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04-19-2018, 03:27 PM
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#1 |
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Registered User
Join Date: Apr 2012
Location: Chatt Tn
Posts: 982
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adjusting speedo on a 91 crewcab?
got a 91 454/4l80 crewcab I'm working on for a friend. speedo reads way too high, with the electronic speedo. pretty sure someone put a 3.42 or 3.23 gear in the rearend. how do you adjust the speed sensor setup from the factory? they had to have a way to do it.
__________________
88 military v30 crewcab shortbed 5.9 cummins, nv4500, 205 86 k30, 89 diesel burb, 76 gmc pathfinder 71 longbed 5.3 4l80 http://67-72chevytrucks.com/vboard/s...d.php?t=522535 |
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04-19-2018, 04:06 PM
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#2 |
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Registered User
Join Date: May 2012
Location: Colo Springs, CO
Posts: 870
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Re: adjusting speedo on a 91 crewcab?
Need to modify your DRAC unit that determines the pulses for you. Need to replace the straight wire with a block of toggle switches (Red Box below).
https://ck5.com/forums/threads/conve...p-pics.296187/ Input Ratio = [(63360)(Gear Ratio)(40)] / [(Tire Circumference)(128000)] Website: http://tbichips.com/?page_id=504
__________________
- Jeff 89' K5 Blazer, 2.5" lift, 35" tires  04' GMC Yukon XL, 3/4 ton, 8.1L Last edited by Ski-me; 04-19-2018 at 04:13 PM. |
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04-19-2018, 04:15 PM
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#3 |
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Registered User
Join Date: May 2012
Location: Colo Springs, CO
Posts: 870
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Re: adjusting speedo on a 91 crewcab?
DRAC box should be located just under the factory radio on the inner side of metal dash area.
__________________
- Jeff 89' K5 Blazer, 2.5" lift, 35" tires 04' GMC Yukon XL, 3/4 ton, 8.1L |
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04-19-2018, 04:22 PM
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#4 |
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Registered User
Join Date: Apr 2012
Location: Chatt Tn
Posts: 982
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Re: adjusting speedo on a 91 crewcab?
ok thanks
__________________
88 military v30 crewcab shortbed 5.9 cummins, nv4500, 205 86 k30, 89 diesel burb, 76 gmc pathfinder 71 longbed 5.3 4l80 http://67-72chevytrucks.com/vboard/s...d.php?t=522535 |
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04-19-2018, 08:18 PM
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#5 |
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Registered User
Join Date: May 2012
Location: horseheads,ny rust belt
Posts: 2,794
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Re: adjusting speedo on a 91 crewcab?
and some guy on ck5 modify's them if you cant . . . .
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77-k30lb BIG truck build . 87-k30lb budget beater build . 85-k30lb the plow machine build . 85-c10sb summer fun toy . ----------------------------- HOLLEY SNIPER efi = worst case of p.i.t.a i ever had . EDELBROCK pro flo 4 = best deal going so far . love my setup works great. |
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04-19-2018, 08:59 PM
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#6 | |
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Registered User
Join Date: May 2012
Location: Colo Springs, CO
Posts: 870
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Re: adjusting speedo on a 91 crewcab?
Quote:
Seriously though, OP, he does make them so plug and play for you. Infinite adjustments really. 👍
__________________
- Jeff 89' K5 Blazer, 2.5" lift, 35" tires 04' GMC Yukon XL, 3/4 ton, 8.1L |
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