Tach install

[BADAZ chevy guy]

I want to ad a tach to my dash. 1977 C10. I have the large fuel gauge now. Will I need to replace the printed circuit? And where do I put a fuel gauge?

[rich weyand]

Check this out. I think you can patch in the wiring on that end.
http://67-72chevytrucks.com/vboard/s...6&postcount=16

[BADAZ chevy guy]

So, the fuel gauge is part of the tach gauge. Is that the way they all come?
What year/make can I find a gauge in? I can't really afford new.

[rich weyand]

No, if you got a tach, the fuel gauge went where you have the clock. You couldn't have both the tach and the clock. The combo gauge was off of the 2-1/2 ton trucks that used C/K cabs.

[ray_mcavoy]

Like Rich said, those tachometers with the small fuel gauge in the bottom were originally used in medium duty trucks. And will allow you to put together a cluster with both a tach & clock.

The tach clusters used in 1/2 to 1-ton pickup trucks look like this:


They have their own special cluster housing and printed circuit that re-locates the fuel gauge to the lower left corner (where your clock is now).

Be aware that there were several different versions used over the years:

1973 - 1975 use an ammeter ... NOT a direct plug-in into 76+ trucks with a voltmeter.
1976 uses a voltmeter and mechanical oil gauge. One of these would plug into your '77 but there will be some minor differences with the "brake" and "fasten belts" lights at the bottoms of the speedometer & tach.
1977 (and late '76) also use a voltmeter and mechanical oil gauge. The example photo I posted above is a '77 cluster. One of these would be a direct plug-in swap into your '77 since it's already wired for a gauge cluster. The tach wiring is in a separate harness.
1978+ use a voltmeter and electric oil gauge. One of these could work in your '77. But the wiring pin-out changed in '78 so you'd have to re-pin the cluster connector and add an oil pressure sender & wire.

[rich weyand]

If you find the combo tach/fuel gauge used, here's how you do the install.
http://www.dieselplace.com/forum/63-...duty-tach.html

[mattcrp1]

Try this, its not exactly a truck one but still looks good.

http://67-72chevytrucks.com/vboard/s...=276995&page=7

[1774btcrew]

Originally Posted by ray_mcavoy

Like Rich said, those tachometers with the small fuel gauge in the bottom were originally used in medium duty trucks. And will allow you to put together a cluster with both a tach & clock.

The tach clusters used in 1/2 to 1-ton pickup trucks look like this:


They have their own special cluster housing and printed circuit that re-locates the fuel gauge to the lower left corner (where your clock is now).

Be aware that there were several different versions used over the years:

1973 - 1975 use an ammeter ... NOT a direct plug-in into 76+ trucks with a voltmeter.
1976 uses a voltmeter and mechanical oil gauge. One of these would plug into your '77 but there will be some minor differences with the "brake" and "fasten belts" lights at the bottoms of the speedometer & tach.
1977 (and late '76) also use a voltmeter and mechanical oil gauge. The example photo I posted above is a '77 cluster. One of these would be a direct plug-in swap into your '77 since it's already wired for a gauge cluster. The tach wiring is in a separate harness.
1978+ use a voltmeter and electric oil gauge. One of these could work in your '77. But the wiring pin-out changed in '78 so you'd have to re-pin the cluster connector and add an oil pressure sender & wire.

Ray, it never ceases to amaze me the knowledge you have on the wiring on these trucks. While this isn't my question, I appreciate all of the help that you have given me with my wiring questions!

[motornut]

different but I converted my 78 from idiots to tach/gauges
even from lights to gauges a location changed
I got lucky and found one second hand,was complete too
the tach has a cluster section of it's own back there to connect to the cluster,plus wires
the circut board for the tach cluster is different,no big gas area
I reused the stock engine wires and just repinned the plug or it would have burnt it.

[BADAZ chevy guy]

Originally Posted by ray_mcavoy

Like Rich said, those tachometers with the small fuel gauge in the bottom were originally used in medium duty trucks. And will allow you to put together a cluster with both a tach & clock.

The tach clusters used in 1/2 to 1-ton pickup trucks look like this:


They have their own special cluster housing and printed circuit that re-locates the fuel gauge to the lower left corner (where your clock is now).

Be aware that there were several different versions used over the years:

1973 - 1975 use an ammeter ... NOT a direct plug-in into 76+ trucks with a voltmeter.
1976 uses a voltmeter and mechanical oil gauge. One of these would plug into your '77 but there will be some minor differences with the "brake" and "fasten belts" lights at the bottoms of the speedometer & tach.
1977 (and late '76) also use a voltmeter and mechanical oil gauge. The example photo I posted above is a '77 cluster. One of these would be a direct plug-in swap into your '77 since it's already wired for a gauge cluster. The tach wiring is in a separate harness.
1978+ use a voltmeter and electric oil gauge. One of these could work in your '77. But the wiring pin-out changed in '78 so you'd have to re-pin the cluster connector and add an oil pressure sender & wire.

