Quick question about factory tach

[Keckdl]

My awesome wife bought me the factory reproduction tach from LMC for my birthday and I'm trying to find info before I install it. I have an 83 K10 Scottsdale with all the gauges and warning lights but no tach. I know I will have to get a new circuit board for the back, but will the tach fit in the old fuel gauge hole, and the new fuel gauge fit in the clock hole without modifying it?
If so does anyone make the or sell NOS instrument trays?

Thanks,
Dan
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[Sterling]

Did you get the small fuel gauge for trucks with factory tach? I'm pretty sure they fit right up. GM is all about cost cuts, 2 instrument trays is not GM like.

Does your new tach have 3 posts sticking out the back? The fuel gauge is 3 posts, one hot, one ground, and 1 for the sender feed. So if yours is 3 posts too, I bet the new circuit makes the sender feed into tach feed, so it should slip right in!

Best of luck with the set up! Also check your distributor where the ignition wires come out the side of the top. One of the posts is labeled TACH, if there is no wire going to that post, you will need to run a TACH wire to your dash circuit or however you wire this up.

[J Knight]

The tach you got from LMC is a replacement tach for a tach cluster and not designed to work with your standard gauge cluster housing. It will take some considerable modifications to your cluster housing, a printed curcit, a tach harness, and repinning of your cluster plug for everything to work.

[Keckdl]

Originally Posted by Sterling

Did you get the small fuel gauge for trucks with factory tach? I'm pretty sure they fit right up. GM is all about cost cuts, 2 instrument trays is not GM like.

Does your new tach have 3 posts sticking out the back? The fuel gauge is 3 posts, one hot, one ground, and 1 for the sender feed. So if yours is 3 posts too, I bet the new circuit makes the sender feed into tach feed, so it should slip right in!

Best of luck with the set up! Also check your distributor where the ignition wires come out the side of the top. One of the posts is labeled TACH, if there is no wire going to that post, you will need to run a TACH wire to your dash circuit or however you wire this up.

I did get the smaller fuel gauge and my tach does have three posts like the fuel gauge.
I also agree on the two styles of inst trays.

Dan

[Keckdl]

Originally Posted by J Knight

The tach you got from LMC is a replacement tach for a tach cluster and not designed to work with your standard gauge cluster housing. It will take some considerable modifications to your cluster housing, a printed curcit, a tach harness, and repinning of your cluster plug for everything to work.

I fully understand the wiring modifications for the swap, and that part really isn't a huge concern to me. You did say cosiderable housing modifications, and that does. Have you done this? Is the modification for the tach or for the smaller fuel gauge? Is it more than just drilling holes for the new gauges?

Thanks,
Dan

[J Knight]

Originally Posted by Keckdl

I fully understand the wiring modifications for the swap, and that part really isn't a huge concern to me. You did say cosiderable housing modifications, and that does. Have you done this? Is the modification for the tach or for the smaller fuel gauge? Is it more than just drilling holes for the new gauges?

Thanks,
Dan

I cant find it but there is a thread here where a member had to graft/glue the fuel gauge area of the tach cluster to a standard cluster to mount the little fuel gauge. To mount the tach in a standard cluster I think you just have to cut a 1in square hole in the back of the standard cluster. Also the tach is wired independent of the cluster curcit. Im sure there are some guys that have done this and can confirm it.
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[motornut]

there are some people adding a tach with fuel gauge
but as a seperate small one,it's over with the other gauges
cept when air/vac/clock
I went from idiots to tach gauges
without the right case your gona have to cut it/to fit through the back
don't use the fuel conections they don't line up
factory, the tach wired throught the firewall
when i did mine I wired the tach power to the rest of the cluster power
crimp on connetors will fit
had to add a ground for the small gas gauge...but no more big bouncy gauge

[Keckdl]

Originally Posted by motornut

there are some people adding a tach with fuel gauge
but as a seperate small one,it's over with the other gauges
cept when air/vac/clock
I went from idiots to tach gauges
without the right case your gona have to cut it/to fit through the back
don't use the fuel conections they don't line up
factory, the tach wired throught the firewall
when i did mine I wired the tach power to the rest of the cluster power
crimp on connetors will fit
had to add a ground for the small gas gauge...but no more big bouncy gauge

Thanks for the pic's. I actually read your post this morning and it was very informative, thank you.

Im a little confused about what you said about the small gauges, will I need to modify the hole more than just drilling the post holes when I replace my clock with the small fuel gauge?

[motornut]

Originally Posted by Keckdl

Thanks for the pic's. I actually read your post this morning and it was very informative, thank you.

Im a little confused about what you said about the small gauges, will I need to modify the hole more than just drilling the post holes when I replace my clock with the small fuel gauge?

not sure but seems the gauge bolts right in,from what Ive read

[Keckdl]

Originally Posted by motornut

not sure but seems the gauge bolts right in,from what Ive read

I'm just gonna order the circuit board and give it a shot when it comes in. I will post pictures as I go when I do. Thanks all for the insight.
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[ray_mcavoy]

Hi Dan,

You'll definitely have to do some modifications to the plastic cluster housing to make a factory/reproduction tach and the associated smaller fuel gauge fit.

Here is a pic showing a gauge cluster housing and a gauge/tach cluster housing. They're older housings for a mechanical oil gauge but will still give you an idea of the differences in the tach and fuel gauge areas:



The dingy/dirty looking housing is from a regular gauge cluster and the clean white one (painted with Krylon Fusion plastic paint) is from a tach/gauge cluster.

Over on the tach side it looks as though you can simply cut the big opening and screw the tach right in. The mounting points are already there.

But over in the lower left corner is going to be a bit more involved. You'll have to cut away the baffle that used to be for the "BRAKE" light and probably graft in the chunk of plastic with the 3 little square holes for the gas gauge terminals that you cut from the other side. The small gas gauge shares it's lower/right mounting screw with the neighboring temp gauge. But the non-tach cluster doesn't have a place for the screw that holds the upper/left corner of the small gas gauge so you'll probably have to make something there.

Now, if your existing cluster has a clock (instead of a "BRAKE" light) down in that lower/left corner it might make it easier to fit the small gas gauge in there but I don't know for sure.

[Keckdl]

Originally Posted by ray_mcavoy

Now, if your existing cluster has a clock (instead of a "BRAKE" light) down in that lower/left corner it might make it easier to fit the small gas gauge in there but I don't know for sure.

Great pic thanks. I do have the clock and it looks like the tach cluster's bottom left, if memory serves me right. Thanks again for the pic, that is exactly what I was looking for.