The fuel mileage at a certain RPM is determined by three variables. One is the speed on the highway (drag). Another is the friction loss of the drive train. The other is the efficiency of the motor at that RPM.
So at a fixed speed, the drag will be the same regardless of RPM. Friction loss will decrease at lower RPM. So we would think that running a lower numerical ratio will improve fuel mileage. It will if the motor operates efficiently at the desired RPM. Unfortunatly there are not many motors that are very efficient below 2000 RPM. Usually the best fuel mileage is obtained at the RPM where peak torque is obtained. A RV cam like a 255DEH will produce peak torque between 2000 and 2500 RPM.

You should gear your Lincoln to cruise at 70 MPH at about 2200 RPM. You can use an OD unit like Gearvendors, but that does add a little friction loss, or you can buy an adapter and get an AOD tranny, or just gear it right by changing the Ring and Pinion and/or tire diameter.

 

If you're looking for great mileage, sell the Lincoln and buy a Skoda.

If you want to enjoy the 6.6L you're rebuilding, don't try and make it into something it's not - fuel efficient.

2.47 gears in this car are about as low as you want to go. Anything numerically lower and you won't notice the torque of the motor, because you have no mechanical advantage to put the torque to the rear wheels. Think of it as trying to start a manual in 3rd gear every time.

If you want highway mileage, you need an overdrive. That allows you to reduce the mechanical gearing (and thus RPMs), once the vehicle has accelerated up to speed, and torque is no longer as important.

Switching ring and pinion shouldn't be hard. If the rear is a Ford 9", you can just pull a 3rd member from a junkyard. They're already set up (it's a dropout 3rd member), so you can just pull your axles, bolt it in your housing, and replace your axles. No setup required.

I would actually try and increase my gearing in this car, up to 3.10-3.25 range. Then get overdrive unit that works with your transmission, convert an AOD, or get a E4OD and run a stand-alone controller for it. Then at 60 (mph) your're running 1800 RPM - right where the 400 wants to be at that speed. But the difference would be in the acceleration - you will really notice it now.

All of the overdrive options are expensive, and will require fairly extensive modifications to your drivetrain. You might want to figure out your fuel savings prior to pursuing any of this, as you might find you need to drive 100,000km/year for the next 20 years to recover your costs.

 

where can i get a ring and a pinion, junkyards are not as easy around here...and how do I know i have a 9" rear. mu rear´s from a 73 mustnag with a 302.
I would like to go to 3.50-3.75 thanx...

 

for the Lincoln, not much can be really done to improve gas mileage. However, I wonder if an E4OD would fit? As for 9" rear ID. I could explain it, but I'll just give ya this link: http://www.kevinstang.com/Ninecase.htm

Oh yeah. Randy's Ring and Pinion sells the proper parts.

 

I think Havi is right, you are not going to get an E4OD to fit your tunnel. Probably have to mount the 400 over the front bumper to get the tranny to clear-----now thats a joke

All the add-ons add length to the combo and may make for a very short driveshaft. Besides, my experience is they are noisy and not smooth to engage. I had a richmond unit mounted to the tailshaft of a C6 behind a 460 (van). Did not like it at all, also not enough ratio, maybe new ones better of whatever brand.

Some others covered the gear thing, if you warm things up, you may want lower (higher numerically) gears. My opinion is that do what you can that is fairly easy, such as a simple gear change. Break out your calculator and see just how much money you are about to spend for anything else-----sure could buy a lot of gas with that amount.

Buy a 2 1/2 cylinder Yugo and do your driving in that

 

Thanx Havi,

It seems if i have the hump i should have a 9", I remeber seeing it on my rear, i will check tomorrow in the afternoon to be sure along with other stuff said in the article mentioned by havi, anyways acording to the article the only other possible one in my 73 tang is a 8", is there good stuff available for the 8" one? just in case im wrong bout me having a 9"....

also can you please point me the web page of Randy's Ring and Pinion .?...


thank you

 

http://www.ringpinion.com/

 

FOund it jejeje, instead of the other question, what do you recomend on my 408 turning 5k with the comp cam xe274h in my mustang 73 for stereet fun? I was thinking on 3.50 or 3.75, what do you think,? thanx

 

I couldn't really tell ya, but if your peak hp and torque is at a higher rpm, by all means go with the 3.75's.

 

ok, thanks. I'll look into it.

Buying a riding glovebox ain't the way.
I don't want to run it as good as such, but i DO want to squish every mile out of the gallon that i can with it...


The Electronic 4-shift i've been thinking about for a while, but IF it would fit, or made to fit, how does the computer stuff works to have it on my '79-er?
Electronics itself is no problem for me to install and/or understand, so there's no problem in that.
are there seperate computers available, and where do they connect to?
What kind of sensor's and so on?

 

oh, for the Yugo and Skoda funnyguys: i calculated it to more understandable terms. We pay $8.640 dollar for a gallon of gas...
Maybe that's more clear why i'd want a tad more efficiency and it's allowed to cost a few bucks...

 

Hello Steph.
What do you pay for propane/litre? Do you need to run on petrol (gas) at all? If you buy decent alloy heads, or put hardened valve seats and bronze valve guides in, should be able to run with propane 100%. Unless you are using the old style dual propane conversion set-up?
I used to have a 2.75 rear on my XD. For daily driving in traffic was a shocker. A 3.89 rear did wonders for performance, but a bugger on the freeway!
Craig

 

I run a 3.25:1 gear ratio with 28" tires. My motor will hit 3000 RPM at just over 70 MPH. My peak torque is at 4700 RPM, but who wants to drive with 434 cubes screaming at you all the time. My torque curve is flat enough to allow me to cruise at 70 MPH without a big fuel hit. I once considered an E40D, but discounted it due to the massive size. I didn't want to have to modify my tunnel to make it fit. I am using the old reliable C6.

If you want to change the ring and pinion, i suggest that you take the center section to a gear specialist. They require special tools and knowledge to set up properly.

 

I'd say that you are pretty close to where you want to be in the gear department. Lincolns were built for smooth operation at low RPM. Worst case would be to increase the tire diameter a little so you can run a litte faster at that RPM.

 

9" rears are stronger than 8" rears, but is having an 8" rear that bad to change it to a 9"? or will the 8" rear be as good? performance wise...