That's just the info I was looking for. Thank you. Now I just need to find one. Wish me luck! lol

[rich weyand]

BTW, if you find one from the medium duty truck, there is some jury-rigging to do to get it hooked up because the clips for the fuel gauge were in the lower position. That is, they used a different instrument basket, so you will have to mod yours. There is a product from gmsports (http://www.gmsports.com/content/new-...and-gmc-trucks) that is a reproduction that includes the fuel gauge pins in the correct position for the stock C/K instrument basket, so no such mods are necessary. They commission this product, so it is not available from anyone else. All you need is to plug the gauge into the existing basket, run the supplied tach wire to the distributor, and you're done.

[BADAZ chevy guy]

Originally Posted by rich weyand

BTW, if you find one from the medium duty truck, there is some jury-rigging to do to get it hooked up because the clips for the fuel gauge were in the lower position. That is, they used a different instrument basket, so you will have to mod yours. There is a product from gmsports (http://www.gmsports.com/content/new-...and-gmc-trucks) that is a reproduction that includes the fuel gauge pins in the correct position for the stock C/K instrument basket, so no such mods are necessary. They commission this product, so it is not available from anyone else. All you need is to plug the gauge into the existing basket, run the supplied tach wire to the distributor, and you're done.

I have looked into this gauge before. I like the idea of not having to change printed circute, but I'd rather find an OEM cluster if at all possible.

[jcwoodworks]

So I have the same issue and I want to clarify this:

I currently have a 77 with the Volt, Mechanical Oil, temp, Speedo and Large Fuel gauge. The lower left small gauge spot is blank.

I want to put in a 77 (or 76) set with Volt, Mechanical Oil, temp speedo, large tach and small fuel gauge where the blank is currently.

If I find a used one, it should be plug and play, with the exception of wiring in tach which has a separate harness. Is this correct?

OR

If I find an old back cluster mount for the 77 with the positions I want....I could then buy a new printed circuit board and new instruments and it would be plug and play. Is this correct?

Any help would be greatly appreciated.

[ray_mcavoy]

Originally Posted by jcwoodworks

So I have the same issue and I want to clarify this:

I currently have a 77 with the Volt, Mechanical Oil, temp, Speedo and Large Fuel gauge. The lower left small gauge spot is blank.

I want to put in a 77 (or 76) set with Volt, Mechanical Oil, temp speedo, large tach and small fuel gauge where the blank is currently.

If I find a used one, it should be plug and play, with the exception of wiring in tach which has a separate harness. Is this correct?

That is correct. Since your 77 is already wired for the factory gauge cluster, a 77 tach cluster will be a direct plug-in swap with no need to re-pin the cluster plug. An early/mid 76 tach cluster will work too ... they have some minor differences with the "brake" and "fasten belts" lights but making one work in your 77 would only involve re-locating a couple wires on the plug.

In general, re-pinning the cluster plug and/or making changes to the wiring is usually only necessary when starting off with a truck that was originally wired for idiot lights. Or when swapping in a cluster from a different year range that involves dealing with ammeter vs. voltmeter and/or mechanical vs. electric oil gauge differences.

Originally Posted by jcwoodworks

OR

If I find an old back cluster mount for the 77 with the positions I want....I could then buy a new printed circuit board and new instruments and it would be plug and play. Is this correct?

Yes, that is also correct as long as you use a 77 printed circuit. And the only instruments you'd have to buy would be the tach and small fuel gauge. Everything else could be swapped over from your existing gauge cluster.

[jcwoodworks]

Ray thanks so much for your help! I am having a hard time finding this cluster or even the mounting for the instruments. Here are pics on one I have found, but it has the AMP meter, not the VOLT. Can I use this one if I change out the AMP to VOLT and use a new printed circuit or is the back the AMP and VOLT area different on the back?

[jcwoodworks]

Here is the back

[jcwoodworks]

Hopefully this one is bigger

[jcwoodworks]

Also mine is a 4 speed manual shift on the floor. Can I just remove the automatic cluster?

[ray_mcavoy]

Originally Posted by jcwoodworks

Ray thanks so much for your help! I am having a hard time finding this cluster or even the mounting for the instruments. Here are pics on one I have found, but it has the AMP meter, not the VOLT. Can I use this one if I change out the AMP to VOLT and use a new printed circuit or is the back the AMP and VOLT area different on the back?

You're welcome.

Yeah, the 76 & 77 specific tach clusters do seem to be a bit harder to locate than the 73-75 and 78+ versions.

