2-Minute Tech: How To Determine Steering Spline Size

Steering Shaft Sizes

To determine the spline size of a component (rack and pinion, steering column, and steering box), measure the outside diameter and count the number of splines.

If there is a flat spot on the shaft and some of the splines are missing, count halfway around where there are splines and double that number — you’ll need to know how many teeth are in a theoretical full circle.

Steering Shaft Splines

Common Steering Box and Rack Sizes

Use this steering box/steering rack size chart to select the proper rack and pinion or steering box spline size for your system.

If the chart does not list your application, just measure the diameter of the shaft and count the total number of individual splines. If there is a flat, count half of the splines and then double that number.

ApplicationSizeSpline Dia.Spline
Ford Racks
Mustang II & Pinto – Manual9/16″-260.56326
Mustang II & Pinto – Power3/4″-360.7536
Ford Boxes
Manual & Power3/4″-360.7536
GM Manual Boxes
Corvette (63-68)3/4″-360.7536
Corvette (69-82)3/4″-300.7530
Model 122 (65-85)3/4″-300.7530
Model 525 (86-Present)3/4″-300.7530
GM Power Boxes
Model 605 (78-84)3/4″-300.7530
Model 800 (77-Prior)13/16″-360.81336
Model 800 (77-Present)3/4″-300.7530
GM Racks
Corvette (84-Present)17mm DD0.670.57
Fiero17mm DD0.670.57
Chrysler Box or Rack   
Omni Manual Rack9/16″-260.56326
Omni Power Rack9/16″-360.56336
Power Box5/8″-36C 36
Manual Box3/4″-360.7536
Jaguar & MGB3/4″-480.7548
VW Rabbit – Diesel3/4″-360.7536

Common Steering Column Sizes

Use this steering column size chart to select the proper steering column shaft size for your system.

If the chart does not list your vehicle application, then measure your column’s output shaft. If it is a DD shaft (two rounds and two flats), then measure the rounds – it will either be a 1″ DD or 3/4″ DD. If there are splines, then measure the diameter of the shaft and count the individual splines.

ApplicationSizeSpline Dia.Spline
GM Column
Small Spline3/4″-360.7536
Large Spline1″-48148
Small DD3/4″ DD0.75DD
Large DD1″ DD1DD
Ford Column
Small Spline3/4″-360.7536
Small DD3/4″ DD0.75DD
Large DD1″ DD1DD