ZR-1    ZR-1    ZR-1    ZR-1    ZR-1    ZR-1    ZR-1

    Haibeck Automotive Technology



Speedometer Correction Gears


Speedometer correction gears are available for the 4.10 and 3.91 gear ratios. These gears fit the ZF S6-40 six speed manual transmission that was used in '89 - '96 Corvettes.


Axle Ratio    Tooth Count        Accuracy Relative to the Factory Speedometer Gears           Price for the Set

4.30                13/45                                        Within 1%                            The 45 tooth gear is no longer available.    

4.10                13/43                                        Within 1%                                                    $197.

3.91                13/42                             Speedometer reads 2% low.                                      $147.

3.73                15/45                                        Within 1%                            The 45 tooth gear is no longer available.

For the 3.73 axle ratio, the ZR-1 OE 3.45 gear ratio provides the 15 tooth (light grey) transmission shaft gear.

Note: The 45 tooth gear is no longer available from us and is very hard to find. GM PN 25513052. It was used only on the '84 Corvette with the 3.31 axle gear ratio.

To purchase, refer to the bottom of our Home Page by clicking Here.

The gears are easy to install. The tail extension housing does not need to be removed from the transmission.

1. Remove the exhaust system.

2. Remove the driveshaft.

3. Remove the speedometer sensor. Be ready for about 3 ounces of lubricant to emerge.

4. Push down the tab and remove the spring clip for the transmission shaft gear from the transmission output shaft.

5. Slide the original gear down the transmission shaft and out of the back of the transmission.

6. Oil the new gears and install them. Don't let the spring clip fly away!

7. Add 3 ounces of make up lubricant. The factory used GM PN 1052931. In 2007 PN 1052931 was replaced by PN 12345349. In 2012 GM discontinued 12345349. In 2017 GM PN 88900333 was available.We recommend Amsoil MTF 100% synthetic transmission lubricant. GM 12345349 and 88900333 are synthetic blends.