Ford Class C with 6 speed transmission

Hi,

I did go to taller tires. If I drive extremely carefully at 48 mph I get 12.5 MPG. If I drive 55 I get about 10.5 mpg. If I drive 65 I get about 7 mpg.

With the OEM size I got about 1 mpg less at each of those speeds.

I've driven the mountains with the taller tires and found no issues with power.

Be aware that new rims are needed if you go to a taller, narrower tire.

Ford is unable to re-calibrate the speedometer as the option to do so is greyed out for Vans. They can do it for trucks.

Gjac wrote:
Hi Phil, what was you MPG before and after the tire change?

My old'99 Ford F53 Class A chassis with the V 10 and 4 speed trans was doing about 2600 RPM at 60 mph in overdrive. What can I expect from a Class C ,E 450 6 or 5 speed at 60?

pnichols wrote:
I think that I've improved my motorhome's V10 fuel economy over what is possible with it's 5-speed 5R110W transmission by retrofitting it with non-stock tires that are larger in diameter. Going to a larger diameter tire makes all gears "taller" in any vehicle for improved fuel economy when cruising.

Since our Class C motorhome is a relatively small one for it's E450 chassis, I don't need the extra pulling power that the E450's 4:56 ratio differential provides, so I may as well get some improved mileage through use of larger diameter tires.

An E350 chassis has a 4:12 rear differential ratio, so larger diameter tires on it under a motorhome might make it lug down on hills a bit.

Hi Phil, what was you MPG before and after the tire change?

I think that I've improved my motorhome's V10 fuel economy over what is possible with it's 5-speed 5R110W transmission by retrofitting it with non-stock tires that are larger in diameter. Going to a larger diameter tire makes all gears "taller" in any vehicle for improved fuel economy when cruising.

Since our Class C motorhome is a relatively small one for it's E450 chassis, I don't need the extra pulling power that the E450's 4:56 ratio differential provides, so I may as well get some improved mileage through use of larger diameter tires.

An E350 chassis has a 4:12 rear differential ratio, so larger diameter tires on it under a motorhome might make it lug down on hills a bit.

carringb wrote:
The 6R140 has double overdrives, with the top ratio at 1 to 0.67, vs 0.72 for the 4R10/5R110, and was designed with fuel economy improvements in mind. One operator I spoke to found their new shuttle buses were seeing about 20-percent highway fuel economy. There were other improvements made besides the gear ratios, to make it more efficient. The difference probably isn't as dramatic in a motorhome because aero drag is much higher.

The V10 got the 6R140 for the 2016 model year, then it was added to the 6.2L V8 for the 2017 model year.

Good information. I had a 96 Jayco Eagle with a 460 and the E4OD. I had the Banks headers and if I kept my foot out of it I got 10 mpg. Now I have a 2017 Greyhawk with the V10 and 6 speed transmission and I still get 10 mpg, the big difference being the new rig is 10 foot longer and much heavier. I've been really pleasantly surprised with this excellent drivetrain. I had expected like 7-8 mpg. I also have an 03 box van with the V10 and the 4R100 and the mileage is horrible.

We had that 4 speed in our 2000 Four Winds, and it sorely needed a gear between 2nd and 3rd. When pulling hills, it was either screaming at 4500 RPM in second at 50MPH (or thereabouts) or lugging in 3rd for a few second before it'd drop to 2nd again....
Any time that thing saw a rise 5 miles away, it'd shift out of 4th, and it'd do only about 45-50 MPH on any significant grade.

If at all possible, get one with the 5 speed, or ideally, the 6. I understand I had that anemic V10 with that 4 speed as well - the newer V10s have better HP.

Our current ride, a 2016 Sunseeker 2250 on Chevy 4500, has a well-geared 6 speed coupled to the strong 6L V8. I can easily hold the speed limit on any hill, though I let it fall back as I'm never in a big hurry to get to the top.

The 6R140 has double overdrives, with the top ratio at 1 to 0.67, vs 0.72 for the 4R100/5R110, and was designed with fuel economy improvements in mind. One operator I spoke to found their new shuttle buses were seeing about 20-percent highway fuel economy. There were other improvements made besides the gear ratios, to make it more efficient. The difference probably isn't as dramatic in a motorhome because aero drag is much higher.

The V10 got the 6R140 for the 2016 model year, then it was added to the 6.2L V8 for the 2017 model year.

Gas mileage would probably not improve much if any due to the new transmission. It was introduced on the E series a year or two ago, if memory serves.

The gap between the top two (highway) gears is a good bit less wide on the new transmission, vs. the five and four speed ones which were basically identical in that particular regard. That alone would make for pleasanter driving in many circumstances.

I wish our older Class C had more than it's 4-speed but honestly the 4-speed does just fine. I doubt a difference in MPG would even be noticeable but it would give more options for up and down hills. An old friend has a Chevy pick-up with a 2-speed powerglide and even that is adequate.

At highway speeds no improvement because the top gear ration is no different.