Appears that if you aren't towing super heavy the 3.55's would be a good choice. They are getting decent MPG in the 14-15 range.

 

That's pretty awesome . . . . .

 

14-15 mpg Towing or unladen?

 

Can anyone offer more info on the 7.3 w/3.55’s?

Also, in the OP 4.10’s are shown in the spreadsheet. Pretty sure this is NOT an option with the 10 speed?

Thx, Bill

 

Unladen on the reports I've read.

 

That’s what I get on the highway with 4.30s. Welll, as long as I’m easy on the throttle.

 

Something to think about the effect of gear ratio chosen.

 

I picked the 3.73 gears. Running 78~80 on our first road trip we averaged 12.6. That was Abilene TX to Fort Worth for a day trip to the Summit warehouse and general putting around, dinner, etc. About 380 miles total run that Saturday. This is a 350 DRW XLT, crew, 8' bed, 4x2, camper pkg. Have not weighed it yet. Around town sometimes see 13ish. Pulled 12,000 with it last weekend - 60 sq/ft frontal, 34' x 7.5 tall box trailer, around 12K lbs, in a 20+ MPH crosswind. Ran about 63~65 because of the high wind. Got pushed around quite a bit as the track trip is east/west and wind was out of SSE. Clocked 6.5 average with that. Opted not to go 4.30 because we will be using this truck for some daily stuff, picking up grand kids & groceries and run primarily in Eco mode.

 

That is encouraging for a dually. Thx for posting...

 

My observations have been that the 10-speed transmission has made rear gear selection not really all that important unless you're going with some really extreme tire size.
If you need more first gear reduction than 1st and a 3.55 rear with a standard tire diameter, you're pulling more than you can sensibly handle with a 7000 lb.ish pickup.

 

This is something one should think about when choosing a rear axle ratio for your situation. The RPM spread between gears is greater when you use a taller gear ratio(3.55 is taller than 4.30). If you think you're going to tow fairly heavy and use all 10 gears with a 3.55, you may be in for a surprise. This is my third Ford gas with 4.30 gears(2 -V10, 1 -7.3) and if 4.56 gears were offered I would have got them. I bought my truck for short commutes and towing, mileage was not my first concern.
I don't care what gear you get, but there will be no 'Cry Buckets' issued if you're not happy with the towing performance with a tall gear.

 

You are incorrect in your assessment that the rpm drop is determined in any way by the rear gear ratio. the rpm drop at the shift is dictated by the ratio change in the transmission only.
I have a new 7.3 with 3.55's and do tow.......and it works just as I assumed it would in comparison to previous trucks with various rear gear/ transmission combos.

 

I didn't say anything about drop, I said, 'spread'. Towing every gear with a 3.55 will need to go a higher speed before it can shift to the next gear up to be in torque than the same truck with a 4.30. Another example would be towing in tenth gear @60 with a 3.55 truck and RPM's would be 1800, with 4.30 2300. The 3.55 geared truck may not be able to hold tenth because it's out of the torque range. The RPM's are just examples I don't know the actual RPM.

 

Just a difference in terminology. The "spread" determines the "drop" in rpm.....no, the 3.55 will not go to any different engine speed (rpm) till the next shift vs. the 4.30.... a trans ratio difference is a trans ratio difference and the rear gear ratio has no effect on that (with the exception of a loose race type torque converter, but we're talking stock essentially almost always locked converters here) ......and of course the different rear gear will change the rpm that the downshift occurs from 10th...but from then on down, they will be the same spread with either rear gear.
At WOT or a given throttle position, the transmission shifts at whatever the rpm shift point that it is programmed to shift at........whether a 3.55 or 4.30 gear.
The different rear ratios difference will only show up on the initial pulling ability to the top 1st gear and the top speed.(assuming no top speed limiter)

 

Maybe this will make it clear. It's an example of the effect on speed comparing 3.55 vs 4.30 with all things being equal. Ford would not have offered the 4.30 if it didn't make a substantial difference in towing. Look at the tow guide for F350 fifth wheel/gooseneck if you want further proof. You might look on YouTube and check the TFLTruck video with the 2020 Chevy 6.6 where the driver stated I wish this truck had a 4.10 rear instead of the 3.73. Ford sent a 7.3 with a 4.30 gear for that test and the truck was 2+ minutes faster up the hill than the Chevy towing the same load.

https://www.tremec.com/calculadora.php
TKO-600 .82OD

RPM 5200
Axle 4.30
Tire 33"

Trans
2.87 --------Speed 41.37
1.89-------- Speed 62.82
1.28---------Speed 92.75
1.00---------Speed 118.72
0.82-------- Speed 144.78


RPM 5200
Axle 3.55
Tire 33"

Trans
2.87---------- Speed 50.11
1.89---------- Speed 76.09
1.28---------- Speed 112.35
1.00---------- Speed 143.81
0.82-----------Speed 175.38