By Richard Ehrenberg. Copyright © 1989 Richard Ehrenberg and Harris Publications. Used by permission. First printed in Mopar Action
While resurrecting our Stealth Duster (er, make that "Rust Duster") for the One Lap of America, I made the not-toostartling discovery that the steering box was ancient history. No amount of fiddling with the sector shaft adjustment would produce a satisfactory result. Either it had a whole bunch of play at the wheel or, if the adjustment was snugged down enough to take out the play, the result was similar to turning a wheel connected to a fan blade in a bucket of molasses. Simply put, the steering wheel was acting strictly in an advisory capacity.
With 10,000-plus hard miles ahead of us, I needed a fix and I needed it fast. Rebuilding the box was briefly considered as an economy-related move but, based on previous experience, this was discounted. Typically, when the box is as shot as ours was, everything is shot, there's not much worth salvaging. Then, too, there was another fact to consider: We wanted better than stock, original steering if possible.
Luckily, I had the answer: a new, genuine Mopar steering box (actually a chuck, in Mother Mopar's official terminology). Not just any chuck, though: a police, firm-feel unit. Editor Steve Collison made a call to his good buddy Larry Shepard at Mopar Performance and, as if by magic, a carton containing one of part number 3643375 showed up at my door. Now all I had to do was put it in.
Truth be known, it was a snap for me for two reasons: I had done it at least a half dozen times before, and the engine was out of the car, providing unobstructed access. Not to worry, though, even if you've never seen a steering chuck, I'll walk you through it step-by-step and detail the necessary modifications, which are few.
The captions on the accompanying photos cover the process to the nth degree, but to assure continuity of thought, as well as to provide some insight as to why this swap works so well and ways to make it work even better, a full discussion of the setup is in order, so here goes.
All Chrysler RWD passenger-car power steering boxes since at least the early '60s are outwardly similar, being made of a housing of gray cast iron, with all parts contained therein. Except for the pump and hoses, there are no external parts-cylinders, linkages, etc.-as are present in some GM and FoMoCo setups. The sector shaft and sector gear ("output" shaft) are machined from a solid steel forging. A power-assist piston has teeth broached onto its outer diameter, and these teeth are in constant mesh with the sector gear. The wormshaft ("input" shaft) is geared to the inside of the power piston via a series of endless recirculating steel balls. Hydraulic circuitry is controlled by a valve body mounted on the top of the chuck, which directs the hydraulic pressure to the power piston as needed.
The firm-feel box, at first glance, appears identical to the standard unit. A careful inspection reveals that the reaction springs have been upgraded to increase road feel. The main difference, though, is in assembly: Careful, hand-select-fit is the norm, as opposed to slam-it-home for the more mundane units. Also helpful, of course, is the fact that it's a 100 percent new unit with 100,000 less miles on all the parts than a rebuilt or used chuck.
The result of all this upgrading is a box that comes close to duplicating the precise road feel of the better rack-and-pinion systems. In fact, to my mind, there is absolutely no technical reason why a recirculating-ball setup can't be every bit good as a rack setup. This is borne out by the fact that some of Europe's most highly regarded makers have steadfastly stayed with the ball-guide setup.
As I mentioned earlier, all Mopar boxes appear similar. The biggest year-to-year difference was a slight enlargement of sector-shaft spline size (where the gear arm bolts on) in the early 1970s. This, then, means that the police box will not be a true bolt-in on cars originally equipped with the smaller shaft. To complete the swap on these vehicles, the gear arm ("pitman" arm) will need to be swapped to a late '70s piece. Part numbers for these are shown in the parts table. Don't buy the new arm, though, until you try the original one on for size; it may just fit. Incidentally, the threaded portion of the sector shaft is the same in all cases, meaning that your original pitman arm nut and lockwasher can be recycled.
The return-hose fitting on the police unit is parallel to the wormshaft, while on most muscle-era Mopars the fitting juts up at a small angle. This is of absolutely no consequence, as the hose will easily attach to the straight fitting. If your car is a 100-point concours ride and you are afraid some show judge will notice, just swap your original nipple adapter (the aluminum casting) onto the new box. This is a two-minute bolt-on deal.
