Which rear end to order?

[Joeyd9590]

Good morning,

 

I’ll be ordering my first SD in January. I currently have a 32’ travel trailer but want to be able to upgrade to a 5th wheel in a few years so I’m going to order a F350 6.7. What do you guys recommend for the rear end? I think I’m going to order an XLT with the premium package. Any other build info you could recommend, I’m very open to suggestions. 
 

Thanks!

[mattdm]

how big of a fifth wheel are you looking at? are you going to be using the truck for anything else other then towing? 

A 4.30 is the best gearing for towing heavy, but its a trade off of fuel mileage and driving comfort when you are not towing. Most people are happy with a 3.55 or 3.73 for a nice mix of towing and daily use.

You should also consider a long bed for fifth wheel towing as it will make towing it that much more comfortable, but again its a trade off if you also plan to daily drive the truck a long bed truck can be a beast in town.

Edited November 28, 2021 by mattdm

[Joeyd9590]

21 minutes ago, mattdm said:

how big of a fifth wheel are you looking at? are you going to be using the truck for anything else other then towing? 

A 4.30 is the best gearing for towing heavy, but its a trade off of fuel mileage and driving comfort when you are not towing. Most people are happy with a 3.55 or 3.73 for a nice mix of towing and daily use.

You should also consider a long bed for fifth wheel towing as it will make towing it that much more comfortable, but again its a trade off if you also plan to daily drive the truck a long bed truck can be a beast in town.

We won’t be looking to upgrade for another 3 years probably but I’d guess it would be around 15k max. Truck will primarily be used for towing but we do use our current truck for family things but that’s only a few thousands miles a year so not a lot. I just want this truck to be capable to tow what we later so we aren’t upgrading truck and trailer. I was leaning towards the 3.55 

[Ford truck guy]

I have 3.55 on my 2020 F350 SRW.. I BELIEVE that IF you want the 3.73, you need to change to the 7.3 ??  

 

I tow a 42' fifth wheel that has a LOADED weight of 16,500# and am within ALL of my weights, barely, but at MAX.... The main reason I didn't go to DRW is this truck is also my PLOW truck, DRW's just are not great in snow......

[Rangers09]

2 hours ago, Joeyd9590 said:

We won’t be looking to upgrade for another 3 years probably but I’d guess it would be around 15k max. Truck will primarily be used for towing but we do use our current truck for family things but that’s only a few thousands miles a year so not a lot. I just want this truck to be capable to tow what we later so we aren’t upgrading truck and trailer. I was leaning towards the 3.55 

 

I towed a 41' 5th wheel with a 2013 F-350 SRW 6.7 with 3.55 gears. Probably did about 30,000 miles with many of them in the Rockies. No issues on the long 8 - 11%+ grades, just took it slow. I did upgrade to a F-350 DRW 6.7, which came with 3.73 gears. With greater payload we could load the 5'er to 16,500 lbs and it was definitely easier in the mountains.

 

A SRW with 3.55 is good for the current trailer, but if upgrading to a 15K 5'er, with about 3K pin weight, you may also wish to consider a F-350 6.7 DRW, Last time I checked the F-350 6.7's the gearing options were 3.55 or 4.1, at least with Ford Canada. If driving in the mountains, I would opt for a F-350 DRW 6.7, with 4.1 gears.

 

For Long Box/Short Box, I could survive with a SB with our 5'er, but why take the risk, so I will only order a CCLB. 

[GAP338]

With the 10 speed and 6.7 I don’t see any reason to go slower than 3.55 gearing. We pull a 25k seed tender with absolutely no issues power wise.  When not hauling you’ll enjoy the better mileage. 

[road turtle]

There was a big write up awhile ago (March '21) that I used to go with 3.31.  Essentially, the new 10 speed lowers the starting ratio to the equivalent of 6 speed trans with 4.30.

 

I'm pulling and overweight 30' 5th wheel with F350D CCLB 3.31 FDR.  Trailer GVWR is 13,400, and in full travel mode, I'm just a little over 15k.  I do have upgraded trailer axles, so from that standpoint I'm good.  I have zero issues pulling with the 3.31 gears on my first trip from MI to FL.  Acceleration is plenty acceptable.  The one time I had to put my foot into it, it responded quite well.  I was entering a busy freeway that had an uphill on ramp, and wanted to get up to speed with a minimum of disruption.  I've seen the trans even getting into 10th gear on flat sections of freeway.

