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post #1 of (permalink) Old 05-08-2002, 09:51 PM
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I have no speedo...no...not the swimsuit, but the indicator. I was off about 10 mph when it did work and want to change the gear reducer anyhow, even if that doesn't fix it (might be a gear in the t-case). My ordeal now is that the local chevy dealer has no idea how to find out which unit to use. I was showing to go about 50 when running 60mph or so. I am running a 350 th trans, 3.73 gears and 31/10.5/15 tires. Isn't there a method of calculating this? The gear reducer on my truck is 1: .866 which is discontinued anyway. I need to make the speedo see me going about 10mph faster at highway speed. Which number needs to change? The (1) or the (.866) is my question I guess. This is on my 69 gmc with 75 axles. Hope someone has an idea, I may get a ticket guessing my speed all the time!
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post #2 of (permalink) Old 05-08-2002, 10:22 PM
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Re: speedo

Check the cable(s). If you've got cruise control it's mechanical and you'll have a box under the hood somewhere.

As far as changing the pickup gear in the transmission or transfer case, I don't know.

I've never had a vehicle that had the speedometer correct. My Sonoma was going 70 when the speedo showed 59. It's not a big deal as long as you remember that it's off.
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post #3 of (permalink) Old 05-08-2002, 10:58 PM
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Re: speedo

I really need to change out the reducer, and want to know how to correct the thing. I definitely don't have cruise on a 69 gmc! Cable is good, and reducer has to change as it is leaking and won't seal properly, may fall apart any moment. Just want to try and get the right one while ordering one. 55 bucks and want to get it right the first time!
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post #4 of (permalink) Old 05-10-2002, 03:37 PM
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Re: speedo

Here is a site with a chart on it for GM speedo gears
Hope that helps
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