Dave, if you are running a carb - have you measured your fuel consumption? Using a quarter tank of fuel by my gauge is about 8 gallons - the gauges are not very accurate, they just tell you when you are going to run out of fuel.
I'm using a Holley 600, with a brand new tank, and a NOS fuel sender. When it gets to empty, it's empty, it takes @ 70 Liters to fill, which is close to 19 gallons. I've run it pretty low, a few times, just so I could see how much it takes to fill it up (with a gas can in the trunk) I couldn't check actual odometer readings, since my speedo wasn't working for most of last summer. It's working now, so I'm going to keep a closer eye on it. Last summer, if I was doing 65 mph (with my GPS, and later with my speedo) it would run about 1800-1900 rpm. But I'm not one for driving a constant speed, if I lay into it, it takes right off. My AOD is far from stock, if that makes any difference. I'm interested in know more about the AOD with 4R70W guts, I have a 4R70W, but I don't really want to have to buy a computer to run it...
one year going to the...Gathering/Roundup...we drove 3300 miles in 11 days...gas milage was 22.5 MPG w/3:55 gears and Holley 600... Paul, did you do this...AOD-carb. research or did you read it on the net? "the two barrel is a good example of this. Running 3.0 gears you will never get out of the idle range of the carburetor." do we have a lot of these setup on here w/AODs?
Probably his AOD, he had more problems with C4's then he should have. His car spent so much time in the shop without a drivetrain in it because of the C4 that they forgot what kind of car it was and it came back with a chevy motor and transmission stuck in it.
yep...you need to know if the Guy at the shop is a Ford Guy or not before you drop your car off and tell him...to just..."fix it". ......
I have been building C4s and AODs for years. I had a lot of complaints from my customers who swapped AODs in to replace their C4s. They thought it was a transmission problem. After checking with those that were happy and those who weren't the difference was those who complained had stock rear gears. The guys that get the best mileage have ratios higher than 3.89:1 or are running EFI. I would say that my Years of experience qualifies as research but it wasn't like real research in that I didn't use a double blind testing situation. Just a preponderance of evidence pointing to cars that run in the idle circuit at low rpm use more fuel than those running above the idle circuit at the same speed. I have never seen any articles on the AOD saps using stock rear gears. Have you?
Customers are funny..... If you work on their cars and something doesn't work as they expect after it is always the fault of whatever was done to their cars. They thought there was a problem with the transmission when the transmission was fine but they couldn't get the "30%" increase in fuel economy that they thought they would. OK, we know that that would be impossible but people are funny that way. They thought that a 30% reduction in rpm would give them that much more fuel - not going to happen! They lost fuel economy instead and that I could fix with lower rear gears. Sometimes they got a few more miles per gallon but more often that not they end up with nearly the same mileage they got before the swap. The old truism comes to mind - it takes a certain amount of fuel to push a given load to a certain speed. You can reduce the rolling resistance, you can reduce the wind resistance and you can reduce the weight to get better fuel economy but changing the rpm (within limits) will not produce more MPG, especially if the mixture is richer than when you started.
I'd think the converter locking up would be one aspect of the AOD swap that will help with fuel mileage. ... I can see your point Paul. I've heard folks claim better mileage at a higher cruising speed. Could be they are getting the engine into a more efficient operating RPM
