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.
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.
| Make | Type | Application | Size | Spline Diameter | Spline |
|---|---|---|---|---|---|
| GM | Power Box | Model 800 (77-Prior) | 13/16″-36 | 0.813 | 36 |
| GM | Rack | Corvette (84-Present) | 17mm DD | 0.67 | 0.57 |
| GM | Rack | Fiero | 17mm DD | 0.67 | 0.57 |
| GM | Manual Box | Corvette (69-82) | 3/4″-30 | 0.75 | 30 |
| GM | Manual Box | Model 122 (65-85) | 3/4″-30 | 0.75 | 30 |
| GM | Manual Box | Model 525 (86-Present) | 3/4″-30 | 0.75 | 30 |
| GM | Power Box | Model 605 (78-84) | 3/4″-30 | 0.75 | 30 |
| GM | Power Box | Model 800 (77-Present) | 3/4″-30 | 0.75 | 30 |
| GM | Rack | Variations | 3/4″-30 | 0.75 | 30 |
| Chrysler | Box | Manual Box | 3/4″-36 | 0.75 | 36 |
| Ford | Box | Manual & Power | 3/4″-36 | 0.75 | 36 |
| Ford | Power Rack | Mustang II & Pinto – Power | 3/4″-36 | 0.75 | 36 |
| GM | Manual Box | Corvette (63-68) | 3/4″-36 | 0.75 | 36 |
| GM | Manual Box | 3/4″-36 | 0.75 | 36 | |
| Miscellaneous | VW Rabbit – Diesel | 3/4″-36 | 0.75 | 36 | |
| Miscellaneous | Jaguar & MGB | 3/4″-48 | 0.75 | 48 | |
| GM | Manual Box | Vega | 5/8″-36 | 0.625 | 36 |
| GM | Manual Box | Corvair | 5/8″-36 | 0.625 | 36 |
| GM | Rack | 79-Present | 5/8″-36 | 0.625 | 36 |
| Chrysler | Box | Power Box | 5/8″-36C | 0.625 | 36 |
| Chrysler | Rack | Omni Manual Rack | 9/16″-26 | 0.563 | 26 |
| Ford | Manual Rack | Mustang II & Pinto – Manual | 9/16″-26 | 0.563 | 26 |
| Chrysler | Rack | Omni Power Rack | 9/16″-36 | 0.563 | 36 |
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.
| Make | Application | Size | Spline Diameter | Spline |
|---|---|---|---|---|
| Ford Column | Small Spline | 3/4″-36 | 0.75 | 36 |
| Ford Column | Small DD | 3/4″ DD | 0.75 | DD |
| Ford Column | Large DD | 1″ DD | 1 | DD |
| GM Column | Small Spline | 3/4″-36 | 0.75 | 36 |
| GM Column | Large Spline | 1″-48 | 1 | 48 |
| GM Column | Small DD | 3/4″ DD | 0.75 | DD |
| GM Column | Large DD | 1″ DD | 1 | DD |
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