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Big Port Jimmy 6 · 12-10-2013, 12:15 AM

The speedo on my crew cab has always been 4-5 MPH slow. (01 5.3 /4L60E). The tune was supposed to be set up for the tire size but? I am using a 91 cluster. I just went bigger on the rear tires and now the speedo is 10ish MPH slow. I wonder if adding a modified Drac would correct this.

As I understand it I would install the Drac in between the VSS and the PCM
And would have a separate out put for the speedo. I have seen the article about modding a drac for my input. The question is if the later 4l60 outputs 40 pulse per rev/4000 per mile. . Jay

12-10-2013, 12:15 AM	#1
Big Port Jimmy 6 Addicted to Rust Join Date: Dec 2009 Location: Abbeville SC Posts: 1,030	Any thoughts on adding a DRAC The speedo on my crew cab has always been 4-5 MPH slow. (01 5.3 /4L60E). The tune was supposed to be set up for the tire size but? I am using a 91 cluster. I just went bigger on the rear tires and now the speedo is 10ish MPH slow. I wonder if adding a modified Drac would correct this. As I understand it I would install the Drac in between the VSS and the PCM And would have a separate out put for the speedo. I have seen the article about modding a drac for my input. The question is if the later 4l60 outputs 40 pulse per rev/4000 per mile. . Jay __________________ Current trucks: (48 GMC100 320 inliner) Gone (48 Suburban in pieces) Sold 87 GMC CCSB 5.3 4l60E Daily Driver ECTA National record holder XO/PP We never really grow up, we just learn how to act in public.