I can't drive - SEVENTY FIVE! Or can I?

[Daniel Romero]

I've got a question that probably shows my lack of mechanical know-how, but I don't mind looking dumb so I'm going to ask:

Are these big, old Chryslers ok to drive interstate speeds of 75 or higher for long distances? This is of course only in situations where the car is mechanically sound. I ask because they were made when highway speeds were 55 mph. I want to make trips to Denver (or further) which is 90 miles one way but it sounds like I need my rear end rebuilt in my '73 Fury and I want to take gear ratio into account if I end up needing new gears. Also, I'd appreciate any advice on what I should look into for gear upgrades, please!

 

[detmatt]

I've put thousands of highway miles on my Imperial, these cars will handle today's highway speeds and then some and most of them are already geared appropriately for it.

 

[Zymurgy]

I have rebuilt all the suspension and steering box and my '66 is solid at any highway speed. I wouldn't hesitate to run it all day long.

 

[Big_John]

I've got a question that probably shows my lack of mechanical know-how, but I don't mind looking dumb so I'm going to ask:

Are these big, old Chryslers ok to drive interstate speeds of 75 or higher for long distances? This is of course only in situations where the car is mechanically sound. I ask because they were made when highway speeds were 55 mph. I want to make trips to Denver (or further) which is 90 miles one way but it sounds like I need my rear end rebuilt in my '73 Fury and I want to take gear ratio into account if I end up needing new gears. Also, I'd appreciate any advice on what I should look into for gear upgrades, please!

Actually, they were built back when interstate speeds were 65MPH most places, 70MPH in others.

Late in 1973, the feds mandated 55 MPH across the country in an effort to save gas.

So... The cars were built for these speeds. I'm pretty comfortable in my 70 300 Vert at highway speeds, although the convertible top lifts up about 2" off the bows at 80+.

 

[Fratzog]

Highway speeds are no issue with these cars. Aside from being sure it is mechanically sound also check the date code on your tires.

 

[Daniel Romero]

This is great news! I've been wanting to go road tripping in my Fury since I've had it but haven't had the funds to even plan for it till now. I'm going to get my rear axle rebuilt and after that's attended to I'll be good to go!

 

[Davea Lux]

This is great news! I've been wanting to go road tripping in my Fury since I've had it but haven't had the funds to even plan for it till now. I'm going to get my rear axle rebuilt and after that's attended to I'll be good to go!

You probably will find that your car will have 3.23 gears in it as they were the most common. If the rear end has not previously been rebuilt, it will have a metal tag on a third member housing bolt that will display the gear ratio. I would suggest pulling the axles before tearing into the third member as wheel bearing failures were more common than third member failures. (this assumes you have an 8.75 rear end) Also there is a screw type end play adjustment for the rear axles that can cause a lot of weird noises if it is not adjusted properly (the rear axle ends bank off each other and clank). Also a good time to check the oil in the rear end and change it if it looks degraded. Also check the U-joints.

Dave

 

[Davea Lux]

I've got a question that probably shows my lack of mechanical know-how, but I don't mind looking dumb so I'm going to ask:

Are these big, old Chryslers ok to drive interstate speeds of 75 or higher for long distances? This is of course only in situations where the car is mechanically sound. I ask because they were made when highway speeds were 55 mph. I want to make trips to Denver (or further) which is 90 miles one way but it sounds like I need my rear end rebuilt in my '73 Fury and I want to take gear ratio into account if I end up needing new gears. Also, I'd appreciate any advice on what I should look into for gear upgrades, please!

Most of the big Chryslers will have an 8.75 rear end and 3.23 gears. The Polara and Fury police cruisers ran this same combination and were easily capable of 100mph or higher all day long. The big thing to look out for on a big car is to be sure that your tires are up to the task. The Polyglass tires that came standard on most Mopars in the early 70's were notorious for seperating sometimes with catastrophic results. I had several memorable failures running the desert in eastern Oregon. Not likely you would still have any of those but check your tires so see what the speed rating is. Many current radials are not designed for high speed usage especially in high temperature areas.

Dave

 

[SPF Required]

?.....also check the date code on your tires.

