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2002 Chevy Astro LS
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I just rebuilt my rear differential and changed the ring & pinion gears from the factory 3.42 gear ratio to 3.73. So far everything is working good, very quiet and smooth. My old pinion bearings had gone bad after 263,000 miles and were making noise. The only problem, and I knew this would happen, is that my speedometer is reading about 7% higher than my actual speed. I was thinking about getting a Yellow Box Speed Recalibrater (Official home page of the Yellow Box Speedo Recalibrator). Does anyone know much about them or a better way to get my spedo accurate
 

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Common Sense + Critical Thinking
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13,079 Posts
I wouldn't waste my money on the speedo re-calibrator, waste of $ as you can just change it in your PCM.

I have used PCM Hammer/TunerPro and they do work as long as your PCM and OS is supported, which should be the case with your 02, should have the 0411 PCM in it.
Here are the supported devices: SupportedDevices · LegacyNsfw/PcmHacks Wiki
So as long as there is a XDF file available for your OS, then no problem.

I have the wifi version of the VXDiag device Amazon.com they also have a slightly cheaper USB only version, both can be used with the Tech2Win emulator(Tech2 is the factory scan tool) and also with PCM hammer. The OBDlink LX is cheaper and quite fast Amazon.com as well as working with your phone/tablet for easy code reading.

While you can't use the Tech2 or Tech2win to change your gear ratio, it does give you automated ABS bleed and cam/crank relearn.


If that doesn't appeal to you, send me a PM and I will hook you up with that change. But shipping isn't super cheap and would get you part way to buying your own device. Unless someone else is in his area and wants to lend a hand.
 

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My 02 has 3.42. 200K on it so far. I pulled a 3.73 from another van a few years back to swap, also got another 0411 PCM. That PCM was from an 01. I had a local guy mirror my existing PCM to the spare 01 (eliminates EGR among other things) and set gear ratio to 3.73. I think he charged me $30 or $40.
Still haven't swapped as we don't use this van for long loaded road trips any more. It still goes but gets dragged behind an RV. When/if the 3.42 ever has issues I'll do it.
 
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