Not all of them do.

A firm wrist can handle a car as it was originally made, no modifications needed.

Because all you limp wrists cried about the noise.

Here's a clue. MoPar had OD trans in the 40's. Not like it's something new.

Thats a negatory there Ghostrider. Reduced RPM @ cruise equates to lowered emissions and improved mileage
every.
single.
time.
Overdrive has been enhanced with lockup convertors for the same reasons.

Ba.... Its all good if people like OD trans, obviously I like the old deep geared 1:1 stuff and I can drive slow until I need to drive fast and I could not give a --- about the cost of gas.

I live in the dry heat, if it hits 40% humidity im drippin so I do understand the ac part also.

One day I will give in, but I hope its not soon.

Can't believe how little the 3.55-1 is mentioned here. In a thread about 3.91's.

In the days before OD, ALL ratios were a compromise in a car driven both in town and at speed.

The 3.55 (3.54 for you more fortunate folks) was/is a GREAT multi-purpose gear!

so keep the stock 391 and trailer it?

Had a car for a while with 4.10:1 gears and 26" or so tires Also had no PB or PB but it did have 4 wheel drums,was my daily driver and went for carshows and such everywhere and the only thing i would have changed on that car if i had keept it would have been discbrakes in the front. Sure i wasnt going fast on the highway but no problem driving the posted limit even thought it was alitle hard on fuel on highways.

And not one limp wrist cried about worse mileage and emissions. The cried about "the engine screaming as you tootle along in the right lane getting passed".

Engines also wore out faster before overdrive.

The stock 318 in the D100 I mentioned before would not keep up with traffic with the pedal to the floor.

My first 69 SuperBee had 3.91s back in '74 and 3.91s have been my go-to gears ever since. Even today, my Cuda has 3.91s. But now, it also has a 518. So blasting down the hiway at 75 or so is no big deal......for me or the car.

3.91s are a lot of fun but are very hard on the engine on the hiway. I have popped more than one big block screaming down the hiway. But that was back when these cars were disposable and I could go to the local wrecking yard and pick up another 440, swap my parts to it, and go beat on it some more.

Today, blocks and stuff are harder to find, more expensive, and I am older and lazier. So, no 3,000 or 4,000 RPM screaming down the hiway for my stuff anymore. It may take it.....for awhile. But there is no doubt that it is hard on the engine. And we have choices now that we didn't have then. We can enjoy 3.91s and have reasonable engine speed on the hiway. Kinda like having your cake and eating it, too.

It's 2018, not 1974.

lol, that wasn't it's job. Imagine that same ride with a /6. Wee.

As for wearing out faster, more likely it had to do with the rings used and the oil formulations than OD. I still have the 318 out of my 87 Diplomat, 200k+ miles, bores look pristine. Moly rings, good oils, regular maintenance. No OD. back in the musclecar days, well oils sucked and cast iron rings.

If you are taking the time to ask then I believe you would be happier with 3:55. I had an E body with 440, 29.5" tall rear tires and 4:10s. I was not happy on the highway. Holding everyone up in the right lane.

I have 3.54 gears in my pile,and was thinking about switching up to 4.10s for racing.
Will my wrists become any stronger?
If Passon could kick out those 5 speeds he could sell a bunch.

I ran 4.10's for years in my wagon with 28" tires. I finally had enough of slow lane cruising and the engine singing above 3k. I swapped in 3.55's and my only question was why didnt I do it sooner! It made driving everywhere much more enjoyable. Granted, it did also have a healthy BB stroker, so still plenty of tire roasting at will . But w the 3.55s, I could actually keep up with the majority of highway traffic for once, without buzzin the heck out of it. Prior to the 4.10s I had a Charger with 4.56's, and yes I see the pattern of gear ratio change with my age .

At hiway speed, the difference between 3.91s and 3.55s is a little over 300RPM. That isn't that big of a difference.


http://www.wallaceracing.com/calc-gear-tire-rpm-mph.php

Don't know if it's possible or not, but if the OP was able to run a tall tire on his Wagon, say 29 inch or better it mite not be to bad.

That was my first thought. Approximately 10% difference. Not worth it in my opinion. There is no gear ratio available that will allow you to cruise at 1500-2000 RPM like you are used to in modern cars with 2 overdrives and lockup converters.

Back in the late 60's early 70's many muscle cars from Ford. GM. and Mopar came with 4.10 gears and 26" tires. However a 383 Fury Wagon was not then, is not now a muscle car. It probably had a 2.93 originally. People drive faster now than in 1967. with a 2.93 gear at 75 mph the RPM will be 3000 plus but with no tach and a quiet exhaust system who noticed? 3000 RPM is not going to hurt a 383 unless it is already hurt.

The way I see it a 2.93, much less a 3.55 will not get you were you want to be. Several people have suggested an overdrive transmission. That is the only way you are going to cruise at 70-80 MPH at comfortably low rpms.

ME? 4.30s with 28" tires. Has only been on the interstate longer than 10 minutes at a time once in 20 years. If I ever get around to switching to a Dana it will probably get a 4.10.

I ran a D200 PU back in the day. All over the place with a lot of highway miles. 4.10's and 29" tires. It did OK on the highway. I would cruise 70 and sometimes 75 max. It was probably turning 3300-3500 RPM on a sustained basis at higher speed. That is as much as I would want to run and even then noisy even with turbo mufflers.

With car size tires (25-26"?) I think 3.91 would be too much. Also speeds are higher now.

My current classic PU runs 4.10's and 31" tires. OK to 70-75 MPH and spinning pretty well at that speed. As much as I want.

My '70 Challenger ran a 318 and 3.23 as original with 24-25" tires. The original powertrain did surprisingly well. Decent acceleration and OK on the highway. Now runs a 496 and still 3.23 rear. Also OD transmission. It runs well.

If highway driving is part of your plan, I would suggest a 3.23 rear. It will do fine on the highway and the 383 should handle it fine at low speeds. Plenty of go.

Got 4.30's in my Charger and they're fine cruising around 70mph. People magically move over when I come up behind them for some reason. Still, in the next few years I'll build a 400 based stroker and swap in my 3.91 pig. I think that will do for anything less than a cross country tour. YMMV...….

Back in 68-70 my 64 Plm had 2.76 and a 4 speed (a little hard on the clutch) oval sprint track tires on 15 inch mag wheels, kinda tall and had to massage the well a little. Even at 80 mph it was still under 2000 rpm. Back in those days I knew where the radar traps sat so we went whatever mph we wanted. The 70 Z would run 3000 at 60 but I have no idea what gear it had, buzzed around the 95 interstate 3500-4000 or more all the time. To get a ticket one had to be real stupid, not like today.