Calling DRD57 - or was that Mr. Cheeto?

[C9]

A couple of years back you swapped the diff in your coupe and went from a 3.50 or 3.70 to a 3.25 or 3.00.

Seemed too that your mileage took a big leap in the mo bettah direction.

Which diff did you go to and what was the mileage improvement?

Reason I ask is, I have an unassembled new stuff 3.50 locker waiting in the wings.
With the thought that it would go into the 31 since it has 31 spline axles.
Too boot, I'll be running a smaller diameter tire (28" vs. 30.5") on the 31 than I do on the 32.

Been thinking seriously of getting a different ratio ring & pinion.

[Bib_Overalls]

I have a set of 3.25/1 Ford 9" gears (R&P) in the shop.  I'll make you a hell of a deal if you can use them.

I'm running 3.25s in my roadster.  So far as I can tell I got around 20 MPG on my recent trip to Springfield, MO.  I'm going to put  a pair of lsrger diameter tires on the rear shortly.  Should give me a little more squeeze.

[C9]

I have a set of 3.25/1 Ford 9" gears (R&P) in the shop.  I'll make you a ##### of a deal if you can use them.

I'm running 3.25s in my roadster.  So far as I can tell I got around 20 MPG on my recent trip to Springfield, MO.  I'm going to put  a pair of lsrger diameter tires on the rear shortly.  Should give me a little more squeeze.

Is the ring & pinion new?
Don't wanna be an elitist here, but I have everything new including the carrier proper - provided the bearings haven't rusted up - its been in the closet for a while....

(I've got an open 28 spline 3.25 carrier ready to bolt in.  Been thinking about using it in the 32.)

Seems like a 3.25 ought to be about right for the 31.
Might go to a taller tire after it's up and running.
How tall are your present rear tires?

[Bib_Overalls]

The R&P is used.  Fellow I know swapped them out in favor of 4.11s.  They have Ford marks.  They have been stored in a  Richmond Gears foam pack box.  

I'll measure my tires in the morning and send you the specs by e-mail.

[DRD57]

I ran the car for about a year with 3.50 gears. Then swapped to the 3.00's.

Mileage went up a couple MPG's, but I only check it occasionally.

As I got more comfortable with the car and fine tuning things I realized that the car ran the best and smoothest at about 2800 RPM's.

When I swwapped back to the 3.50's last summer the mileage didn't really go down but I found I was driving slower, keeping the RPM's at about 2800 on the hwy.  

Now with the bigger cam and bigger heads the engine seems to run the smoothest at about 3000 - 3200 RPM's. With the 3.50 gears and 1" shorter tires (27" vs 28") I'm still running about the same speed and still getting about 15 mpg.

[C9]

I ran the car for about a year with 3.50 gears. Then swapped to the 3.00's.

Mileage went up a couple MPG's, but I only check it occasionally.

As I got more comfortable with the car and fine tuning things I realized that the car ran the best and smoothest at about 2800 RPM's.

When I swwapped back to the 3.50's last summer the mileage didn't really go down but I found I was driving slower, keeping the RPM's at about 2800 on the hwy.  

Now with the bigger cam and bigger heads the engine seems to run the smoothest at about 3000 - 3200 RPM's. With the 3.50 gears and 1" shorter tires (27" vs 28") I'm still running about the same speed and still getting about 15 mpg.

Pretty similar to what I'm doing - on the highways anyway.
My engine seems to like running at 2900, gets real smooth there and it's hitting right on 70 mph at that rpm.

I probably ought to learn that driving this brick - aerodynamically speaking - at highway speeds is gonna use fuel no matter what.

Next car will have the same height windshield, but a lower top.
It'll be interesting to see if that helps.

Thanks for the info.