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Unread 08-11-2014, 06:48 AM   #1
YJTim89
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Older YJ gauges with a new engine? What needs to change?

So I'm in the process of planning for an engine swap for my 1989 4.2 YJ which came to me without an engine, trans, or transfer case. The plan is to take the engine, transmission, transfer case, and wiring harness from a donor WJ Grand Cherokee I got for free from my dad and transplant it in the YJ.

So far most of it seems pretty straightforward but I've been wondering about the gauges. I believe the 87-90 YJs had a mechanical speedometer and tachometer and the rest of the gauges were electronic. My question is can I use these older gauges on a newer engine and harness that was originally electronic? If not what will I need to change?

I'm on a tight budget for this project so cheaper is better.

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Unread 08-11-2014, 07:09 AM   #2
superj
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i think you might be in trouble, unless you can figure a way to hook your speedo to the tcase from the wj. or use the yj tcase on that trans
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Unread 08-11-2014, 07:24 AM   #3
Old4X
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You will need a post 91 wiring harness, tach and speedo at the very least.
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Unread 08-11-2014, 07:27 AM   #4
YJTim89
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Originally Posted by superj View Post
i think you might be in trouble, unless you can figure a way to hook your speedo to the tcase from the wj. or use the yj tcase on that trans
I've seen this done to the 231 with some chevy conversions. Not sure what it would entail though.
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Unread 08-11-2014, 07:28 AM   #5
YJTim89
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Originally Posted by Old4X View Post
You will need a post 91 wiring harness, tach and speedo at the very least.
I was thinking I'd probably need the tach and speedo but why the harness?
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Unread 08-11-2014, 10:47 AM   #6
snowplowdog
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Because the speedo on the older yj is cable controlled and the new one is electronic. You're going to run into the same thing with the center guage cluster. Its different so it probably wont work off the new harness. Are you installing the engine with a carb or FI?
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Unread 08-11-2014, 11:01 AM   #7
YJTim89
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It's fuel injected. We're using the "clean sheet" 4.0 that was used on the 1999-2004 Grand Cherokee and the 2000-2006 TJ. We're taking everything plus the entire harness from our donor.

So if I get gauges from a 91+ YJ will they work with the new harness or am I going to need aftermarket gauges? What would you suggest?
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Unread 08-11-2014, 11:06 AM   #8
JeeperDon
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You might be able to use the older YJ black plastic speedo t-case housing (for a cable) in the WJ t-case. I don't think the t-cases changed much. The tach feed for a OBDII motor comes from the pcm usually, so the signal shape and pulse counts may be different. The newer pcm also gets and uses the speed info from the vehicle to help with throttling down (like coasting to a traffic light). The pcm is not too happy if it thinks you are always parked.

DakotaDigital.com has adapter boxes for these two gauges. I used their SGI-8 and SGI-5 in my case. But I have a '93 which already had electronic VSS t-case output, so easy to connect to their box to feed speed info to my pcm. That would be another option, get the gauge cluster from a newer YJ, but you'd still likely need those two converter boxes.
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Unread 08-11-2014, 11:25 AM   #9
YJTim89
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Originally Posted by JeeperDon View Post
You might be able to use the older YJ black plastic speedo t-case housing (for a cable) in the WJ t-case. I don't think the t-cases changed much. The tach feed for a OBDII motor comes from the pcm usually, so the signal shape and pulse counts may be different. The newer pcm also gets and uses the speed info from the vehicle to help with throttling down (like coasting to a traffic light). The pcm is not too happy if it thinks you are always parked.

DakotaDigital.com has adapter boxes for these two gauges. I used their SGI-8 and SGI-5 in my case. But I have a '93 which already had electronic VSS t-case output, so easy to connect to their box to feed speed info to my pcm. That would be another option, get the gauge cluster from a newer YJ, but you'd still likely need those two converter boxes.
Thanks for the info. Problem with the first option would be that I don't have the original transfer case (plus the WJ has a 242 not a 231) and it looks like the PO cut the speedo cable :

So I'd need to get gauges from a newer YJ and then the adapter boxes to make them function? Would it be cheaper then to just buy new aftermarket gauges?
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Unread 08-11-2014, 03:22 PM   #10
superj
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Intellitronics makes badass gauges that don't need the speedo or anything. Works off gps
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Unread 08-11-2014, 05:55 PM   #11
dfeland
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What engine is it? If it is a 4.0 just get a 91 harness and computer that is ODB1 and use the speed sensor from the 91. All sensors from the 91 will work with your gauges.
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Unread 08-12-2014, 06:44 AM   #12
YJTim89
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Originally Posted by dfeland View Post
What engine is it? If it is a 4.0 just get a 91 harness and computer that is ODB1 and use the speed sensor from the 91. All sensors from the 91 will work with your gauges.
Thought about that too. Problem is that we need the WJ harness for the newer engine, the WJ transmission, and the transfer case.
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Unread 08-12-2014, 07:04 AM   #13
Que89YJ
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What year WJ?
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Unread 08-12-2014, 07:49 AM   #14
YJTim89
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what year wj?
1999
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Unread 08-13-2014, 08:49 AM   #15
YJTim89
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I suppose option B would be to grab the entire Grand Cherokee cluster and build a new dash to fit in the YJ... That could be interesting...
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