C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Speedo Question

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Old Mar 2, 2004 | 12:21 PM
  #1  
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Tonycino
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From: Littleton "Nitro must be the magic elixir in the Fountain of Youth"
Default Speedo Question

I have a customer that has a 93 LT1 auto with the 2.59 ratio. He wants to change to a 3.73 ratio, but also wants to true his speedo. My question is what did you guys do to true the speedo with that big of a gear change? Any help would be greatly appreciated.

Thanks in Advance,
Tony
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Old Mar 2, 2004 | 12:33 PM
  #2  
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Default Re: Speedo Question (Tonycino)

It will take a 1.44:1 reduction for a true speedo reading.
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Old Mar 2, 2004 | 01:46 PM
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Default Re: Speedo Question (Tonycino)

There are two ways to go.

First the more expenive, but I know these work:

http://www.ikerds.com/

Second way:

The gears that you need are easily available from gm. $20 or less for both. You need the Gray drive gear part #8642620 And lt blue 45 tooth driven gear # 25513052 This is a 3.73 with a 26 inch tall tire.

gmpartsdirect.com seems to have these. But again, I do not know if they really work accurately.
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Old Mar 2, 2004 | 02:50 PM
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From: Littleton "Nitro must be the magic elixir in the Fountain of Youth"
Default Re: Speedo Question (Flame Red)

There are two ways to go.

First the more expenive, but I know these work:

http://www.ikerds.com/

Second way:

The gears that you need are easily available from gm. $20 or less for both. You need the Gray drive gear part #8642620 And lt blue 45 tooth driven gear # 25513052 This is a 3.73 with a 26 inch tall tire.

gmpartsdirect.com seems to have these. But again, I do not know if they really work accurately.
Thanks for the links and the info I will let him know what to do. :cheers:
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Old Mar 2, 2004 | 03:39 PM
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Default Re: Speedo Question (Flame Red)

Oh, one other option. There is a little electronic gizzmo that I have seen that you can just connect in series to the VSS sensor. I think Ekler's carries it. You use DIP switches to recalibrate the readings using the stock speedo gears. Again, I don't know how accurate it is, but it sure beats swapping those speedo gears. I should know, I just spent 8 hours doing that job.
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