Gears?

[furious70]

I would buy a good used 3.23 center section and throw it in there to see how you like it. Probably find one for around $400-450 shipped if you're patient. Only replace axle bearings and such if needed.
Before I had my OD I ran 3.23 and 28" tires for years, best compromise imo.
I ran 3.91 and 28" tires, really a hoot around town but even 60 on a 2 lane got old.
Now I have 3.91 + 2.68 final drive, heaven.

 

[navajo denny]

That's good to hear, where did you buy the new gears?

I will find out had a mopar guy redo rear mine is a 8.25 and you have a 8.75 correct I will find out tomorrow

 

[Turboomni]

As I am just another bloke that wants everything, very,very good acceleration ,nice on the highway [isn't that what these cars are all about anyways?] and kinda good mileage maybe, I think anything over 3.23 or 3.55 is going make you think twice on your decision especially on the highway. My attempt at solving this without an over drive unit is keeping my 3.23 and stroking my 440 to 512 cubic inches. With a few hundred more ft pounds of torque from 2000 rpms and up than my tired low compression 440 I have now I hope to have both. Very good acceleration and highway happiness. If your engine is a bit tired and will need a rebuild in the future you can stroke a 383 close to 500 ci.
Just a thought.

 

[twostick]

3.23 is your best compromise and you will notice a big difference off the line compared to the 2.76 you likely have now.

If you are tempted to go for a 3.91, try driving around for a week in second gear. That is pretty close to where a 3.91 will be in drive. Fun around town and maybe even a little better on fuel. On the highway it will get old fast.

Kevin

 

[furyusvip]

For pure simplicity, a set of 3.23 will wake up the off line acceleration of a 2.76 geared, 4,000lb car. Like others have said, this is the EASIEST way to improve your car without major modifications.

 

[71Polara383]

For pure simplicity, a set of 3.23 will wake up the off line acceleration of a 2.76 geared, 4,000lb car. Like others have said, this is the EASIEST way to improve your car without major modifications.

How much will that hurt highway MPGs making that jump Guy? Would 2.94 to 3.23 be noticeable?

 

[73Coupe]

If you have 2.76 gears in there now and getting rid of them, I'll take 'em for a spare set....!

 

[furyusvip]

How much will that hurt highway MPGs making that jump Guy? Would 2.94 to 3.23 be noticeable?

your engine speed would increase about 250 rpm at 70 mph with a 2.94 to 3 23 gear swap. It might not be a huge difference, but depending on whatever else you plan on doing to your car (Whiplash cam, Increased stall speed) it could be a nice improvement without killing your highway mpg

 

[furyusvip]

https://www.randysworldwide.com/calculators/rpm

this has a lot of simple calculations and help a bit when trying to sort a package out

 

[twostick]

I used to have a 79 F100 with a 300 inline, stick with 2.75's. 10 MPG was as good as it got. Vacuum gauge at 65-70 showed 10-11 inches. I swapped in a set of 3.50's and I forget what the RPM jump was but it was considerable but the fuel mileage jump was also considerable. 15 MPG or better depending. Vacuum gauge at 65-70 was 15-16 inches and a lot less throttle to maintain it ergo the higher vacuum reading.

Kevin

 

[413]

Thank you for that example! This is exactly why I don’t like those 2.40-2.70 gear ratios. They take you below the power band and kill the torque.

Gears do much more than set your highway cruising RPM

 

[73Coupe]

I used to have a 79 F100 with a 300 inline, stick with 2.75's. 10 MPG was as good as it got. Vacuum gauge at 65-70 showed 10-11 inches. I swapped in a set of 3.50's and I forget what the RPM jump was but it was considerable but the fuel mileage jump was also considerable. 15 MPG or better depending. Vacuum gauge at 65-70 was 15-16 inches and a lot less throttle to maintain it ergo the higher vacuum reading.

Kevin

Intriguing.... so higher RPMs yet better economy? Hmmm....

With the higher gears that were swapped out, I can interpret it as lot of your fuel was dumping in there with the more open throttle and not making any difference at that RPM...?

 

[furious70]

A 2.76 is still a good gear for a BB c body with stockish cam.
A truck like that probably had 30" tires.
We switched 3.55 for 4.10 in 5.9 magnum truck and mpg was a little better too. It had 31" tires

 

[413]

A 2.76 is still a good gear for a BB c body with stockish cam.
A truck like that probably had 30" tires.
We switched 3.55 for 4.10 in 5.9 magnum truck and mpg was a little better too. It had 31" tires

Does that truck have overdrive?

 

[furious70]

Does that truck have overdrive?

Yes

 

[B-Rode]

I'm leaning toward 3.55, my RPM @ 70 mph will be a little over 3000. A little quicker on the low end than 3.23 and not nearly as annoying on the highway as 3.91

 

[Turboomni]

I'm leaning toward 3.55, my RPM @ 70 mph will be a little over 3000. A little quicker on the low end than 3.23 and not nearly as annoying on the highway as 3.91

Sounds like a plan and let us know your thoughts of it.