diesel tachometer

[joeq]

Not sure where to post this question, so hopefully this forum will do.
I was curious about up-grading my current dash layout, to include a tach. Currently there's a large fuel gauge to the right of the speedo. And in the LHS pods, there's an M/T spot lower left. I've seen the layouts with the large tach next to the speedo, and the small fuel gauge in the lower LHS. My question is the wiring. Is there connectors incorporated in the harness to do this, or does it have to be fabbed? I've gone back a few pages here, and can't find any info on this. I'm sure it's probably been brought up in the past. Thanx.
(83 C-30, 6.2, dual tanks)

[Dvldog8793]

Never seen a factory tach in the older 6.2 trucks....lots of gassers had them but I have never seen a diesel.

I have a Tiny-tach in my van that works good and is VERY simple to hook up. DOES not look factory at all but functions very good.

I have an ISSPro in my blazer that was small enough to mount in the open gauge hole to the left of steering column. I looks nice and functions like a regular gauge.

Hope this helps...
Good luck

[joeq]

thanx Dog. Wonder if there's a way to get the factory tach to work on a diesel? I've heard they work off the alternator some how. Have to look into it.

[trbankii]

Not sure about a factory tach, but Autometer offers these: https://www.youtube.com/watch?v=HhLPAPZxNsM

I also know that there is quite a bit of information out there for converting a gas VW tach to work on a diesel VW engine, such as this: http://www.4crawler.com/Diesel/Cheap...er/index.shtml

You could probably do the same for a gas tach of similar vintage for your C30, but I have no idea how hard it would be to figure out.

[joeq]

Interesting design how the sensor works on the Autometer tach. I'm thinkin there's a better way of attachment than a large worm clamp. I'll have to read up on the VW info. I'ld sure like to make the factory tach work. I have my shop manual, with the electrical schematics, and none of it mentions a tach.
I'm sure there must've been an option on one of the years with the 6.2.

[AKMark]

Never seen a 6.2 with a factory Tach

[joeq]

Bummer.

[ginger743]

If the 6.5 Tach is driven off of the alternator , get a 6.5 alternator and Tach at a junk yard and it seems you'd be all set. May be a problem however with pulley size , " rpm " etc.

Jerry

[DmaxMaverick]

It's more simple than that. Use a gasser tach (the red-line will be off, but that's what it is), gasser small gage, and a vacuum pump with the pulse generator. Using the alternator as a pulse source will be complicated, as there isn't one that will fit.

[joeq]

If the 6.5 Tach is driven off of the alternator , get a 6.5 alternator and Tach at a junk yard and it seems you'd be all set. May be a problem however with pulley size , " rpm " etc.

Jerry

there's an idea. Will the 6.5 tach mount to the earlier dash/wiring? Is the face color the same? Another possibility to investigate. thanx.

[joeq]

It's more simple than that. Use a gasser tach (the red-line will be off, but that's what it is), gasser small gage, and a vacuum pump with the pulse generator. Using the alternator as a pulse source will be complicated, as there isn't one that will fit.

I have a vacuum pump that does nothing more than drive the oil pump, but doesn't have any generator on it Gregg. This one is a little over my head. I do like the idea of the higher red-line. Seeing I'll be able to spin the 6.2 faster with that tach, I might as well put hedders on it.

[DmaxMaverick]

I have a vacuum pump that does nothing more than drive the oil pump, but doesn't have any generator on it Gregg. This one is a little over my head. I do like the idea of the higher red-line. Seeing I'll be able to spin the 6.2 faster with that tach, I might as well put hedders on it.

Never thought of it that way. I don't recommend it, however. I've had one get away from me for too long. I must have hit 5,500 RPM's before getting it shut down. NOT an experience I'd prefer to repeat! The engine survived, but I had doubts about me and the shop for a few seconds (of eternity).

The vacuum pump I mentioned is the same as yours, except it has a connector on it for the tach lead. I'll look around for one, or find a link so you can see it.

The 6.5 tachs are very different. I don't think they are similar size, and they certainly have a different appearance. It might look about as good as a tach duct-taped to the column by the time you're done with it.

The 6.5 alternators are very different from yours. They are designed to be used with a serpentine belt drive, and are stationary (no adjustable mount). You may be able to have yours, or a new/rebuilt alternator modified for tach use.

