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.

Application Size Spline Dia. Spline
Ford Racks
Mustang II & Pinto – Manual 9/16″-26 0.563 26
Mustang II & Pinto – Power 3/4″-36 0.75 36
Ford Boxes
Manual & Power 3/4″-36 0.75 36
GM Manual Boxes
Vega 5/8″-36 0.625 36
Corvair 5/8″-36 0.625 36
Corvette (63-68) 3/4″-36 0.75 36
Corvette (69-82) 3/4″-30 0.75 30
Model 122 (65-85) 3/4″-30 0.75 30
  3/4″-36 0.75 36
Model 525 (86-Present) 3/4″-30 0.75 30
GM Power Boxes
Model 605 (78-84) 3/4″-30 0.75 30
Model 800 (77-Prior) 13/16″-36 0.813 36
Model 800 (77-Present) 3/4″-30 0.75 30
GM Racks
79-Present 5/8″-36 0.625 36
Variations 3/4″-30 0.75 30
Corvette (84-Present) 17mm DD 0.67 0.57
Fiero 17mm DD 0.67 0.57
Chrysler Box or Rack      
Omni Manual Rack 9/16″-26 0.563 26
Omni Power Rack 9/16″-36 0.563 36
Power Box 5/8″-36C   36
Manual Box 3/4″-36 0.75 36
Miscellaneous
Jaguar & MGB 3/4″-48 0.75 48
VW Rabbit – Diesel 3/4″-36 0.75 36

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.

Application Size Spline Dia. Spline
GM Column
Small Spline 3/4″-36 0.75 36
Large Spline 1″-48 1 48
Small DD 3/4″ DD 0.75 DD
Large DD 1″ DD 1 DD
Ford Column
Small Spline 3/4″-36 0.75 36
Small DD 3/4″ DD 0.75 DD
Large DD 1″ DD 1 DD
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