4% speedo correction
Thread Starter
Pro
Joined: Mar 2007
Posts: 526
Likes: 1
From: San Angelo Texas
4% speedo correction
Ok guys, got one for you.
I have read up on the speedo correction and went to a website linked in the FAQ page. I had a couple of questions just to be clear.
1. Is the 3.45 gear standard in a 1990 M6 car? I have the adjustable suspension but my car is in storage so I can't look up the RPO codes.
2. Does anyone have pictures of the gear change? This is what the website kicked out:
New Driven Gear: GM # 25513047 - 40 tooth, black
New speedometer sensor: GM # 25007308
This is what the website said I need. The speedo gear is cheap so I am not worried. That speed sensor though is over $100. Looks like the drive gear is the same.
I have 18" C5 wagon wheels on all 4 corners with the stock C5 tire size of 275/40/18, which is 1" taller. I like the larger size, not to mention the slightly cheaper tires. I would like to keep the larger tires but need to correct that 4% error. Thanks all.
I have read up on the speedo correction and went to a website linked in the FAQ page. I had a couple of questions just to be clear.
1. Is the 3.45 gear standard in a 1990 M6 car? I have the adjustable suspension but my car is in storage so I can't look up the RPO codes.
2. Does anyone have pictures of the gear change? This is what the website kicked out:
New Driven Gear: GM # 25513047 - 40 tooth, black
New speedometer sensor: GM # 25007308
This is what the website said I need. The speedo gear is cheap so I am not worried. That speed sensor though is over $100. Looks like the drive gear is the same.
I have 18" C5 wagon wheels on all 4 corners with the stock C5 tire size of 275/40/18, which is 1" taller. I like the larger size, not to mention the slightly cheaper tires. I would like to keep the larger tires but need to correct that 4% error. Thanks all.
Pro
Joined: Jun 2007
Posts: 626
Likes: 2
From: Coquitlam British Columbia
Ok guys, got one for you.
I have read up on the speedo correction and went to a website linked in the FAQ page. I had a couple of questions just to be clear.
1. Is the 3.45 gear standard in a 1990 M6 car? I have the adjustable suspension but my car is in storage so I can't look up the RPO codes.
2. Does anyone have pictures of the gear change? This is what the website kicked out:
New Driven Gear: GM # 25513047 - 40 tooth, black
New speedometer sensor: GM # 25007308
This is what the website said I need. The speedo gear is cheap so I am not worried. That speed sensor though is over $100. Looks like the drive gear is the same.
I have 18" C5 wagon wheels on all 4 corners with the stock C5 tire size of 275/40/18, which is 1" taller. I like the larger size, not to mention the slightly cheaper tires. I would like to keep the larger tires but need to correct that 4% error. Thanks all.
I have read up on the speedo correction and went to a website linked in the FAQ page. I had a couple of questions just to be clear.
1. Is the 3.45 gear standard in a 1990 M6 car? I have the adjustable suspension but my car is in storage so I can't look up the RPO codes.
2. Does anyone have pictures of the gear change? This is what the website kicked out:
New Driven Gear: GM # 25513047 - 40 tooth, black
New speedometer sensor: GM # 25007308
This is what the website said I need. The speedo gear is cheap so I am not worried. That speed sensor though is over $100. Looks like the drive gear is the same.
I have 18" C5 wagon wheels on all 4 corners with the stock C5 tire size of 275/40/18, which is 1" taller. I like the larger size, not to mention the slightly cheaper tires. I would like to keep the larger tires but need to correct that 4% error. Thanks all.
I have a 1990 Vert A4; and went from 2.73 to 3.54. My VSS was a 34-39T and had to find a VSS # 25007308 which is a 40-45T for a driven gear. I also found out that this VSS on a A4 covers ratios from 3.07 to 3.73.
I used Masterframe Set to get my info on drive-driven and VSS and was dead on when I had the speedo checked with GPS.
Apparently right now you have a 42T green driven gear.
I dont have pics of setting gears but it looks like you may only have to change the driven gear to the 40T black one.
Hope this helps...
Bill
Team Owner
Joined: Sep 2003
Posts: 25,375
Likes: 2,734
I would do "NOTHING" until I mounted tire/wheel combination and confirmed the error with a GPS. You mention 1" taller but "accurate" speedometer calibration is done using a rolling radius rather than an advertised diameter.
Not all '90 MY cars were 3.45 some/many were 3.33 ratio.
The sensor in the trans now will do every driven gear with a tooth count of 40+ so if in fact you need a 40 there's no sensor to buy.
I don't know which calculator you've used but there are several that are "erroneous" but may be "ball park".
Not all '90 MY cars were 3.45 some/many were 3.33 ratio.
The sensor in the trans now will do every driven gear with a tooth count of 40+ so if in fact you need a 40 there's no sensor to buy.
I don't know which calculator you've used but there are several that are "erroneous" but may be "ball park".
