Better MPG with auto or manual?

[warpdriv]

So I am trying to decide between a NV4500 or 700R4 for my 4bt project.

Final Ratio RPM @ 70 (for my setup 3.70, 35s)
NV4500 .75 1866
700R4 .70 1742

So in theory, I will get better gas mileage with the auto. But auto are less efficient that manuals.

What do y'all think based on MPG?

Thanks,

 

[Diescipel]

wouldn't 5/100s of final drive ratio only make a different cruising on the highway at highspeed when the torque converter is locked up?

frankly, for a cruiser, I don't think it would be enough to make the difference and you would get better mileage with the manual. Actually, I bet it would be so close it makes no difference and the better question to ask on a cruiser is what will the rig be used for (DD, trail, crawler) and what tranny is best for said purpose.

so tell us more about your build and the intended use...

B

 

[warpdriv]

It's going to be a 60, SOA, 35s DD / Expedition rig. My 40 is not steet legal so I would like to build something that I can drive to an event or vacation, wheel it, and then drive home.

 

[Barry822]

In my opinion you will get better fuel mileage with the auto. For a few reasons. Manuals you tend to do more stop light racing. Autos allow for the turbo to stay loaded up which means your engine will be running more effieciently. With the 700R4 you also get the lowest first gear you can get in an auto, with the highest OD. If you get really into the 700R4 you can also get the torque converter to lock up in 2nd 3rd and 4th gear, which means you are driving a 7 speed. And with the 4BT you only have so much usuable RPM range. Just my opinion.

 

[UpsideDown]

Stop light racing will likely affect mileage in a small way... we're talking about a diesel here.

Also, sometimes a lighter load and slightly higher rpm can give better fuel economy. Remember that the situation with fueling and a diesel are different than with a gas engine.

And... the numbers almost never support better fuel economy for an Automatic, even if it has lock up.

I would also be concerned that your torque peak and revs for MPH don't match very well...

If you're really concerned about fuel economy, you'd likely be far better off with 16" wheels (higher pressures, stiffer casing=less rolling resistance and better fuel economy).

 

[Tapage]

I saw few days ago and B&M trans kit for TH700 not sure if aply to R4 so this kit contains a rebuild kit for sure and very interesting thing as lockup manual switch. You can lock up manual in all gears and the kit change your shifting point as your desirable point ..

I'm agree with auto box .. well maintained is better than manual.

 

[Martin White]

Although I'm not as mechanically able as many on this forum, one thing I am good at is reading and researching. I have yet to find a reference anywhere that would suggest a CRUISER would get better fuel economy with an auto over a manual. There are definitely other vehicles where an auto is better, but they are generally programmed specifically for the vehicle and are electronically controlled. So in this case I suspect the manual would get better economy, like all the cruisers I've read about. That's an executive summary of my own reading.

 

[crushers]

off topic:
the auto 81 and the manual 81 come VERY close to matching fuel milage returns, the lock up torque convertor is one of the big equalizers...
different drivers can equal different results though...
cheers

 

[Greg_B]

off topic:
the auto 81 and the manual 81 come VERY close to matching fuel milage returns, the lock up torque convertor is one of the big equalizers...
different drivers can equal different results though...
cheers

Arn't the final drive ratios different too on the manual vs auto HDJ81? On the highway the manual has to rev much higher to maintain the same speed...

Some much prefer the auto for this reason fwiu.

gb

 

[crushers]

that is true, never thought of that point...
thanks

 

[warpdriv]

This site got sent to me from the 4bt yahoo group:
http://www.bowtieoverdrives.com/index.shtml

Thought I would pass it along...