73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Interior & Equipment => Instrumentation => Topic started by: Sprinkler-Man on March 16, 2014, 10:02:51 AM
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My truck 80 GMC K1500 donor truck 79 Chevy 1500.
The donor truck came with a factory tach setup that I would like to use in mine but my truck did not come with a tach. What is involved in getting it to work?
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Well it's going to be fairly easy. There will be some small electrical work required but shouldn't be to hard. First off lets get some stuff figured out. Your truck has what gauges? Top left: voltmeter, top right: oil pressure, bottom right: coolant temp, bottom left: no gauge or a clock, middle left: speedometer, middle right: fuel level? Is this all correct?
Now I'm guessing with a tach the donor truck has the same setup. Except that the fuel gauge is moved down to the bottom left where the empty slot/clock is and the tach is now next to the speedometer. Correct?
Being that both trucks are late 70's, you should have an HEI distributor in your engine right?
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This Thread (http://forum.73-87chevytrucks.com/smforum/index.php?topic=9604.0) clearly states that a 78 - 80 would work, earlier has a different oil gauge.
This Thread (http://forum.73-87chevytrucks.com/smforum/index.php?topic=23623.msg223421#msg223421) is really helpful, pay attention to the last comment by CaptKoas, "IF you get the whole cluster from a 78-up for your 80 it will technically plug in. Verify the wires though." I also believe you need the printed circuit board to swap also as pointed out by Capt. in the same article toward the top of the same page.
Here are 2 pics showing 2 different places to put tach's. The big RPM gauge that is on the right of the speedometer, they actually sell an aftermarket one that has a fuel gauge built into it if you wanted to add a clock to the bottom left corner where the small gas gauge is in this picture.
( the pics are from the second thread by the way)
(https://lh5.googleusercontent.com/-ukBspvHAlUk/TrGlb1oMTiI/AAAAAAAAAAk/EJskoK08DY0/s640/DSC00614.JPG)
(http://www.unknownbrewer.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=16748&g2_serialNumber=2)
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Bake74. Your "Thread" in green is a link I'm guessing and it doesn't appear to be working. I tried clicking on it multiple times, unsuccessfully.
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His links worked for me.
Chris Lucas
73-87chevytrucks.com
captkaoscustoms.com
squarebody.biz
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Bake74. Your "Thread" in green is a link I'm guessing and it doesn't appear to be working. I tried clicking on it multiple times, unsuccessfully.
I just checked again and they are working for me also, I am no computer expert to tell you what to try and make it work on yours, sorry.
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Well it's going to be fairly easy. There will be some small electrical work required but shouldn't be to hard. First off lets get some stuff figured out. Your truck has what gauges? Top left: voltmeter, top right: oil pressure, bottom right: coolant temp, bottom left: no gauge or a clock, middle left: speedometer, middle right: fuel level? Is this all correct?
yes..thats correct
Now I'm guessing with a tach the donor truck has the same setup. Except that the fuel gauge is moved down to the bottom left where the empty slot/clock is and the tach is now next to the speedometer. Correct?
yes...correct
Being that both trucks are late 70's, you should have an HEI distributor in your engine right?
yes
I have the entire cluster but someone has told me that i may need the original connector also.
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Good. Now I would follow the link that Bake74 provided. Like he said you will need the printed circuit board, the reason being most of the circuits are the same, however they differ slightly because of the added tach and relocated fuel gauge. Also double check all your wires.
Now for the wiring. Because you don't have a factory tach you will need signal from the distributor. On the side of the cap were the plug is and the battery wire. There is an unused plug, it is labeled "tach" simply put a female spade connector on a wire and plug it into that empty slot. Now run that wire away from the engine and through the firewall. Under the dash, run the wire to the tach signal wire in the new plug for the new cluster. That will provide signal to the tach to show rpms.
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why would i need a circuit board if i am going to swap the entire cluster? The new one already has a circuit board.
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why would i need a circuit board if i am going to swap the entire cluster? The new one already has a circuit board.