Either way will require a frequency buffer. The engine/cam driven is simple, 8 pulses per rev, I think. The alternator method would be a bit sketchy, at best, with estimated rational diameters of the pulleys, plus the diameter variation inherent to V-belt pulleys, / the pulse frequency of the alternator.

I think you'd be much better off using a crank sensor (swap in a 6.5 timing cover, add CKP, buffer). Another member here posted up good data on the CKP he was using for an electronic tranny controller. Somewhere in this same forum, IIRC, 6 or 8 months ago.

[DmaxMaverick]

Here it is:

Tach signal from crank position sensor

[joeq]

You know, this is so puzzling to me, that this dilemma hasn't been rectified. Because a diesel truck usually is considered a "work horse", and a tach is more pertinent to such a vehicle, than a speedo, (well, almost), and there are so many of these vehicles sold, you would've thought this wouldn't even be an issue. Especially, of all vehicles, a CHEVY. Everything is first introduced on a Chevy.
I've not only gathered info from this site, but searched other areas also, and altho there are lots of "potential" installations of factory tachs installed in 80s diesel trucks, none of them were completed successfully. I see aftermarket ones working, and computer controlled 6.5s, but as of yet, don't see any square bodied factory installs. My brother has worked with GMCs for 35 years, and even he had a hard time giving me info. Last nite we did find a Sierra package offered in later 80s with a factory tach, running off the alternator, but it appears to be as rare as 69 Trans Am convertible.
From what I've gathered so far, from everyones posts, is there are many different ways to pick up a signal. From the back of the alternator, to a crank trigger, and also a vacuum pump. But even if this signal materialized, if the ribbon cable going to the back of the factory gauge isn't compatable, it appears there would be no way to connect it. Unless there were an available pin/wire combo in the harness, that could be jumpered to the back of the tach.
Currently, my existing dash layout consists of the big fuel gauge to the right of the speedo, and an empty pod on the lower left under the voltmeter. My dream would be to relocate the fuel gauge to the lower left pod, and have the factory tach, next to the speedo. Seems at this point, if I want the tach, I'll have to purchase a small aftermarket one, and put it in the lower left pod.
P.S. What about the top kicks, or C-40s or 50s. Is there any potential there? They must've had 6.2s with tachs. Are their dash layouts any different?

[Yukon6.2]

Hi
I have the small isspro tach.I got a single gauge pod and mounted it on my steering column.My truck is a 90 so there is a protrusion from the column for the blinker stick.Mine is mounted on that,it doesn't cover any other gauges or lights.Been using it for 8-9 yrs no problems.
Thomas

[Joseph~]

FWIW Review Clark Brothers Instrument Company

http://www.clarkbrothers.net/G_military.html

Catalogs
http://www.clarkbrothers.net/catalogs.html

I think this is going to be very expensive!

Regards

Joseph

[trbankii]

I've always thought it was a bit odd that instrumentation tends to increase with trim level. The base model in many vehicles gets you a speedometer, fuel gauge, temperature gauge, and a bunch of idiot lights. The "double ultra limited" model gets you the full zoot gauge package.

Further irony is that I tend to find that the person buying the top of the line model is less likely to actually use any of the gauges other than the speedometer and gas gauge - and sometimes don't pay much attention to those either...

[joeq]

Hi
I have the small isspro tach.I got a single gauge pod and mounted it on my steering column.My truck is a 90 so there is a protrusion from the column for the blinker stick.Mine is mounted on that,it doesn't cover any other gauges or lights.Been using it for 8-9 yrs no problems.
Thomas

Checked out the site, and of course there's no pic of the 2" diesel tach.

[joeq]

FWIW Review Clark Brothers Instrument Company

http://www.clarkbrothers.net/G_military.html

Catalogs
http://www.clarkbrothers.net/catalogs.html

I think this is going to be very expensive!

Regards

Joseph

Man their deluxe gauge package looks all business. Nice. (Afraid to look at the prices.)

[joeq]

Further irony is that I tend to find that the person buying the top of the line model is less likely to actually use any of the gauges other than the speedometer and gas gauge - and sometimes don't pay much attention to those either...

I concur 100%.