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lozrox58

Posted 2010-10-07 5:30 AM (#244591)
Subject: Rack and Pinion for a 59 Dodge

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Posts: 310
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Location: Newcastle Australia

I posted this a while ago on moparmarket. A few people have suggested I post it here. Bear in mind my application is right hand drive and the donor vehicles are Australian. But it gives an idea of what you go through to get rack and pinion steering.

The Dodge steering box and arms were replaced with a VS Commodore steering rack. To fit the rack a new cross member was made from 40*40 square hollow section shaped like the front cross member. The clearance from the sump is 15mm with the rack mounted beside the cross member.

The rack was modified with the ends of the rack shortened by 100mm. The rack body was left standard.

The distance between the inner tie rod ends was originally 585mm. The distance between the knuckles on the rack is 610mm. The 25mm difference results in bump steer of 4mm at top of travel. (measured with a bump steer gauge) I won’t know how much that affects things until I drive it.

Now the trick here is if you narrow the rack, the pinion tower will hit the sump.

The Commodore rack only travels 140mm from lock to lock. The original Dodge steering travel is 160mm. So the new rack reduces the full lock and increases the turning circle. To counter the change in turning circle I fitted XG Falcon ute stub axles.
The XG steering arms are 165mm from lower ball joint to tie rod end. The Dodge is 212mm.
The XG stub axles are 226mm high compared to 212mm for the Dodge.

I retained the commodore tie rod ends and dodge ball joints when fitting the falcon stubs.
The taper angle of the ball joints is different. The Falcon uses a taper of 1.2 inches per foot. The Dodge uses a taper of 1.5inches per foot. Both are standard sized tapers. The quote from the local engineer was $500 to $600 set up and $160 per hole. So I purchased a hand taper reamer off the net for $90 and did it myself. The amount of metal to be removed is 60 thousandths of an inch. A bloody long way with a hand reamer. To fit the stubs, the ball joint holes were bored out to fit the Dodge ball joint pins. Same with the tie rod ends. Holden uses a taper of 1.5 inches per foot (7.15 o) on the tie rod ends so a minor clean out of the hole is all that is needed to fit the Commodore tie rods.

The XG stubs also have another major advantage. They are already fitted with disc brakes.

For those who like numbers:-
Dodge distance between outer tie rod ends – 1210mm
Dodge distance between inner tie rod ends – 585mm
Dodge wheelbase – 122inches (3100mm)
Dodge track – 60.9inches (1547mm)
Dodge Ackerman angle inner – 27degrees (before)
Dodge Ackerman angle outer – 36degrees (before)
Dodge bump steer – 0mm (before)
Dodge king pin inclination angle – 7.2o

Commodore VS distance between tie rod ends – 1400mm (shortened to 1210mm)
Commodore VS distance between knuckles – 610mm

Falcon XG Ute wheelbase – 2957mm
Falcon XG Ute Track front – 1552mm
Falcon XG Ute Track rear – 1525mm
Falcon XG Ute king pin inclination angle – 9.4o

After the mod:
Dodge Ackerman angle inner – 27degrees (after)
Dodge Ackerman angle outer – 36degrees (after)
Dodge bump steer – 4mm (after)