Several General Questions

[TomO]

Hello -- I had several general questions that I thought someone would be able to answer. I've done some searching, but wasn't able to find definitive answers:

1) I have an '89 Grand Marquis with the towing package, which appears to have a 3.55 (k axle code) limited slip, front and rear sway bars, auxiliary transmission fluid cooler, and factory dual exhaust.

My question here is -- what are the main differences, if any (other than the obvious trim differences), between my car and a Crown Vic Police Cruiser? I don't know a lot about the Police Cruisers, but the only difference I come up with is the tire size difference (mine has 215/70R15's and the Police has 225's).

2) So, my next question is, would there be any considerations to think about when putting 225's on my car? I would like to get a bit of a beefier tire look without going too much bigger. I figure the 225/70R15's would be about right. The 225's don't seem to be so much bigger that I'd notice a difference in braking or acceleration, or anything else, but I would like to hear from anyone who knows for sure or who has had experience in doing this. Would it be safe to put the 225's on the stock aluminum turbine wheels? I believe these are only 6" wide, whereas the police wheels were 6.5.

3) Next question is: I know someone who has a '97 Crown Vic with the HPP. The axle code on the factory tag is a "5" which apparently means 3.27 ratio, open differential. I was under the impression that the HPP included limited slip differential. Apparently, I'm wrong. Anyone have any info on this?

Thank you for your time -- I appreciate any input and info.

[marquisman]

the old man has 225/70 R15s on his 88 wagon and say they are much better than the 215 series(i wouldent even bother with 205s)

[p71towny]

HPP should be posi yes.

[Southern_Pride]

225's will fit on those wheels. Ive run much wider than that on them.

[86bbub]

arent stock steelies 15x6.5? i think i remember having a couple tire places tell me the max they would put on the factory rims was 255 70 R15... i had 235 75 R15 on stock steelies at one point, plenty of roll lol NO handling

[crown vic muscle]

i have 235's on 14 steelies with no problem, i think its 6", could be 6.5" though.

[1987cp]

235/75 is more for a winter light-truck tire ... it's 29 inches tall!

You *can* run as wide as a 255/60 on a 6.5" rim, considering only tires under 27.5" tall, but while it looks neat, it can produce wallowey handling and funky wear patterns. A 225/70 is only marginally taller than the original 205/75 or 215/70 and probably won't even throw your speedometer off.

Having recently acquired an '87 ex-police car, my best answer for differences between a base Vic and the more upscale Grand Marquis is lack of luxury equipment. My particular car has tilt steering, power windows, and map lights, which were evidently standard by '87, but features no cruise control, manual remote mirrors, manual bucket seats, and no weight-adding and rust-encouraging vinyl top. Not uncommon to find split benches in cruisers, however - I'm told lots of departments had bucket-seat cars retrofitted with split benches for greater comfort, and there was some variety in engines, as the 351-2V (typically Variable Venturi) was the "performance" option, but plenty of cars saw police service with 5.0 power (2V/CFI/SEFI depending on year) and dual exhaust. It also has the heavy-duty frame (stamped from thicker sheet stock) and higher rate springs and swaybars (see mrltd's FAQs in the Suspension forum - also has factoids about stock wheels, etc.).

[gadget73]

1) You have a better geared rear than a police car. Many of those came with a 2.73 or 3.08. Police cars have solid upper control arm bushings where you have rubber, police got a 140 mph speedo, and the transmission pattern was P-R-N-OD-D-2 instead of P-R-N-OD-D-1. Some police cars also got an oil cooler. The front and rear bars on a police car are a little bigger, and the springs a bit stiffer. Its nothing terribly major though, the only bit of that police specific stuff I'd be personally interested in would be the larger rear sway bar. Also, as mentioned your car will be better appointed than a police car, which generally had nothing good for options.

3) The HPP got different axles in different years, so its possible his car is an open differential. ALso, if its got traction control, I'd almost expect an open rear. For whatever reason, Ford doesn't usually combine electronic traction control and a limited slip rear. Not sure if it works better with an open rear or what the story is.

[1987cp]

1) You have a better geared rear than a police car. Many of those came with a 2.73 or 3.08. Police cars have solid upper control arm bushings where you have rubber, police got a 140 mph speedo, and the transmission pattern was P-R-N-OD-D-2 instead of P-R-N-OD-D-1. Some police cars also got an oil cooler. The front and rear bars on a police car are a little bigger, and the springs a bit stiffer. Its nothing terribly major though, the only bit of that police specific stuff I'd be personally interested in would be the larger rear sway bar. Also, as mentioned your car will be better appointed than a police car, which generally had nothing good for options.

Thanks for mentioning that, I tend to forget the valvebody and oil cooler because this car doesn't have 'em anymore. It does, however, still have the power steering cooler (basically a big loop of hard line that runs in front of the radiator) and auxiliary transmission cooler.

I'm actually not all that enamored of the front springs on this car - I personally think they're a bit harsh. I occasionally toy with the idea of swapping in my 1/2-coil-cut wagon springs someday to try them out. The rear rides pretty nicely, though.

Also, I forgot - the HD frame includes a lateral brace in the far rear, just forward of the rear bumper. However, this feature is functionally replicated, and presumably then some, on any car where you install a frame-mount towing hitch.

Has anyone yet figured out any rhyme or reason behind which cars left the assembly line with the two bolt-on front crossmember braces?

3) The HPP got different axles in different years, so its possible his car is an open differential. ALso, if its got traction control, I'd almost expect an open rear. For whatever reason, Ford doesn't usually combine electronic traction control and a limited slip rear. Not sure if it works better with an open rear or what the story is.

I hope the HPP traction control was nicer than that on the original Mark VIII? Greg told me his Mark utilized an open rear and then the traction control system would simply apply the brake on whichever rear tire it deemed to be spinning excessively. Said something about going through a lot of right-rear brakes.

[crown vic muscle]

my 97 cougar had the traction control with an open rear. i can attest to the fact that it does apply the brakes to the wheel that spins. if it were a posi, it would wear out the clutches really really fast! whenever i drove that car i would turn that POS off and drive normally. the traction control made for some scary situations, you expect the car to do something and it does something completely different and limits the power and brakes on one wheel.

[gadget73]

thats how the traction control works, it uses the ABS system to apply the brakes on the wheel that spins in order to force power to the other wheel. I've never driven a car with TC, but I think I'd rather have a regular traction lock to distribute power for me, and modulate the gas to control wheel spin. I'll have to drive a traction control car sometime to see how I like it though.

[Glen]

I have 235/70 on stock rims. Works for me.

[TomO]

Thanks to everyone who responded. For the time being, I think I'll just keep my stock turbines and 215/70's, since there almost new tires. That'll give me some time to think about what I want to do as far as different wheels and tires, etc.

[Enigma]

I've run 235/60-15 on my stock wheels, no problem. Good ride, no mushies. Only .8" shorter overall diameter than stock, too.

[TomO]

Regarding the Crown Vic HPP, I hadn't thought about the fact that it could have traction control in which case -- as some of you have pointed out -- it probably would not be limited slip.

Do all traction-control cars have the ability to turn the traction control on and off? I'll have to look at the car again, but I didn't see any switch or anything to turn the traction control off. Maybe reading the owner's manual would help.