Yes, you could remove the ammeter from a 73-75 cluster and replace it with a voltmeter. And change out the printed circuit on the back to make it compatible with your 77. I think the voltmeter will screw directly into the old ammeter spot and the only modification you'd have to make would be to cut a small square hole in the back of the plastic housing to line up with one of the terminals that's in a different spot on the voltmeter vs. ammeter.

However, there are a couple of other issues to consider with a 73-75 tach cluster:

(1) I'm not sure how concerned you are with year-correct appearance, but there are some cosmetic differences. Most noticeable is the lack of a semi-circular line inside the tick marks on the 73-75 speedometer & tach. Also, the 73-75 tach face doesn't have a "window" at the bottom for additional indicator lights.

(2) The circuitry in the 73-75 tachs is non-serviceable because the components are encapsulated in an epoxy type material. Repairing a non-working 73-75 tach could get expensive because the entire control circuit board would have to be replaced.

Originally Posted by jcwoodworks

Also mine is a 4 speed manual shift on the floor. Can I just remove the automatic cluster?

Yes, just take out 2 screws to remove the auto trans shift indicator.

[jcwoodworks]

Thanks again Ray. I was planning on getting this cluster on ebay to use only the housing. Then I was going to get a new printed circuit and all new gauges and make it look like new. I'm not to worried about the keeping everything the correct year. Mine has a 350 GM crate with a new MSD ignition. Would this be considered and HEI, so I get the correct harness for the new tach? Also any suggestions for taking out the contacts out of the old cluster without wrecking them?

[motornut]

from the inside push one side into the hole then the other side

[ray_mcavoy]

Originally Posted by jcwoodworks

Thanks again Ray. I was planning on getting this cluster on ebay to use only the housing. Then I was going to get a new printed circuit and all new gauges and make it look like new.

You're welcome again

In that case, the housing from that cluster should work just fine for what you are planning. About the only other difference I can think of would be in the baffles that surround the indicator light areas at the bottoms of the speedometer & tach. But those differences won't be an issue unless you want to retain all of the lights (4 wheel drive, brake, and fasten belts) that would normally be in those locations for a 77.

Originally Posted by jcwoodworks

Mine has a 350 GM crate with a new MSD ignition. Would this be considered and HEI, so I get the correct harness for the new tach?

Your MSD ignition would not be considered either "points" or "HEI" as far as the tach hookup is concerned. With the MSD, I believe you need to connect the tach to the box's "tach output" connection ... not to the coil.

The only difference between a points vs. HEI tach harness is the connector on the end that hooks to the coil. I think the HEI style would be easier to adapt ... you could make a jumper wire with the appropriate terminals on each end that would connect from the MSD box to the connector on the HEI harness.

Originally Posted by jcwoodworks

Also any suggestions for taking out the contacts out of the old cluster without wrecking them?

Ditto what motornut just posted ... pushing them out one side at a time will get them out without damage.

[jcwoodworks]

Can you drill out holes for the indicator lights where the bulbs would go in the circuit? Or is this getting to be too much modification and maybe I should just keep looking for the correct housing?

[ray_mcavoy]

Originally Posted by jcwoodworks

Can you drill out holes for the indicator lights where the bulbs would go in the circuit? Or is this getting to be too much modification and maybe I should just keep looking for the correct housing?

Yes, you should be able to drill out the necessary holes without too much trouble. The holes aren't completely round ... they have notches on each side for the 1/4 turn bulb sockets to snap into. So they'd need a bit of additional work with a dremel tool, file, etc. to create those notches. Still shouldn't be all that difficult though.

The late 76 & up clusters that have provisions for the extra lights also have a divider baffle cast into the plastic between the two bulb holes. Adding those baffles shouldn't be all that much work either ... just cut some pieces of abs plastic to the appropriate size and glue them into place.


And while we're on the topic of modifying the plastic cluster housings, it probably wouldn't be a whole lot of work to start off with a regular gauge cluster housing and modify it to accept a factory tach & small fuel gauge.

For reference, here is a pic comparing the two:

These are both 77 cluster housings ... regular gauge cluster on the top and gauges w/tach on the bottom.

As you can see, the only difference on the right side is the large cut-out area behind the tach. The tach uses the same mounting screw locations as a large fuel gauge.

The left side would need a bit more work to accommodate the small fuel gauge. The round baffle from the old "brake" light would need to be cut away. Since the large & small fuel gauges have the same terminal pattern, the section of plastic (with the 3 square holes) that was cut from the right side could be saved, trimmed down, and glued into place behind the new fuel gauge location. Then a mounting stand-off would need to be added for the upper/left corner of the small fuel gauge.

[jcwoodworks]

I do have an extra gauge cluster so I think i will give that a try. A better idea would be for you to sell me the nice looking cluster housing on the bottom!! You have been a great help. Please let me know if you have any leads on the housing I need.