On every swap I've tried, which includes A-, B-, E- and even F-bodies, the unit has been a bolt-in, excepting the aforementioned variation in sector shaft size. I do know, however, that some vehicles use a larger wormshaft spline; I believe any variation here is limited to boxes used in vans and, possibly, C-bodies. If this turns out to be a problem in your case, all that would be necessary for a fix would be a change to a pot-coupling housing of the correct spline size.
A word now about a wild card: swapping from manual steering to police power. Aside from the obvious need to add a pump and hoses, there are two more "details." First, while the sector spline size was increased in the early 1970s on power-steering cars, it was unmolested on manual cars. This requires that the pitman arm be changed in every case. Second, the overall length of the power chuck is greater than that of the manual box, requiring a shorter steering shaft. The only rational way to cover this is to obtain a complete column from a junk vehicle of the same type as yours, but factory-equipped with power assist. Since the majority of Mopars were so equipped, this would not seem to be much of a problem; however, if for some reason the column should be unavailable, a competent machinist could no doubt shorten your original shaft the requisite amount, then remachine the "flats" required for potshoe contact and redrill a hole for the shoe-drive pin. This procedure, in my opinion, should be the course of last resort.
Anything you can do to the steering linkage to reduce deflection will of course increase steering precision. One way to do this is to increase the size of the tie rods. Most Mopars have historically used 9/16-inch tie rods. However, C-bodies, as well as a random sample of F-bodies, used massive 11/16-inch ends and tubes. These superstrong parts will, naturally, bolt into any F-car (Aspen, etc.), and they can also be used on damn near any other Mopar if the sleeve is shortened a bit, to match the length of the original sleeve. As near as I can tell, this shortening would be only about 1/a inch on A-bodies, while on B- and E bodies it's virtually a bolt-in fit.
Don't be conned into using the wrong lubricant. The only approved lube is Chrysler power steering fluid, part number 4318055. Anything you can do to keep the juice cool will, of course, increase the life span of both the fluid and all rubber parts in the system, such as hoses and seals. Therefore, pirating a small power steering cooler off of a junker is a good idea. Most cars equipped with 3.55 or steeper gears installed at the factory had one. The cooler simply mounts to the pump and gets "spliced" into the return hose.
With this swap complete, and a top condition suspension setup, the next item would be a good set of skins. Here's where we separate the players from the also-rans. A good set of H- or V -rated radials will make a world of difference, as will the widest, stockoffset wheels you can cram in your wheel openings. If you are trying to keep the resto, pie-tin hubcap look, try a set of part no. 3821550 wheels. These plain Jane 15x8-inch HD rims were originally used (optionally) on 1978 4WD Mopars, but they'll fit any Mopar with the usual 5-on 41/2-inch bolt circle, and they'll easily clear the wheel openings on E- and '68-and-up B-bodies. Forget about finding them new (they're discontinued), but there are a whole bunch of Trail Dusters and Ramchargers at the boneyards.
As for the rim protectors, 215/60VR,15s are nice on A-bodies (on 15x7 wheels), while E- and '68-and-up Bcars can usually accommodate 265/60VR-15s. I haven't yet found the limit, so I'm going to try some Pirelli P7s on my Road Runner in size 275/55VR,-15. Early Bs, especially 66-67 cars, usually can't go much larger than 225/70s due to fender (and rear quarter) interference. Incidentally, I've found that '63 to '66 A-cars actually have larger front wheel openings than the later versions, this being especially true of vertical (diametrical) clearance.
One quick note to the Pro Street set: Betcha didn't know that the larger tires actually belong on the front! Actually, as long as you don't ever go around corners, have fun with whatever floats your boat.
Have your front end aligned by someone you trust (I've recently begun to do my own, if you catch my drift). Be sure to go for the maximum positive caster, something like +2 degrees is usually attainable and really helps wheel return and straight-ahead tracking. If the tie rods are fresh, you shouldn't need much more than 1h6inch toe-in. Camber requires a bit of thought, however. The car will corner markedly better if it's decambered that is, if the top of the wheels are tilted in. I've found that something on the order of -1/z to -1 degree is about right. The only problem with this is that the tires wear rapidly, so I usually compromise at zero, with maybe -1/a or –1/4 degree on the right side to compensate for road camber-although, since most of us Moparites drive the "hammer" lane, this might not be such a good idea.
Gotta go now. My Road Runner's in the driveway and there's a new IROC-Z that needs humiliating in the slalom.
Other articles by Rick Ehrenberg
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