The Dodge Diplomat / Plymouth Gran Fury
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The 1980s saw the M-bodies (Dodge Diplomat and Plymouth Gran Fury) in extensive use as pursuit and detective cars. Though the standard 318 could not hold a candle to the 440, it proved to be extremely durable, capable of taking much abuse, and sufficient for most cops. The optional (in some years) 360 was more powerful and better suited to pursuit use, but relatively few squad cars of any make were pursuits. The 360 was dropped from ordinary Diplomats in 1981, but remained available for the police until (officially) 1984.
Most Diplomat 318 squads (keeping in mind that this includes municipal as well as state police vehicles; the latter are more likely to have pursuit options) seem to have been fitted with a standard two-barrel carburetors, as well as the usual electrical, suspension, and transmission upgrades, for use as detective cars and low-performance patrol duty.
The four-barrel carburetor added some power but had about the same torque; Danny Moore reported that they had roller cams and 360 heads. The 1975 318 four-barrel produced about 165 hp and 240 lb-ft of torque, while the 360 two-barrel produced 180 hp and 290 lb-ft.
On the smaller side, police could also order a slant six model, presumably for inner cities (where Motorola was more important than motorpower) and detective work, in some years. The slant six presumably worked well enough in cases where the police were unlikely to exceed 40-50 mph.
The Lean Burn system was common; some have recommended replacing it with a Mopar Performance electronic ignition system (with standard spark advance controls) due to its tendency to fail with age.
The E48 option was the 318 four-barrel; the E45, the 318 two-barrel; the general squad package, A38; and the 360, E58. In 1984, they switched to a new scheme, and the squad package became AHB, and the two and four barrel 318s became, respectively, the ELD and ELE. The AHB package would, until the end, provide firm-feel power steering; extra heavy duty suspension with front and rear sway bars, heavy duty front and rear springs, strut bushing, and shock absorbers; and wide-ratio TorqueFlite automatic.
Often forgotten was the slant six option; in 1981, the slant six powered M-bodies could muster just a 21 second 0-60 time, with a top speed of under 100 mph. Gas mileage was better than the V8 models, at around 18 mpg, versus the 318 four-barrel V8s pumping out around 165 hp and 240 lb-ft of torque but getting around 14 - 15.5 combined miles per gallon (in 1981). The V8 models, with 318s and four barrel carbs, were doing 0-60 in around 12-13 seconds, not bad for the time but not close to the muscle days. 100 mph came up in around 40 seconds, with quarter mile times of around 19-20 seconds. These were not muscle cars by any means, but they were tough and “fast enough.” (Times are from MSP tests.)
In 1984, the Michigan State Police tested the 318 two barrel and the four barrel, and found that the extra 35 hp and 5 lb-ft of torque in the four-barrel cars led to a hefty improvement in acceleration. The Gran Fury two-barrel managed 0-60 in 13.1 seconds, with a stunning 61 second 0-100 and 19.5 second quarter mile; gas mileage was, however, with a 2.94:1 ratio, 16.5 mpg. The Gran Fury four-barrel, weighing just 35 pounds more, ran 0-60 in 10.9, 0-100 in 34 seconds, and the quarter mile in 18.2. Gas mileage with the same axle ratio was 14.6 mpg, though. The two-barrel car had a 106 mph top speed; the four-barrel, 121 mph. Numbers varied each year depending on conditions, but aside from a 2.24:1 axle ratio on two-barrels in some years, they were moderately similar. (With the two barrel and 2.24 ratio, the 318 sucked down 14 miles per gallon, and did a 15-second 0-60 in 1989; but the top speed was up to 111 mph and quarter-mile time was 20 seconds.)
The heavy-duty A-727 automatic transmission appears to have been dropped in 1983, leaving the capable, for most uses, A-904 or A-999 in its place. Danny Moore wrote that the A-998 had four or five clutches while the A-904 had three; by 1975, the A-998 was used with the 360 two barrel, and by 1983 the A-727 was changed to the A-904 in squads. (Torqueflite details.)
The "economy" rear gear ratio of the later squads (2.24:1) reduced acceleration and top-end speeds (the 2.94:1 ratio was also available); the result was a V8 powered squad car (Gran Fury, 2-barrel 318) that had the same acceleration as the 2.2 liter Plymouth Reliant. Unfortunately, the Diplomat never saw the Magnum head, cam, manifold, and fuel injection treatment that would raise power from to 230 hp. By 1988, the standard 318’s gas mileage was rated by the EPA at a lowly 15 city, 19 highway.
Duane Hughes pointed out: “The 360 police engine was identical in output to a standard 360, but toughened for continuous high speed use with a double roller timing chain, forged crank, and windage tray. These engines were also standard in the Volare Super Coupe.” The 360 two-barrel was capable of 155 hp in 1977 — compared with the 150 hp of the 318 two-barrel in 1976 Valiants.
