Tach/fuel combo gauge -- install, review, pics

[rich weyand]

I have dual tanks. I did not like the idea of switching the gauges with the fuel tank selector. Seems like a recipe for running out of gas to me. (For you aviation buffs, cf. Stinson Station Wagon.)

So I mounted a second fuel gauge in the empty position. This position would take the clock, or, if you got a tach, it would take a small fuel gauge instead of the big honking one next to the speedometer. So, there's a small fuel gauge made that fits into that position, and with a little work, you can put a second fuel gauge there, which I did. Two tanks, two gauges. Perfect.

Having a tach would be nice, though. So when I heard about the combination tach/fuel gauge from the larger trucks that used the C/K cab, that was cool. Sure, it went into a different basket, but the basket could be modded, just like I modded the basket to take the small fuel gauge in the empty position.

Even better was when I heard about a tach/fuel combo gauge that fit directly into the stock C/K basket. I installed it yesterday. Total elapsed time: 5-1/2 hours. Results: Excellent.

The dashboard was disassembled in the usual fashion, with all the usual hassles. Getting the headlight knob-and-stick out was annoying. The radio removal from the one-DIN shell was easy, removing the instrument bezel with the one-DIN shell installed was a pain. Removal of the other items necessary to remove the instrument basket was straightforward.

The instrument basket has to be modified to fir the new gauge. The fuel gauge mechanism fits where the shrouds for the "fasten your seat belt" and "brake" warning lights go, so the center part of the shrouds have to be cut out of the basket. After removing the warning light bulbs, a little work with a Dremel tool accomplished this. The divider between the two warning light shrouds has to be shaved right down to the bottom wall of the basket. Also, the bosses that hold the locating pins on either side of the shrouds have to be shaved down a touch.

The gauge sits so deep in the basket that the three pins that make the fuel gauge connections go right through the spring clip holes and stick out the other side. The spring clips are too tall inside the basket to let the gauge fit all the way down where it needs to be. I removed the spring clips and bent the upper portion of the spring clips (the parts that flare back out) out horizontally. I reinstalled the clips, fit the gauge into the basket, and fastened the gauge into the basket with nuts on the three terminal bolts.

The gauge mounting tabs have some flash or something on them that gives them an L or U cross-section, like a flange along the side(s) of the tabs. See picture. These must be removed for the gauge mask and lens to mount flush in their original position. I clipped them off with side cutters.

To restore a brake warning light, I cut the warning light lenses and created a new lens for the speedometer warning light locations from the pieces. The warning light lenses have the legends, plus a dark wide bar between positions: 4WD LOCK|CHOKE and FASTEN SEAT BELTS|BRAKE. I cut them with scissors along one side of the heavy dividing line so I had 4WDLOCK| and |BRAKE. I then overlay the heavy line of one over the heavy line of the other and secured with plastic styrene cement, so I had 4WD LOCK|BRAKE. You also need to cut a locating pin hole in the CHOKE side, because the locating pins are in different locations so you don't put the lenses in on the wrong side.

To get the BRAKE warning light to work, I removed the BRAKE warning light socket and the CHOKE warning light socket. Looking at the circuit board, you will see that these two lamps have one terminal in common already, the ignition trace. I soldered a small wire from the back side of the contact ear on one socket to the back side of the contact ear on the other socket, and replaced both sockets in the panel so the connected ears were in contact with the non-common terminals of those two positions. Basically, I bridged the two warning light positions to each other.

I then removed the FASTEN SEAT BELTS warning light socket and ran the tach wire out the back side of the basket through this hole.

Re-installation of the dashboard was straightforward and typically annoying.

I did not connect the provided wire directly to the distributor TACH connection. Instead I ran a new wire (had some per spec BROWN wire in stock) for the distributor connection so that I could have some service loop and a disconnect behind the dash. One crimp female for the distributor connection, and a male-female crimp disconnect set for the connection of my new wire to the provided wire behind the dash. I ran the wire from the distributor along the harness and then through the grommet that passes the speedometer cable. I left enough on each wire to do the crimp connection below the dashboard and tucked the extra wire up behind the dash.

