3:55 or 3:23?

[Thirty6fordguy]

Which rear end would you guys prefer in a Super Bee that sees quite a bit of Hiway driving? Tires are 27 tall, mild cam , 383. 727 TF transmission.

 

[WileERobby]

3.55 hands down

 

[HawkRod]

If you are using a stock transmission, then I would say 3.23.

My 70 RR has a 3.55, but I put a Passon 4 speed overdrive in it when I drove it across country. It is basically an A833 with 3rd and 4th swapped and an overdrive built in. It hurts acceleration some, but driving it on the highway is like a dream. Last year, I temporarily swapped back in my numbers matching 4 speed for a time, and I couldn't stand it any more on the highway, so I swapped the overdrive back in.

So if you are really going to do quite a bit highway driving and can swing it, put in the 3.55 AND an overdrive - best of both worlds...

My two cents worth.

Hawk

 

[Thirty6fordguy]

Why would you choose the 3:55? Is it higher?

 

[HawkRod]

Why would you choose the 3:55? Is it higher?

A 3.55 will cause you engine to rev higher at a given highway speed than a 3.23. On the other hand, a 3.55 will allow you to accelerate faster. So you need to pick your preference...

 

[Thirty6fordguy]

Good explanation. Also would my Super bee have the large yoke or small yoke? And will they interchange?

 

[VANDAN]

My '69 Super Bee was a 383, 4-spd, and had a 3:55 sure grip in it. The 3:55 was perfect for "all-around" driving, as my '70 Challenger 383, 4-spd, with 3:23 sure grip just doesn't have that off the line jump, but it will bury the speedo on the highway. Have a 3:55 for it, and I'm changing it out by the end of the year...

 

[WileERobby]

It's really a personal preference. For me, the small sacrifice of rpm' s at highway speed, are more than made up for it with the off-the-line jump with the 3.55's.

 

[2LGT2QT]

I recently changed from a 3.91 to 3.55 to help drop the revs for freeway driving. The difference in off the line acceleration was immediately noticeable...would not want to go any lower the 3.55.

At 75 MPH with a 1:1 drive ratio and 28" tire (275/60-15):
3.23 = 2900 RPM
3.55 = 3200 RPM
3.91 = 3500 RPM

 

[HT413]

You say frequent highway, but are these long trips? If you want to go on long road trips like good old Hawk, I'd go 2.76 or 3.23.

I hit the highway in mine but never more than 20 minutes and I don't mind going 55-60mph, so my 4.10's are just right.

 

[terzmo]

29 inch tall tires and 355's

 

[HT413]

Here's a cool tool that allows you a side by side gear comparison...

http://www.f150hub.com/tech/axle-ratio-comparison-tool.html

2400 rpm is a super comfy rpm, 2800 is borderline but I find it good for my short highway trips... 3000+ on the highway is balls to the wall and is a big reason why I get 7.5 mpg.

Here's a few options based on your choices...

 

[djais1801]

I recently changed from a 3.91 to 3.55 to help drop the revs for freeway driving. The difference in off the line acceleration was immediately noticeable...would not want to go any lower the 3.55.

At 75 MPH with a 1:1 drive ratio and 28" tire (275/60-15):
3.23 = 2900 RPM
3.55 = 3200 RPM
3.91 = 3500 RPM

my 72 Demon with a mild 340 has same rear tire size, 4spd and I am running 355's
cruising at 3000 RPM at 60mph

 

[Cranky]

Good explanation. Also would my Super bee have the large yoke or small yoke? And will they interchange?

You need to look and measure it. Is the car is totally original? The 3rd members in these cars usually were swapped out at some point in time in the last 48 years or so. Also, the factory didn't always follow it's own 'rules' for what parts should go into the car. If there was a hiccup on the assembly line, it wasn't all that unusual to plug in whatever that was available to keep the line going.

 

[Glenwood]

My 25.5" tire & 3.55 has my RB turning at about 3500rpm at 65mph. I plan to go to a taller tire and may very well drop it to a 3.23 since I have to spend at least 20 minutes on the highway in every direction, every time I take it out.

 

[roadrunnerh]

3:23

 

[Bruzilla]

On the other hand, a 3.55 will allow you to accelerate faster. So you need to pick your preference...

That's true, but only in relative terms. If you have like a 2.76, a 3.55 is a huge increase in acceleration, but if you have a 3.23 you're already accelerating pretty well, so the marginal increase in acceleration really isn't worth the extra gas costs in my opinion.

Go with a 3.23.

 

[rumblefish360]

I had 3.23's & 245/60/15's behind my 400/727. It was good on the Hwy. Long trips really wouldn't be an issue. Reasonable passing power.

When it let loose, I went to 3.55's. A slight jump in cruising rpm I did not find a problem. The off the line, get off the short Hwy. ramp into traffic was better by a little as expected. And well liked.

For me, on this crowed Island and limited open Hwy., the 3.55 gear proved advantageous and worth it. If I had wide open expanses of open road with the ability to travel at 70+ for extended times, the 3.23 would be my max. As it is now, I'd be lucky to travel at 70/75 for an hour.

 

[Ranger16]

I'd vote 3:23 as well.

 

[66Satellite47]

For a lot of highway driving 3.23 seems like the good choice. But a 3.55 seems like a pretty good compromise.