Former police officer and fleet manager Curtis Redgap wrote,
The Diplomat (Gran Fury) really did well against the Ford Crown Victoria, in part because it was a better POLICE package, as opposed to a civilian rig. Chrysler Fleet knew then how to meet and beat bidding. Straight up in 1984 (the last year I was Fleet Manager), the Gran Fury outpointed the Impala and the CVPI in Michigan, and LA. The only shortcoming was those front shock suspension towers with the weakened front end braces. If Chrysler had redesigned the front suspension to the older style parallel torsion bars, the cars would have been far more acceptable.
For the time, the 318 equated itself well. While it may not have been as powerful as the "old" school guys (like me) liked, it was fast enough, and rugged enough to fulfill 50-60,000 miles of police constant abuse without whimpering. Once the front suspension weakness was identified, and fixed, (the problem did NOT cross over to the civilian models) the Diplomat and Fury really were great patrol vehicles.
In 1989, Chevrolet launched a new fuel-injected Caprice, and it was far more challenging than past models had been. The Caprice bested the Diplomat and Gran Fury in every category but braking and interior egonomics. The writing had been on the wall for years; and in 1989, the last Dodge Diplomat and Plymouth Gran Fury ran their way down the Kenosha line.
The last year for the Diplomat and Gran Fury was 1989.
Another source wrote: (A) county in Florida took several 1988 and 1989 Diplomats and worked them over to become drug interdiction cars. The 318 was replaced by the new crate motor from Direct Connection. Rumored horsepower was a manageable 350 net (!) with about 425 foot pounds of torque. Top speed was in the neighborhood of 145 with these cars. Naturally the chassis and brakes were changed to protect the innocent. The units are still being used sparingly for special cases.
Curtis Redgap wrote that the last Mopar cruisers used by the FHP was the 1987 Diplomat, with the four-barrel 318. It is claimed that the factory dropped several hundred 360 engines into the FHP Dodges. These less than aerodynamic styled jobs had a 130 mile an hour top speed and could sprint to 60 from rest in 8 seconds.
Dennis O'Connor wrote: These cars were also used by New York county Sheriffs departments and I personally saw them in the eastern most counties near Connecticut (where I live). At the time, late 1980s and early 1990s, I was part of a drum and bugle corps that marched all over Putnam County NY and adjoining counties. The cruisers were very nice looking (white with green and tan markings) and VERY fast with great handling. I saw several on the 2 lane state roads that were their stomping ground (versus NY State Police on the Interstates) in full pursuit/response mode and they were unreal. Those were not 318s for sure and they cornered far better than my much improved Camaro from that time. Whenever I got to talk to a deputy about the cars they said they loved them and only smiled when asked details like engine size. Don't know if I can ever find out more but will keep you in mind if I do.
"WWBroach" wrote: I am not positive about this but it's a theory. Ford released the 4.6 in the Mustang in 1996, but our 1992 Crown Victorias had the 4.6 engines...our motor pool said Ford was using the police cars to test the durability of the new engine. It may be that the late 1980s mopars were 318s, but with Magnum heads doing the same testing. I thought about this because I have a friend with a Duster that he has put a basically stock 5.2 Magnum converted to a 4bbl in it and you would not believe the power this thing has for a production small block.
Danny Moore added: Remember the new gas tank shield they have started putting on the new Crown Vic police packages? Well, my Diplomat already has the shield between the rear axle and the gas tank, and it is 15 years old!
Problems
I was never convinced that a used squad made for a decent daily driver. The only way that I ever saw any success in that respect was a complete, detailed overhaul. Essentially, when the wrench work was done, the car was mechanically brand new.
Another terror to beware of in the "M" bodied Diplomat and Gran Fury was the suspension towers. All of a sudden you couldn't keep the babies in line, and got some real squirrely handling. It took Chrysler a while to figure this one out. However the shock towers of the front suspension sagged inward! LA and LA Sheriff banned the transverse torsion bar suspension from participation in the bidding process. This problem started showing up as early as 1980!
To make matters worse, the K-member of the frame where the suspension was mounted, cracked, allowing further degradation of the sagging due to low quality tensile strength steel. This was particularly evident in the 1984, 85, 86 and 87 "M" bodied cars.
Once the suspension exhibited the nasty habit of going out of alignment within hours of having been reset, the only cure was replacement of the K-member and the shock towers. A rather expensive fix.
As a sort of back handed tribute to Chrysler engineering, this "out of alignment" problem was related ONLY to severe service, i.e.: Police cars and or taxis. It was also directly proportional on the type of driving it had received. The NYC police, operating on the bombed out streets of the Bronx and Manhattan, had suspension problems within weeks. A Nevada Highway Patrol might never had exhibited any problem at all. No civilian vehicles were ever reported with this sort of problem. Chrysler did solve the situation by 1986, however, they won't discuss the cure, unless you happen to be a Police Agency with a suspension problem! They did NOT make the fix at the manufacturing end until 1988. The tower mounts had to be replaced, and the K-frame as well.
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