speedo way off!
Thread Starter
Teching In
Joined: Feb 2020
Posts: 32
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From: Seacoast nh
speedo way off! I recently purchased a98 z28 a4 and the previous owner said gears had been put in. He said 3.42. I have the gu5 code, so should have had them anyways. At 40mph indicated, I'm actually doing 32 according to my gps. At highway speed, my speedo said almost 90, my rpms at about 2900, and im only doing about 72 according to gps. i also have a vibration from 60-70 indicated by my speedo, very well may not be related. Could only the gear ratio affect the discrepancy?
Thread Starter
Teching In
Joined: Feb 2020
Posts: 32
Likes: 1
From: Seacoast nh
Alright, thanks for the clarification. I knew that about the 3.23s too, just forgot. Whats the best way to recalibrate my speedo to the 4.10s? By the way, they are a little ridiculous for normal street driving.
Speedo has to be electronically (in the computer) altered with either a handheld device or taken to a place (or know someone) with a LS edit suite.
"By the way, they are a little ridiculous for normal street driving." I'm running 4.56 with the A4 in my 98Z and for me, they're wonderful.
Do you intend to leave them or change to a different ratio. Because the cars' computer still thinks there's 3.23s' in it, automatic shift points are way off. The speedometer gets its' signal from the reluctor ring mounted on the output shaft of the tranny in its' tailshaft housing. Once the computer is corrected for speedo correction, shift correction is also automatically done
"By the way, they are a little ridiculous for normal street driving." I'm running 4.56 with the A4 in my 98Z and for me, they're wonderful.
Do you intend to leave them or change to a different ratio. Because the cars' computer still thinks there's 3.23s' in it, automatic shift points are way off. The speedometer gets its' signal from the reluctor ring mounted on the output shaft of the tranny in its' tailshaft housing. Once the computer is corrected for speedo correction, shift correction is also automatically done
Thread Starter
Teching In
Joined: Feb 2020
Posts: 32
Likes: 1
From: Seacoast nh
I'll probably keep them, the instant grunt is great off the line, I just need to get some wider stickier tires. I was just concerned I'd run out of top end with the revs. Rpms are a little high for highway cruising, but I'm going to wait it out. There are other issues that need taken care of first. I'm not sure what maintenance has been done in its 117,000 mile life, so I have some sorting out to do. I have to figure out the vibes too, going to start with tires and all my bushings. For $3k, I really cant complain.
My tach is off be 150 so if I applied that to your 2900, 2750 would result. That makes more sense at 72mph. With the 4.56s' my rpm (using a ScanGaugeII) vs mph (GPS) is 2500 at 60 and 3000 at 72. I've taken 12 trips to Florida from the Cleveland Ohio area, 5 of which were with the 4.56s'. Freeway mpg with the 3.23s' was 24.5, 4.56s are 21.5. Not enough reason to change them.
Traction, get some bolt-in LCA relocation brackets and determine what the rear shocks are.
The next rear end I'm building is for with 4.10s so I can try those for a while.
Traction, get some bolt-in LCA relocation brackets and determine what the rear shocks are.
The next rear end I'm building is for with 4.10s so I can try those for a while.
