1956 Dodge and Plymouth

GM Steering Column Modification

Introduction

For some people, the factory Mopar steering wheels present a few issues ranging from the horn ring is often broken and extremely expensive to replace, the wheel plastic is usually cracked and requires expensive restoration, the factory wheels are large at 19″ diameter, the factory shaft splines do not allow interchanging other wheels, and no adapters are on the market to fit GM or Ford wheels. All of these variable got in my way with the 1956 Dodge coupe build, so I decided to look into installing a GM 3/4″ steering shaft with 11/16″ -36 splines, an upper and lower bearing that fits the ’56 housing and accepts the 3/4″ shaft, and modifying the ’56 turn signal switch to work with whatever wheel I installed. Because I was running rack and pinion steering, I no longer had the bottom of the column secured by the steering box and would need the shaft shorter for proper intermediate shaft u-joint angle. I quickly discovered that the quality bearing sleeves/bearings and steering shaft needed were as expensive as a new universal GM column assembly. I decided to purchase a fixed (non-tilt) 30″ GM universal column, gut the ’56 housing, and fit the GM column assembly into the ’56 housing (Figure 1). While I don’t have a Chrysler or DeSoto column to confirm, I surmise this process may work for all Mopar divisions at least in 1955 – 1956.

1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 1: 1956 Dodge and Universal GM Steering Columns
Column Modification

I began by removing the column from the steering box and car and removing the turn signal switch assembly. The first obstacle was the switch and bearing mounting plate that was spot-welded in four different places (Figure 2). I struck the plate downward with a cold chisel at each spot weld until the plate eventually tore loose (Figure 3). I will weld up and grind the indentations left on the outside of the housing from the torn spot welds. The next issue was the lower housing tube outside diameter of 1-3/4″ matched the GM column, so I cut off the ’56 housing where it flares larger and used a sanding disc to slowly trim the housing back until I could slide the GM column through (Figure 4). A similar issue, the GM turn signal housing was the same outside diameter as the ’56, so I slide the GM column into the ’56 housing until the both contacted and drew a line around the GM housing (Figures 5 – 6). I removed the GM wiring harness plug in order to remove the turn signal switch and harness. I used a cutoff wheel to cut along the line being careful not to cut into the turn signal towers (Figure 8). I eased the sharp edges with a sanding disc and slowly sanded the perimeter flat until the until slid snugly into the ’56 housing (Figure 7). For my setup, I chose to run an aftermarket American Retro 15″ 1957 Chevrolet wheel since its overall design mimics the ’56 Dodge with a full-circle horn right, ribbed rim, etc. I installed the wheel including the horn cam and spring. The steering wheel hub is smaller in diameter than the ’56 housing, so I will use an IDIDIT kit 2612100040 that includes an aluminum trim ring to install a 1955 – 1968 GM wheel onto a larger diameter universal steering column. This trim ring glues to the back of the steering wheel and is 3/16″ thick. With the ’56 column clamped in a vice, I dropped in the GM assembly until I measured 1/4″ between the ’56 housing and wheel to give me 1/16 clearance that can be adjusted by sanding the trim ring if necessary (Figure 8). I aligned the GM turn signal switch lever with the hole in the ’56 column. I marked the GM housing where it protruded from the ’56 housing at the bottom for a reference and marked the outside of the ’56 column to clearance for the turn signal lever and to drill a new hole for the hazard light knob (Figures 9 – 10). With the GM assembly removed, I drilled a 3/8″ hole for the hazard knob and used a carbide bit in the die grinder to clearance the turn signal lever hole (Figures 11 – 12). I reinstalled the GM turn signal switch and installed the GM assembly into the ’56 housing, feeding the wires through the hole. Using a 130-amp argon MIG welder, I tack welded the bottom of the GM column to the ’56 housing in two places (Figure 13). When I am confident the assembly functions as intended after test driving, I will continuous weld and smooth out this joint before painting the housing.

1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 2: 1956 Dodge Column Turn Signal Switch and Bearing Mounting Plate
1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 3: 1956 Dodge Column Turn Signal Switch and Bearing Mounting Plate Removed
1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 4: 1956 Dodge Column Cut Off for GM Column Clearance
1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 5: GM Housing Marked at 1956 Dodge Housing Contact
1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 6: GM Housing Cut to Fit Instead 1956 Housing
1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 7: GM Assembly Fit into 1956 Housing
1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 8: GM Assembly Positioned for a 1/4″ Gap between 1956 Housing and Wheel
1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 9: 1956 Housing Marked for Turn Signal Lever Clearance
1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 10: 1956 Housing Marked for Hazard Knob
1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 11: 1956 Housing Clearanced for Turn Signal Lever
1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 12: 1956 Housing Drilled for Hazard Knob
1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 13: Finished Modified 1956 Dodge GM Column before Paint
Turn Signal Lever Modification

The turn signal lever that came with the universal GM column looked out of place for the ’56 interior, so I installed the ’56 knob onto the GM lever. With the ’56 lever in the vice, I hit the side of a 1/4″ open-end wrench against the ’56 knob until it drove off. With the GM lever in the vice, I used a pair of vice grips to unscrew the knob that was secured with red loctite (Figure 14). At the bench grinder, I ground down the GM threads until the ’56 knob tried to fit snugly (Figure 15). I mixed up metal-reinforced epoxy that will withstand the temperatures of the chroming process, applied liberally to the lever, and pressed on the knob using a block of wood and hammer (Figure 16). After getting the assembly installed (photos in the next section), I decided to place a slight bend in the lever to align it parallel with the steering wheel arm (in progress).

1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 14: GM and 1956 Dodge Turn Signal Levers Disassembled
1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 15: GM Turn Signal Lever Machined for 1956 Dodge Knob
1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 16: Finished GM Turn Signal Lever with 1956 Dodge Knob
Finished Installation

I installed the column into the car to the factory location and installed the steering wheel (Figures 17 – 19). I am very happy with the assembly and the 15″ wheel and have two things to finish: I need to build a bottom mounting bracket to attach the 1-3/4″ column to the firewall since it can move around in the rubber firewall dust cover (Figure 20). I want to remove the steering wheel center resin emblem (held in place with metal tabs from the back), cut a piece of 1/8″ aluminum plate that I will either paint the color of the wheel or polish, and affix the 1956 Dodge Coronet steering wheel emblem (Figure 21).

1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 17: Modified Column and 1957 Chevrolet 15″ Steering Wheel Installed in 1956 Dodge
1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 18: Modified Column and 1957 Chevrolet 15″ Steering Wheel Installed in 1956 Dodge
1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 19: Modified Column Installed in 1956 Dodge
1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 20: Modified Column Base Requiring Firewall Mounting Bracket (in progress)
1955 1956 Dodge Plymouth Chrysler DeSoto Steering Column GM Chevy Conversion
Figure 21: 1956 Dodge Coronet Steering Wheel Emblem to be Used in Place of the 1957 Chevrolet Center