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1977 Tachometer into a 1990 Cluster

Discussion in 'The Garage' started by hawkeye649, Nov 4, 2005.

  1. hawkeye649

    hawkeye649 1/2 ton status

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    Well I put the 77's gas where the battery idiot light used to be. I put the tach where the big gas gauge used to be. I hooked it all up and everything worked for a few days. Then the tach started randomly jumping around and finally just stopped around 4K. I checked all the wiring and it seems to be correct - ground, 12V, and Hz at the coil wire. These gauges were a little nasty out of the 77 so I re-painted them, the gauge may have been on it's way out no way to know.... I can't get the gauge to do a thing so either I fried it or it just died? Thanks for any input....
     
  2. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Sounds like it quit. When mine quit, it started swinging around wildly like that, then suddenly just quit too, cept mine stopped at 5 k, not 4, lol

    I replaced it with a new one, and no problems since.
     
  3. hawkeye649

    hawkeye649 1/2 ton status

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    Where were you able to pick yours up? When I opened up my LMC they didn't have any in there - I haven't really looked but help is help. Even the local 'yards don't have much in the way of K5's any more "We only do '95 and newer" is the common response when I call 'em....

    GMC Gremlin
     
  4. hawkeye649

    hawkeye649 1/2 ton status

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  5. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    Try this - TachMan.com I believe they can fix a dead tach.

    Did you use a factory wiring harness? There is a resistor in the OE harness.


    What did you have to do to the plastic "box" the gauges are in? Did you have to cut a hole in it for the tach? Pics?
     
  6. hawkeye649

    hawkeye649 1/2 ton status

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    A resistor in the wire, eh? No I used my own wire, I have the '77 and most of the harness is hanging out of it, but I didn't see a plug that fit into the tach so I just said "whatever" and attached them with simple female quick-disconnects. I'll have to see if tach man is reasonable, cuz I would really like to keep the factory gauges I like the way they look and I don't need a friggen 10,000RPM gauge, when it was working I had my truck in 3rd (th700) at 70, floored it forcing a shift change, and I think it got to 4K??? LOL Plus I'm sure his screening would look better than my painting.

    Nothing really hard, for the tach. Just cut out a square hole for the prongs to stick out, the factory flexy circuit board actually has a missing square exactly where it should be. The tach also has a support bracket, and the mounts/holes where this attached in the '77 are still in the '90. A little trimming here and there for clearance and it all bolted together as though stock.
    The gas gauge was a little harder, there are a bunch of walls over there to seperate 2 idiot lights where a clock normally would go. I just nipped those all out, cleaned it up, and then grafted in a little bit of the '77's cluster box so I had a post to attach it too. Probably could have just attached the post to make it simpler, but I thought this looked better and it provided the squares where those nifty clips attach, though I didn't end up using them and thought I would.

    Don't make fun of my crappy paint job, block letters with a brush are hard.
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     
  7. hawkeye649

    hawkeye649 1/2 ton status

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    The tach man said he could fix my tach, but not make it work in my '90 - and he'd never been asked to silk-screen a truck tach so it would be like $200 to set up just the screening. Looks like I may be hukkled.
     
  8. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    Thanks for all the pics! I've got a tach cluster coming next week so I'll be putting it in my crew cab soon. I've always thought the OE stuff was uber secksy!
     
  9. keifer

    keifer Registered Member

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    A friend of mine in Ohio had about 2 extra tach clusters last year, if your interested i can find out if he still has them. He actually offered me one, but i didnt need it as i already have one.
     
  10. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    Yeah, see if they are still available. I'm specifically looking for the 85mph speedo style (number font is different than the earlier style).

    Edit: of course, if Hawkeye needs one to replace his dead one he's first. :wink1:
     
  11. hawkeye649

    hawkeye649 1/2 ton status

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    Yes please. I really only need the tach but we'll see what's what.

    GMC Gremlin
     
  12. hawkeye649

    hawkeye649 1/2 ton status

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    Ya the font difference in the tach kinda bugged me, but I could have left it. But the surface rust on the gauge was unforgivable so I painted it over again.

    GMC Gremlin
     
  13. keifer

    keifer Registered Member

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    Just got off the phone with him, he said he has 3 or 4, one for sure is the older style. He would have to check all this to verify that they are good. He gave me a price also, I can give more details tommorrow, as I am leaving from work now.
    c/ya
     
  14. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    Yeah, I've got 3 of the older 100mph tach clusters but I held out for my crew cab.
     
  15. hawkeye649

    hawkeye649 1/2 ton status

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    Hello, what say you any news?

    GMC Graemlin
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    The only special piece I'm aware of that was used with tachs (and only in certain applications) was a capacitor(?) to keep interference from screwing with the tach.

    I don't believe not having it would do anything other than make your tach read funny in extreme circumstances. I know I don't have any of that on mine and it reads fine.
     
  17. hawkeye649

    hawkeye649 1/2 ton status

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    So I take it you have an old tach in a new HEI equipped engine - and it has worked for a while now??

    GMC Graemlin
     
  18. sandawgk5

    sandawgk5 3/4 ton status

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    I have one in my truck and I have an 1987 with TBI. Mine was reading wrong and I was turned on to a guy on http://www.67-72chevytrucks.com/ . His screen name is Necromancer and he can repair and recalibrate factory tachs. He converted mine into a 7K tach and printed a new face much like the white conversion kits but it matches the factory 87 numbers. If you need pictures I can try and get some. It is pretty dark out but I can try.

    Anyway look him up he was a lot more reasonable than tach man. Shoot me a PM if you want to know more.

    Ira
     
  19. dyeager535

    dyeager535 1 ton status Premium Member

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    Old tach, new tach, same setup. Three wires: +, -, coil lead.

    I found an '81 tach (last year they were available *apparently* as I can't find any documentation saying they existed after that) but prior to that I was using a tach out of a late 70's Camaro. I had older truck tachs, but never bothered to swap one in because of the font difference.
     

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