changing dash to add tach

[kglowacky]

I have a 78 Silverado. If I wanted to change out the Base factory gauge cluster to a factory cluster with a tach is how of an issue is it to do this? Is it just adding a tach wire to my connection plug or are all the wires in the plug need attention? Did a 78 come with a tach option?

[kglowacky]

Just did a search on this topic on this forum. Plenty of info available. Looks like way too much work for what I would gain. Sorry everyone I should have searched 1st.

[Getter-Done]

I have wanted to do this swap also.

There is a lot to it depending on what setup you start with.

I like the big Fuel gauge to much to give it up for a Tach.

[ray_mcavoy]

Originally Posted by kglowacky

Just did a search on this topic on this forum. Plenty of info available. Looks like way too much work for what I would gain.

If your 78 already has the factory gauge cluster (not the warning light cluster) swapping in a tach cluster is not that much work. A 78+ tach cluster will be a direct plug-in swap and you'll just have to add the small stand-alone harness that has the power/ground/signal wires for the tach.

Things do get more complicated when doing things like swapping from warning light to gauge clusters (with or without tach). Or when swapping different year range clusters that have differences like ammeters vs. voltmeters or mechanical vs. electric oil gauges. These are the type of swaps where you have to get into things like re-pinning the cluster connector and making other changes that you likely read about in your searches.

[kglowacky]

I have a factory 78 gauge cluster( all gauges currently working) with big fuel gauge(on right) all gauges including the clock, what years will plug in look like original, and only have to do the adding wires for the tach? I think I've seen at least 2 different gauges faces

[ray_mcavoy]

Originally Posted by kglowacky

I have a factory 78 gauge cluster( all gauges currently working) with big fuel gauge(on right) all gauges including the clock, what years will plug in look like original, and only have to do the adding wires for the tach? I think I've seen at least 2 different gauges faces

Yes, the gauge faces changed in 1980. So to keep it looking original, you'll want to look for a 1978 or 1979 tach cluster.

Avoid the 1973 through 1977 tach clusters. Although they have similar looking gauge faces, these are the years with differences that prevent them from being a direct plug in swap into a 78+ truck.

You will loose your clock since the gas gauge ends up in that spot in the tach cluster.

GM never produced a cluster with both a tach & clock for these trucks. I think some folks have created them by adding a clock to a medium duty truck cluster (which has a small gas gauge at the bottom of the tach). But then you're getting back into 'more complicated' territory since it's no longer a plug-in swap.

Note that if you find a 78/79 tach cluster that has some defective gauges (anything other than the gas gauge or tach) you can use the working gauges out of your existing cluster as replacements.

[truckin 79]

It really is not that much work to modify your existing dash cluster to add a tach and gas gauge. I added a tach to my 79 I got lucky and scored a used tach that had a gas gauge at the bottom of tach as I wanted to keep clock. I do not have the clock powered though. The tach is easy enough to cut a hole and run wires to tach signal, power and ground. The gas gauge I just routed jumper wires from original spot to back of gauge. I did not solder the wire to spring clips; I just used some nuts and bolts to secure the wires to clips. It is pretty easy to do, I love having a tach to watch.
This thread is the one I followed
https://67-72chevytrucks.com/vboard/....php?p=7803354

[MJN]

Lots of good info here- you have make sure you get the correct gauge cluster for your truck
https://www.73-87.com/7387garage/int...achometers.htm

[SCOTI]

Originally Posted by truckin 79

It really is not that much work to modify your existing dash cluster to add a tach and gas gauge. I added a tach to my 79 I got lucky and scored a used tach that had a gas gauge at the bottom of tach as I wanted to keep clock. I do not have the clock powered though. The tach is easy enough to cut a hole and run wires to tach signal, power and ground. The gas gauge I just routed jumper wires from original spot to back of gauge. I did not solder the wire to spring clips; I just used some nuts and bolts to secure the wires to clips. It is pretty easy to do, I love having a tach to watch.
This thread is the one I followed
https://67-72chevytrucks.com/vboard/....php?p=7803354

I did a similar swap for my 89 CC dually. OE large fuel gauge removed for a repro tach w/the 'year friendly' font & purchased a small gas gauge to occupy the OE clock position (clock didn't work & I didn't care to replace it).