Tach Dash conversion
 

Hey guys, I'm wanting to know how difficult it would be to install a tach instrument cluster w/ the 100 mph speedo, in place of my 85 mph speedo, non tach cluster. I know that the tach won't be too hard to install, should be just like installing an aftermarket tach, but I want the 100 mph speedo, and I figured that would be harder. I've got actual guages vs. idiot lights w/ both clusters, so everything else should hook up okay, also, originally the truck had the stock 9.5x16.5 tires and I went to a 235/85/16, I believe the stock ones are aprox. 29" tall and mine are aprox. 32" tall, and I've got a 3 73 gears now, and am going to 4 10....so I'm wondering what all I'm gonna have to do in order to have an acurate speedometer. Thanks

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'81 3/4 ton Silverado Warmed up 355
TH400 w/shift kit
Corporate 14 bolt w/ 3.73s

Silverado6.6

To correct your speedo gears go to this website. You can type in your tire size and other information to find the gears you need.
http://www.tciauto.com/tech_info/speedo_gears.htm

As for installing the 100 MPH and tach the swap should be very simple. Your best option is to abtain the green ciruit board that the 100 MHP/tach were original removed. The green ciruit board will have the 2.5 inch gauge clusters wired correctly. In particular the fuel gauge since I'm assuming your truck came with the large fuel gauge on the righthand side. I've never done the swap but I have torn my truck apart enough to notice a ton of interchangeble parts from other years. Like digital guages? Check out my web page. I replaced the entire four small gauges with digital displays including a tach.

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Gerardo
1983 Custom Truck
TX Plates: "BAD BOW"
http://www.geocities.com/abetterchemist/