YJtoCJ is offline  
post #8 of 9 Old 11-15-2019, 07:03 AM
fishadventure
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Oh perfect!

So for that original ‘88 5 gauge instrument cluster; it has the hand clock right?

How much would it cost me to have you ship it to me? Actually being serious here. 05661 zip for shipping cost

LOL
The 87 I bought has a 94? harness, drivetrain, frame, and such.
Therefore it has a dumb light but no tick-tok-clock

So I don’t really “need” it but I’d sorta like it (and maybe the idiot light panel piece) if you’ve no other use for them.

[size=3]Shackles & D-rings are different things.
Cranking IS turning over
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post #9 of 9 Old 11-15-2019, 10:29 AM Thread Starter
88YJtoCJ
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I don’t have the original cluster. The jeep had been previously abused and pretty well destroyed when I acquired it from a tow company as salvage with a blown motor. I put a flat CJ dash in it for a while with a couple manual gauges, I recently put a YJ dash back in with real wiring harnesses instead of a painless fuse block with crimp connectors to make it “work”.

So I only have a CJ dash with autozone gauges left over.

88YJtoCJ

White 88 YJ = $2000
Straight 6 = $1200
AX15 = $400
Sagging Springs = Priceless
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