tachometer

[Mv7fd]

I'm thinking about getting a factory tach and putting it in where the fuel gauge is now and getting the smaller factory fuel gauge and putting that where my non working clock is. is this worth doing or would it be easier and better to just get an aftermarket tach and if so where is a good place to put the after market tach

[mrolds88]

I would look for an assembly. If for no other reason that the printed circuit is different. The last square I had, had a Sun tach on the column in between the speedo and fuel guage.

[hatzie]

Get a complete unit.
73-75 Ammeter mechanical oil pressure Don't use on other years unless you like electrical fires. The 73-75 tachs are less than reliable and potted so the boards can't be repaired just replaced.
76 Volt meter and mechanical oil pressure
77-80 Volt Meter and Electric oil pressure. 100mph speedo dropped to 85mph sometime in this range.
81-89 larger tan font different color needles and mechanical speedo maybe 81-90?
90-91 electric speedo... Maybe only 1991?
Sometime in the 88-91 R/V squares there was a mechanical speedo with trip odometer.

The medium duty 40-60 trucks have tachs with fuel gauges on the bottom so you could put a clock in the lower left corner hole.

Be sure to get a V8 or I6/V6 tach whichever you have... and be sure to avoid the MD diesel tachs.

[johnwaynejeep]

Originally Posted by hatzie

Get a complete unit.
73-75 Ammeter mechanical oil pressure Don't use on other years unless you like electrical fires.

Hatzie,

I'm putting a dash cluster in my 74 that I sourced from a mid 80s. I wanted to ask you about the dash fire issue you mentioned. I sent you a PM so I'm not hijacking this post. thank you Sir

[86wrangler]

Someone read my mind yesterday, WOW! Was just strolling through the aisle looking at tachs and was gonna ask the same thing, Id like to leave my 77 as factory looking as i can as its sierra classic. (no sun tach) updated pics please

[rich weyand]

This is what I did.
http://forum.73-87chevytrucks.com/sm...8352#msg238352

[johnwaynejeep]

Mv7fd,

I noticed that GM had a tendancy to cut holes in the backplane printed circuit board for items that were not used. For instance, my 74 does not have any gauge in the lower left hole, so the backplane is factory cut and there's no way to install anything in that position using the factory backplane wiring. If you want to put in a tach I would suggest sourcing a new instrument cluster with the proper gauges in it already from the junkyard. At least this way all the bits and pieces are there and you can order parts as needed to refurbish the cluster yourself. If you can find the same year cluster with everything in it then it should drop right in with minimal wiring changes to make all the factory gauges work.

by the way, the factory tach in the mid 80s had an independent 3-wire harness going from the cluster to the ground/12v/distributor and it also had an inline resistor in the engine bay for the distributor wire. So, there is no wiring in the factory cluster plug for the tach, it's all independent. You can run your own wires because they are all just blade style plugs, but you'll have to find the resistor and put that in line, this is another reason to pull a factory cluster from the same model year becuase you can get the factory harness and resistor for the tach. Look up Hatzie's post that contains wiring diagrams, it should help

[Just call me Sean]

The lower left hole is where the clock goes. It has its own separate plug.