So I just bought another 70 SS454 which had the rear gears changed to 3:55s. While I like this gear a lot for local cruising (and tire spinning of course) it is not so good on the freeway. That said, I think I will leave it as is at least for now. Can anyone tell me if I can simply change the speedo gear in the transmission to correct the speedometer...it is currently reading about 90 MPH when doing 70 on the freeway.
Posted 11 November 2017 - 12:27 PM
1970 Monte Carlo SS454 Triple Black, Numbers Matching
2013 Cadillac XTS Platinum
2011 Ford Super Duty (F350) King Ranch
Posted 11 November 2017 - 10:34 PM
Here is another Calculator Tool to help you . If you know what your Drive & Driven gears in Transmission are, it will help in deciding what course of action to take. I had the same issue when I replaced the Rear End & gears to 331:1 ratio 12 Bolt Posi from a 273:1 ratio 10 Bolt if I remember right. I ended up putting a Gear Reduction devise between speedo cable at Tranny connected to devise and to Transmission. Damned if I can remember what the Technical name is. I was way off and brought actual speed within 1% of accuracy.
Pretty sure you will get a lot of help on this.
- stangeba likes this
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