Not wanting to steel the thread here, but I am curious about this. I am about to get my 68 300 back from the mechanic after about 6 years parked in my garage. About 2 months before dry docking the boat I got new radial tires on the car. Then she sat. Now I am about to start driver the car again and I a reading all sorts of stuff about tire expiration dates. Mine still look brand new, but they are technically 6 years old. Is this a real issue, or just Brilliant marketing as a way to sell more tires?

 

[The Horvaths]

I road trip my cars a lot. Bring tools. You will break down. That is the mindset you should have anyways. Yes these cars are fine to drive at "high" speeds, just keep your ears and eyes open.

 

[65 500]

If your rear diff. is limited slip don't forget to use the correct limited slip additive, or a gear oil that already has it in it.

 

[1978 NYB]

I've driven my 1978 NYB from Baltimore to Green Bay several times at 80+ mph with no problems at all.

 

[Gerald Morris]

I drove Mathilda up to Coolidge last fall to work the (S)Election. She did 86 mph coming and going, though on (S)Election night, returning, I had a blowout at ~ 78 mph that mildly perturbed me, and caused the millennial in the back seat to soil himself a bit. Being a rear wheel, when the rubber blew Tilly wallowed a bit but otherwise handled beautifully.

SO, my 51 yr old 66 Newport, loaded with 3 men averaging 190 lbs each, or ~570 lbs, cruised along around 78 mph, getting up to 86 when passing 18-wheelers, and made it safely to the roads shoulder when a rear tire blew out while I was starting to speed up to pass another trucker.

Safer than PLENTY modern crap! I run straight drum brakes, no booster, 1 cylinder on the master. Easy to work on thus. Have Faith in Mopar bro.

 

[Gerald Morris]

I road trip my cars a lot. Bring tools. You will break down. That is the mindset you should have anyways. Yes these cars are fine to drive at "high" speeds, just keep your ears and eyes open.

ALWAYS bring tools and common parts! Rubber stuff, bearings, points, wire, fluids and such. Hell, you have 6 feet of trunk to put it in!

 

[Zymurgy]

Not wanting to steel the thread here, but I am curious about this. I am about to get my 68 300 back from the mechanic after about 6 years parked in my garage. About 2 months before dry docking the boat I got new radial tires on the car. Then she sat. Now I am about to start driver the car again and I a reading all sorts of stuff about tire expiration dates. Mine still look brand new, but they are technically 6 years old. Is this a real issue, or just Brilliant marketing as a way to sell more tires?

Today's tires are crap, however I personally think you will be fine so long as the tires didn't sit in any water. I would still take a tire off and check down between the tread for cracks.

 

[mr. fix it]

my 318 poly tends to burn oil up internally when I do this for extended periods of time at 75+mph plus the fuel mileage drops pretty hard as well

 

[BIGBARNEYCARS]

75 iz ah minimum starting speed down in this country or you'll get run over. 55 to 75 in the residential neighborhoodz with a One Car Gap 'tween you and the one behind you 'cuz you ain't movin' fast enough

 

[GJS]

I ran a top of 75 mph across Canada with a trailer in tow and never had an issue... well till I neglected to look at the temp gauge because I was excited to be in Montreal and she over heated and ate a wrist pin .. but that wasn't her fault.

Eyes on the road, hands on the wheel, leave good distances and be ready to feather that brake pedal .. she'll do 75 easy.

 

[Snotty]

A car does not know what year it was manufactured, nor what the speed limit is. Even so, the National Speed Limit was reset to 55 nation-wide on January 1, 1974. By then it was claimed to have been done so to save gas; the actual reason for the legislation was to save "lives." Too many people were dying on the Interstates in those days. The first OPEC Embargo changed the reason for its institution.

Your car can run all day at any speed you want it to provided: you've maintained it well, the tires are good, it's safe to do so, and your rear-end gears are not in the 3.55 or higher range. I've driven my Newport at 80 many times, including a drive to Sacramento last June. It was built to do so; so is your Fury. Enjoy it!

 

[rapidtrans]

Our c bodies were designed during the 70 mph freeway era before the 55 mph joke. "C" bodies in good condition or when new can and did cruise at 80/85 straight down I-75 to Florida and back.