Silver Ghost Rear Axle Gear Ratio
Comparisons*

 Adapted from data compiled by David Morrison

 Four-Speed Transmission      

 

Rear Axle Ratio1 1st Gear 2nd Gear 3rd Gear 4th Gear Overdrive 3.71 (14/52) 3.40 2.22 1.49 1.00   3.71 (14/52 w/ OD2) 3.40 2.22 1.73 od 1.49 1.16 od 1.00 0.78 od             3.47 (15/52) 3.17 2.07 1.39 0.93 0.73 od 3.25 (16/52) 2.98 1.94 1.30 0.88 0.68 od 3.06 (17/52) 2.80 1.83 1.23 0.82 0.64 od 2.89 (18/52) 2.64 1.73 1.16 0.78 0.61 od 2.74 (19/52) 2.51 1.64 1.10 0.74 0.57 od

 

Three-Speed Transmission

Rear Axle Ratio1 1st Gear 2nd Gear 3rd Gear Overdrive 3.71 (14/52) 2.86 1.51 1.00   3.71 (14/52 w/ OD2) 2.86 1.51 1.18 od 1.00   0.78 od           3.47 (15/52) 2.67 1.41 0.93 0.73 od  3.25 (16/52) 2.50 1.32 0.88 0.68 od 3.06 (17/52) 2.36 1.24 0.82 0.64 od 2.89 (18/52) 2.22 1.17 0.78 0.61 od 2.74 (19/52) 2.11 1.11 0.74 0.57 od

 

*Tables assume a 14/52 gear ratio is the standard drive ratio; resulting in direct 1:1 drive in top gear.  All data is used to compare relative differences in gear ratios to a standard 14/52 rear axle. For example, the 4^th gear of the 14/52 rear end provides direct drive at 1.00, or one engine revolution per revolution of the drive shaft.  With the overdrive engaged, the engine rotates at .78 times the drive shaft RPMs.  Note that a 14/52 rear axle with a 22% overdrive provides a final drive of .78, or about the same gearing as an 18/52 without an overdrive.

 ¹Ring and pinion gears shown in parenthesis.

 ²A 3.71 rear axle “w/ OD” is listed to show the potential for ‘gear-splitting.’ In effect, you can engage the overdrive to create half steps between gears to more optimally match engine RPMs with the terrain.

Section 1 - Disconnecting Torque Tube
Section 2 - Removing the Front Section of the Torque Tube
Section 3 - The Mathematics of an Overdrive
Section 4 - Checking Universal Joint and Bearnings
Section 5 - Installing Overdrive in Drive Line
Section 6 - Overdrive Lubrication
Section 7 - Connecting Speedometer and Electric Controls
Section 8 - Hooking up the Electronic Control Box
Section 9 - Hooking up Speedometer and Calibrating Output
Section 10 - The Overdrive in Operation
Section 11 - Overdrive Service
Section 12 - Crusing in Overdrive
Endnotes - Endnote
Table 1 - Silver Ghost Rear Axle Gear Ratios Comparisons
Table 2 - Engine Revolutions per Tire Turn
Table 3 - Overdrive Speedometer Gears for the Silver Ghost