To check tachometer function, I read the engine speed on idle with the timing light's rpm function and compared it to the tach reading. The tach is dead on as delivered. The new fuel gauge also gave the same reading (it was on about 1/4 tank when I did the install) as the old gauge did.

Here is the gauge side view. Note fuel gauge mechanism location; this is what requires removing the warning light shrouds. Note also the flange on one of the mounting tabs seen here. They all have some rubbery/plasticy flash on them that needs to be removed. The three mounting tabs must be simple metal tabs sticking out from the gauge, nothing more, either in thickness or in flange-like flash along the edges.

Before.

After.

(on the phone with the internet provider because I am having trouble uploading pictures right now. Pictures soon, I just don't want this window to time out!)

[rich weyand]

Here is the gauge side view. Note fuel gauge mechanism location; this is what requires removing the warning light shrouds. Note also the flange on one of the mounting tabs seen here. They all have some rubbery/plasticy flash on them that needs to be removed. The three mounting tabs must be simple metal tabs sticking out from the gauge, nothing more, either in thickness or in flange-like flash along the edges.



Before.



After.

[rich weyand]

One last thing I forgot. This tach/fuel combo gauge is available from http://www.gmsports.com. My understanding is that they have this gauge built semi-custom for them, so it is not available anywhere else. Shipping was next day and billing against my card was correct.

This is the item.
http://www.gmsports.com/content/new-...and-gmc-trucks

[dragonball98312]

Lmc has them as well

[rich weyand]

Not the same. The RPM range on the LMC unit is set up for a diesel.

[Valleycreek]

Thanks for the write up. I really want to do this. I only wish the lettering was available in the older style to match the existing. Not a big deal. Thanks for the pictures.

[83GMCK2500]

Originally Posted by Valleycreek

Thanks for the write up. I really want to do this. I only wish the lettering was available in the older style to match the existing. Not a big deal. Thanks for the pictures.

You mean like the one pictured here? http://www.tachman.com/oldsun.htm

[rich weyand]

Originally Posted by 83GMCK2500

You mean like the one pictured here? http://www.tachman.com/oldsun.htm

The issue with that one is that it is out of the medium-duty trucks, and does not fit the C/K light-duty instrument basket. That makes it much more work to fit. This thread shows the differences. http://www.dieselplace.com/forum/63-...duty-tach.html

The gmsports.com tach/fuel combo plugs into the existing instrument basket in the light-duty trucks. You can see how they put a set of terminals for the fuel gauge on a piece of plexiglas in the correct location for the instrument basket fuel gauge connections, then wired those to the actual fuel gauge mechanism, in the side view pic above.

You can either use the gmsports.com gauge with the different font, or do more fitting work to get the classic font. I kind of like the bigger numerals on a tach, but it's a taste thing.

[Valleycreek]

The font is not a deal breaker by any means. I am probably going to do it, when my truck gets here. Thanks again for the write up.

[y5mgisi]

That is so bad ass. I have always thought about dual fuel gauges, but this is just crazy slick.

[rich weyand]

I like it a lot. Here's a note about how to mount the small fuel gauge in the clock position.

Getting the dummy plug out of the blank position is no problem. But there is a missing mounting boss for the fuel gauge in the "no-tach" instrument basket. What I did was to get a plastic spacer (sometimes called a standoff) that was internally threaded #6-32, and one that was not threaded but had a #6 clearance hole through the center. The back of the instrument basket is not square with the instrument faces at that point, and the side of the basket angles in so that you can't just mount a boss straight back from the gauge mounting tab. So I cut a piece of the clearance hole spacer at an angle, then drilled a hole in the instrument basket and put a #6-32 machine screw through the instrument basket, through the clearance hole spacer, and into the threaded spacer. I made this angled piece long enough to put the end of the threaded spacer in the right place for the gauge mounting tab, and I rotated it around until it angled the threaded spacer to the right position. Get more than one clearance spacer, because it could take you a couple tries to get the length and angle right. Then I tightened down the machine screw, fixing the spacers to the instrument basket. Voila! A boss for mounting the small fuel gauge. Just use a short #6-32 machine screw into the end of the threaded spacer as the mounting screw for that gauge mounting tab.

