Dash pictures of ‘77 K5 Blazet w/tach

I am looking for pictures of ‘’77 Blazer dash with tachometer. I want to search for the correct gauge so it matches the speedometer. It could also be the same part number as from a pickup C10 or C20?

Yes, same year pickups used the same gauges.

I think 78 was when the font changed and speedos also went from 100 mph to 85. Early 70’s squares used an amp gauge instead of the later volt gauge so the related wiring / printed circuits are different.

You’ll need the tach, small fuel gauge, cluster housing and printed circuit to do the conversion.

nvrenuf said:

I think 78 was when the font changed and speedos also went from 100 mph to 85. Early 70’s squares used an amp gauge instead of the later volt gauge so the related wiring / printed circuits are different.

You’ll need the tach, small fuel gauge, cluster housing and printed circuit to do the conversion.

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They didn't go to 85mph until very late in '79, maybe. Either that or, the very early '80 models got the 85mph speedo, but not the new for '80 font.

'77 got a voltage gauge, but still had a mechanical oil pressure gauge. In '78, the switch was made to an electrical oil pressure gauge, along with a different cluster housing and printed circuit.

Thank you… there are a few NOS guages for sale out there and it is hard to know when they changed. Does anyone have a part number I could reference?

Don't bother with the originals. Just get Dakota digital and never look back. I put these in a 1980 c10. The accuracy, ease of installation, and light systems is so much better..

Paul Ristow said:

Don't bother with the originals. Just get Dakota digital and never look back. I put these in a 1980 c10. The accuracy, ease of installation, and light systems is so much better..

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Everyone doesn’t like digital. I prefer the look of a factory tach set up, to me digital just doesn’t match the look of the truck.

The actual digital gauges like intellitronix, agreed, not a fan.

DD RTX gauges on the other hand…


I do like and enjoy the factory gauges too.

nvrenuf said:

Everyone doesn’t like digital. I prefer the look of a factory tach set up, to me digital just doesn’t match the look of the truck.

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I have the HDX and love them.

It’s hard work gathering the parts and building a factory tach cluster, but it’s totally worth it. One tip, an easy way to tell the 80&up factory tachs from the repro tachs is that factory tachs have the telltale/redline. It’s yellow/red in the earlier 80&up tachs and white in the later tachs. All the 80&up repro tachs I ever saw had no redline indicator. Looks like 73-77 factory tachs had no telltale and 70-80 had it.

Here’s a pic of the cluster I put together earlier this year for my 1987 V10 Silverado, 1st year for the 5.7TBI in trucks. Looking online there’s a lot of bad info out there, a site stating that you can’t run a factory tach on a 1987&up truck with TBI. Well, I did it. I found a NOS 88-89 Speedo with trip odo, (My speedo had just rolled over so perfect time to add that new speedo with trip odo), got a lens with the hole for the trip odo reset shaft out of a 1991 Suburban, the factory tach and cluster back out of a 85 3/4 ton manual transmission truck in the junkyard, (had to use a dremel on that ‘85 tach cluster back to make room for the back of the ‘87-‘89 speedo with VSS plug), a correct for 1987&up small fuel gauge with the circle indicators for full/half/empty, new circuit board for the tach from Cajun Tach Shop with a potentiometer on the board so I could dial the tach in, new printed circuit and wiring through the firewall to the fuse box and cluster from LMC, tach signal filter from a 1984 Z28 in the junkyard and wiring from ignition module to coil that also had both ends of the tach connector from a 87-92 TBI/TPI Camaro/Firebird I found on eBay. BTW, I ran the tach off the white tach signal wire that was already there off the coil at first but since I found that both the connectors on my coil had broken clips I made sure to buy replacements for them off a TBI car with a factory tach so I’d have both ends of the factory tach wire connector too. I used the accessory gauges and transmission gear indicator that came with my truck and the best of the clips/sockets/lenses/etc from my old cluster and the parts cluster. Painted the faded needles with Testors fluorescent orange paint.

IMHO this is what the BC3 “Deluxe Instrument Panel” SHOULD have been.

GM also had issues with the electric board on the back of their tachs in the 70’s. There are multiple sites with a replacement board for Corvette tachs, but nothing for the squarebody. I’ve also seen articles explaining how to fix the factory board by repairing a circuit trace and replacing one small component, but never researched them enough to know if it works well.

75gmck25 said:

GM also had issues with the electric board on the back of their tachs in the 70’s. There are multiple sites with a replacement board for Corvette tachs, but nothing for the squarebody. I’ve also seen articles explaining how to fix the factory board by repairing a circuit trace and replacing one small component, but never researched them enough to know if it works well.

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That is great to see there is a replacement board for the original truck tachs!
I read the old articles about how make your own repair, but my tach still works (so far), so no need for a fix yet.

From 77 blazer