PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

GPS speedo with 4L60e

Old Jun 23, 2015 | 12:15 PM
  #1  
iceburgh's Avatar
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From: Mechanicsburg Pa
Default GPS speedo with 4L60e

I finally have a tuner that is going to flash a PCM and send it to me. That should get me going down the road.
However he said he believes that the fact I am using a GPS speedo that is the culprit to my tranny issues not shifting or shifting correctly.
If that is the case is there a work around to this.
I am not looking to spend another $600 on a speedo and tear the dash apart to put it in.
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Old Jun 23, 2015 | 01:34 PM
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LSX Power Tuning's Avatar
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I tune swap cars all the time with GPS speedo's. It has zero affect on the transmission shifting. When I plug into the car I can still see the VSS from the transmission and as long as that matches your actual MPH it will shift fine. You still have to set the tire size, gear ratio, and shift points correctly. The pcm has no idea if you have a speedometer or not and doesnt care.
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Old Jun 24, 2015 | 08:15 AM
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iceburgh's Avatar
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Originally Posted by LSX Power Tuning
I tune swap cars all the time with GPS speedo's. It has zero affect on the transmission shifting. When I plug into the car I can still see the VSS from the transmission and as long as that matches your actual MPH it will shift fine. You still have to set the tire size, gear ratio, and shift points correctly. The pcm has no idea if you have a speedometer or not and doesnt care.
Thanks for the info.... not sure the guy wants to do the tune now.
I see you guys offer mail order. I will be in contact.
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Old Jun 25, 2015 | 06:59 AM
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VSS just needs to go to computer. Ignore the output from the computer for a speedometer. But I'm fairly certain you have to retain the VSS (VSS is not the same as speed output wire in ECM) otherwise your trans won't know when to shift. You don't have to use a speedo and your car will operate fine with VSS only. So GPS speedo is another tool for calculating the speed and is a separate entity. Sorry for being repetitive but just wanted to try and be clear.
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