[Lee2021]

what @road turtleis the same as I found.  The 10 speed is a game changer and let ford put in a much lower 1st gear and a higher 10th gear compared to the 6 speed.  Frankly, either will work fine with this large spread.  If you choose the 3.31, you will have a lower 1st gear with the new 10 speed than the 6 speed connected to 3.73.  Conversely, if you choose the 3.55 in the 10-speed you will have essentially the same overall top gear as the older 6 speed in 3.31 gears.  For me, I like the lower RPM top gear cruising of the 10 speed in 3.31 gears, AND having better low speed power that this combo gives me compared to the 6 speed in 3.73 gearing.  Put a different way, See below how the new 10 speed with 3.31 covers more than the range of the 6 speed in 3.31, 3.55, and 3.73 combined.

 

From @dirthawg in a different forum back in February:

6R140.....1st 3.97 2nd 2.31 3rd 1.51 4th 1.14 5th 0.85 6th 0.67
10R140...1st 4.61 2nd 2.91 3rd 2.13 4th 1.77 5th 1.51 6th 1.27 7th 1.00 8th 0.85 9th 0.68 10th 0.63

Doing some math we get the following final drives.

6R140 with 3.31 gears..........1st 12.82 2nd 7.64 3rd 4.99 4th 3.77 5th 3.17 6th 2.21
6R140 with 3.55 gears..........1st 14.09 2nd 8.20 3rd 5.36 4th 4.04 5th 3.01 6th 2.37
6R140 with 3.73 gears..........1st 14.80 2nd 8.61 3rd 5.63 4th 4.25 5th 3.17 6th 2.49
6R140 with 4.30 gears..........1st 17.07 2nd 9.93 3rd 6.49 4th 4.90 5th 3.65 6th 2.88

10R140 with 3.31 gears........1st 15.25 2nd 09.63 3rd 7.05 4th 5.85 5th 4.99 6th 2.21 7th 3.31 8th 2.81 9th 2.25 10th 2.08
10R140 with 3.55 gears........1st 16.36 2nd 10.33 3rd 8.20 4th 6.28 5th 5.36 6th 4.50 7th 3.55 8th 3.01 9th 2.41 10th 2.23
10R140 with 3.73 gears........1st 17.19 2nd 10.85 3rd 7.94 4th 6.60 5th 5.63 6th 4.73 7th 3.73 8th 3.17 9th 2.53 10th 2.34
10R140 with 4.30 gears........1st 19.82 2nd 12.51 3rd 9.15 4th 7.61 5th 6.49 6th 5.46 7th 4.30 8th 3.65 9th 2.92 10th 2.70


 

[Joeyd9590]

Awesome info guys. Much appreciated! Glad I found this forum. I was messing around with different build configurations earlier. When building a 250 with the 3.55, it adds on the high capacity tow package which, correct me if I’m wrong, would make it equivalent to the 350? Would this package also raise the payload for the 250? I still think I’m going with a 350 for my future plans, but was curious is that changes any of the numbers for the 250. 

[sjmcken81]

1 hour ago, Joeyd9590 said:

Awesome info guys. Much appreciated! Glad I found this forum. I was messing around with different build configurations earlier. When building a 250 with the 3.55, it adds on the high capacity tow package which, correct me if I’m wrong, would make it equivalent to the 350? Would this package also raise the payload for the 250? I still think I’m going with a 350 for my future plans, but was curious is that changes any of the numbers for the 250. 

Yes and no, with F250 HCT.

 

 Your gvwr will increase from 10k to 10.8k, so payload will be same/similar to an F250 gasser.

 

Here in Virginia, once you cross 10k gvwr, you get taxed the same as an F350 with 12k-ish (diesel) or 11.3k (gasser) gvwr, so might as well get the F350 with the higher payload.

 

So, even though the F250 HCT can tow more and has 3-inch receiver, payload is still at or under 3k, while the F350 should be closer to 4K payload, dependent on gvwr and options.

Edited December 1, 2021 by sjmcken81
Clarification

[sjmcken81]

Another option is F250 HCT with Tremor package.  An F250 Tremor has the same rear leaf package as an F350, so it’s basically a derated F350…legal payload still less, but really is basically an F350, less the higher payload sticker.

 

It’s one of the reasons why we ordered an F250 gas Tremor.