For wiring, I knew the other gauge had the right power and ground connections, so I took two pieces of wire and put a small crimp-on eye terminal on both ends of each, and wired the small gauge + and GND terminals to those of the one in the stock position with nuts on the back of both gauges' screw terminals. This still works with the tach fuel combo because that unit plugs right into the stock wiring. Note that both gauges need the resistor across the back.

For the sender wires, I connected the passenger side tank sender wire to the stock sender wire to the stock gauge so it would be on the right side gauge. I ran a separate sender wire from the driver's side tank sender across the back of the cab and followed the stock sender wire up the vehicle and into the cab. I wired it to the small fuel gauge, leaving a little extra wire behind the dash and using a male-female crimp-on disconnect pair behind the basket so I could disconnect it to get the basket out.

And that was about it. The hard part was making up for the missing boss, but some threaded spacer, a clearance spacer, and some playing around did the trick.

[jb3t]

Awesome write up.

[73kay]

I bought the tach and when
I called the guy up he had the older style fonts available for the tach. Easy install. I love it. Still haven't added a small gas guage to the bottom left cavity but it was worth the money Imo.

[Titomars]

Thanks for the write Rich. interesting idea about the dual fuel gauges I have a factory tach dash and dual tanks. I just want a factory tach that goes past 5k. my 454 will be seeing it's true redline of 6k+ once I get inside it and make some changes.

[wilkin250r]

On the topic of fonts and matching the "old style" with the "new style", are the speedometers interchangeable? If the tach has the "new font", could I just swap in a "new font" speedometer and match that way? Or are there other differences in the speedometer that make this impossible?

[hatzie]

VDO makes a Cockpit series 52mm 90Ω dual fuel tank gauge.
Not stock looking but if you're doing the 6 gauge Autometer type conversion you could just use VDO instead.
You could also put it in the AC vent or one of the pillar pods Chris has finalized.


http://www.howardinstruments.com.au/...ction-2013.pdf

[rich weyand]

Originally Posted by wilkin250r

On the topic of fonts and matching the "old style" with the "new style", are the speedometers interchangeable? If the tach has the "new font", could I just swap in a "new font" speedometer and match that way? Or are there other differences in the speedometer that make this impossible?

I believe you can ask gmsports.com for the old fonts. I did not know this at the time, though I would probably have gone that way had I known. No biggie to me either way.

[motornut]

Originally Posted by wilkin250r

On the topic of fonts and matching the "old style" with the "new style", are the speedometers interchangeable? If the tach has the "new font", could I just swap in a "new font" speedometer and match that way? Or are there other differences in the speedometer that make this impossible?

the back speedo clip does change postion,I tried ...I wasn't gona cut stuff
79 and 88 shown.

[Marshy]

Subscribed.... I am dying for a tach and want to keep it stock looking. I will have to come back and read this over thoroughly.

[Factory Guy]

Unfortunately the tach /fuel gauge is no longer available at http://www.gmsports.com.

It says page not found.

[Palf70Step]

Very nice idea. Thanks for all the notes and writeup.

[CarolinaHD]

Originally Posted by Factory Guy

Unfortunately the tach /fuel gauge is no longer available at http://www.gmsports.com.

It says page not found.

That's correct, I was told the man that was making them died unexpectedly and he never taught anyone else how to make them..

Glad I got mine when I did

[Hart_Rod]

Originally Posted by CarolinaHD

That's correct, I was told the man that was making them died unexpectedly and he never taught anyone else how to make them..

Glad I got mine when I did

That's a bummer on both fronts...🙁