The printed circuit board is usually considered a separate part, but if you are getting it with the new cluster you do not have to worry.
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Ditto on Bake. Only because it is removable and can be bought separately.
Now. Bake or someone could check me on this. The plug that goes into the printed circ board in Sprinkler Mans Chevy is set up for no tach. The GMC donor is tach. So, to make the signal for the gas gauge work properly, couldn't he remove the terminals for the gas gauge and reinstall them back in the plug were the new printed circuit would have gas gauge signal leading to the small gauge quad? Also, couldn't he just pull the connectors out of the donor plug for the tach and insert them into the now empty spaces on the original Chevy plug and just run the wires to his new wires for the tach signal, power ground and distributor signal?
This means he wouldn't really need the new plug, he just swaps some terminals around and puts in a few in the empty spaces. The plug already had empty spaces because it had no clock or 4th small gauge. So in easy words, move the fuel gauge wires of the plug to the empty slots for small gauges and put in new wires in plug for signal to tach.
Does this all make sense??? LOL Sprinkler Man, are you confused yet? 😜
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I have not done this swap yet, I plan on doing it and read a lot about it, but from the 2nd thread in my first post, CaptKoas said it is just a plug into new board and go, so taking him at his word (I know he has done it a couple of times), you should just need to plug it in and go.
Sprinkler-Man, please keep up updated on how and what you had to do to make it work.
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Yes LTZ C20, you are correct in your statements about not needing a new plug. To change from a non-tach cluster to a tach cluster, you DO need to re-pin the plug, even if the clusters are from the same year. Printed circuits are different between the cluster types also. Get an electrical schematic from both years and cross-reference all the wires you are dealing with. The printed circuit from the 79 "should" work with the 80, as long as you understand and get the wiring correct for the components you are dealing with.
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Ok sweet. That's what I thought.
There ya go Sprinkler Man, that should be everything you need. Just gotta re-pin the old plug.
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Wow...my head is spinning. It almost seems like it would be easier to put a after market tach where the clock would be. I really was hoping it would be more of a plug and play swap. I will keep you all posted on my progress.
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Um, that IS a plug and play: swapping the pins around is no big deal, and all the wiring diagrams are here on the site.
Oh. Buy the pin removal tool. It's worth it, compared to buggering one up.
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putting a Tach where the clock is will be much more work than verifying where electrical pins are and moving them if necessary.
The 1979 from 1980 won't have more than 5 to move if any...
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Yea that's as plug and play as you can get. Adding an aftermarket one is more work. Especially if you want it in the cluster. You will have to cut out sections of the cluster for it to fit, run more wiring then needed for the factory swap, provide power, ground, and backlight signal. Not to mention finding a gauge that you like and fits there.
Trust me, I have a aftermarket tach too, mounted to the steering column. It's ok for now and works but one day I'm getting a whole new cluster from Dakota Digital.
Trust us, you will be pretty happy with a cluster swap.
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Oh. Buy the pin removal tool. It's worth it, compared to buggering one up.
There is a tool for this? Please elaborate...
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Yes there is. There's different types for different plugs. However, I usually use a small screwdriver, like for eye glasses or small detail work, to remove the terminals from the plug. As long as you don't force it you won't damage anything.
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Oh. Buy the pin removal tool. It's worth it, compared to buggering one up.
There is a tool for this? Please elaborate...
You Tube has all kinds of video's on for these terminal release tools, some kits even cover a wide range of connectors.
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I used a small screwdriver when I did mine too. Worked just fine for me. This is just the first time I have ever heard anyone speak of a specific tool for our particular trucks.
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Update on the cluster swap. Everything went smoothly with the swap. The only thing I had to modify was the hot lead end from the tach harness to fit in the fuse box. I also ran the tach wiring out the same hole as the speedo cable by cutting a slit in the rubber fire wall grommet to let the wire fit in. I now have a cluster with a factory tach and couldn't be happier.
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Excellent. Thanks for following up.