Ford F-350 axle ratings

[jpjulian]

We purchased a new Excel Winslow 31IKE last October. It has a 17,500# GVWR. Our F-250 diesel pulls it just fine but a trip to the scale yesterday shows we are 240# over our RAWR of 6100#. I can not find a dually, Ford, GM or Ram, anywhere in our area so am considering a SRW F-350. Problem is those available have axle ratios of 3.31 or 3.55. Not Ideal nor either the GVWR of 11,500#. Those of you who have a Ford F-350 SRW 2013-2014 model year, what is your rear axle rating and with what axle gear ratio?

Thanks

Joe

[BB_TX]

ah64id wrote:
.......

What if the 250/350 uses the same axle? It does, BTW.
.............

According to Ford web site:

.............................................................F250....F350 SRW
Axle Shaft — Spline Minor Dia. (in.).....1.36.......1.50
...........— Spline Major Dia. (in.)............1.50.......1.57
...........— No. of Splines (Hub End)..........35.......37

So the axles are not the same.

[jeb5]

I have the 3.55 and have never looked back. The ratio is not a problem. Your tire capacity is the big issue. This can be solved by getting accurate weights on the rear axle. I am close to my limits, but I am NOT OVER on any of the numbers. 12 MPG consistently. I can pull my trailer and stop my trailer anywhere!!! NO QUESTIONS ASKED. Best power that I have ever owned.

[AH64ID]

jpjulian wrote:
I was a weight cop for the state police for a long time so am very conscious of the various weight issues.

As a weight cop what could you ticket for?

Everything I have read and heard from local cops is registered weight and tires.

With the proper tires a F-350 will have a 7180lb RAWR, for the same axle/tire rating as your F-250.

[Winged_One]

jpjulian wrote:
OOps...forgot. As the original question asked. Those of you who have 2013-14 F-350s, what is your rear axle weight rating?

Joe

If you opt for a DRW, my GAW-R is 9650 and my CCC is 6151.

[jpjulian]

OOps...forgot. As the original question asked. Those of you who have 2013-14 F-350s, what is your rear axle weight rating?

Joe

[jpjulian]

spud1957 wrote:

bpounds wrote:
You would be trading up to an F350 and getting the exact same Ford Sterling 10.5" rear axle.

Just keep your truck and check your wheels/tires. Upgrade those if needed.

X2!!!

OP, you haven't said what your current tires are. If they are 18s then you are good to go.

We have E rated tires @ 3640# per tire so we are well within tire ratings for the load carried. I was a weight cop for the state police for a long time so am very conscious of the various weight issues. The calculated weight of the new Excel is 12,900# as loaded, no water in the fresh or holding tanks. So I know I'll be even more OW when fresh water is added. I know a dually is what is preferred for our application, but none are available so I am considering an SRW but the 3.55 bothers me. One dealer wants to order a 2015 but I know I can get a better deal off the lot rather than order. One of the selling points of this RV was the 7K axles. Right now weight on those axles, again without water, is only 10,400 lbs. so that is comfortable.

Thanks for the replies.

Joe

[spud1957]

bpounds wrote:
You would be trading up to an F350 and getting the exact same Ford Sterling 10.5" rear axle.

Just keep your truck and check your wheels/tires. Upgrade those if needed.

X2!!!

OP, you haven't said what your current tires are. If they are 18s then you are good to go.

[bpounds]

You would be trading up to an F350 and getting the exact same Ford Sterling 10.5" rear axle.

Just keep your truck and check your wheels/tires. Upgrade those if needed.

[AH64ID]

rhagfo wrote:


this may be a bit of the pot to the kettle, as I tow over GVWR, but I do respect axle ratings. I will agree that most 250/2500 have axle rating based on tires, but a 17,500# 5er on 250/2500 running gear is looking for trouble.

What if the 250/350 uses the same axle? It does, BTW.

Dodge does the same thing on the 2500/3500 same axle, different RAWR's. Dodge even used the same axle on a DRW for a 3rd RAWR on the same axle.

Not starting a war, just pointing out 250/2500 running gear is often identical to 350/3500 SRW running gear.

Winged One wrote:
Yes, I do. Sorry, unfortunately, I can't tell you. Don't remember. Haven't driven the truck since October/November and won't for another few weeks.

Based on the math and OEM LT 245/75R17 tires it should be 2065 rpms at 75 in 6th with a locked tq converter. 5th would be 2650 rpms.

[Winged_One]

Atom Ant wrote:

Winged One wrote:

ah64id wrote:

As you can see the trans ratio is very important, and probably why Ford doesn't offer a 3.73 or 4.10 in the 250/350 pickups anymore. They have chosen to do most of their gearing reduction in the trans.

Except that they do. 3.73 and 4.30 in the DRW. Or did you mean just in the SRW? Though you can get a gasser with those gears in a SRW.

Do you have the 3.73? If so what RPM are you turning at 75 mph?

If I'm supposed to have 18% taller gears than you in final drive, it sure doesn't show up on the mpg. You 6.7 guys are doing far better.

Yes, I do. Sorry, unfortunately, I can't tell you. Don't remember. Haven't driven the truck since October/November and won't for another few weeks.

[rhagfo]

KD4UPL wrote:
The RAWR of your current truck is likely based on the tires if it's only 6,100 pounds. Upgrading to higher rated tires (and wheels if necessary) should make the existing truck capable of your trailer.

this may be a bit of the pot to the kettle, as I tow over GVWR, but I do respect axle ratings. I will agree that most 250/2500 have axle rating based on tires, but a 17,500# 5er on 250/2500 running gear is looking for trouble.

[AH64ID]

Winged One wrote:

ah64id wrote:

As you can see the trans ratio is very important, and probably why Ford doesn't offer a 3.73 or 4.10 in the 250/350 pickups anymore. They have chosen to do most of their gearing reduction in the trans.

Except that they do. 3.73 and 4.30 in the DRW. Or did you mean just in the SRW? Though you can get a gasser with those gears in a SRW.

Yes SRW.

[Atom_Ant]

Winged One wrote:

ah64id wrote:

As you can see the trans ratio is very important, and probably why Ford doesn't offer a 3.73 or 4.10 in the 250/350 pickups anymore. They have chosen to do most of their gearing reduction in the trans.

Except that they do. 3.73 and 4.30 in the DRW. Or did you mean just in the SRW? Though you can get a gasser with those gears in a SRW.

Do you have the 3.73? If so what RPM are you turning at 75 mph?

If I'm supposed to have 18% taller gears than you in final drive, it sure doesn't show up on the mpg. You 6.7 guys are doing far better.

[Winged_One]

ah64id wrote:

As you can see the trans ratio is very important, and probably why Ford doesn't offer a 3.73 or 4.10 in the 250/350 pickups anymore. They have chosen to do most of their gearing reduction in the trans.

Except that they do. 3.73 and 4.30 in the DRW. Or did you mean just in the SRW? Though you can get a gasser with those gears in a SRW.

[AH64ID]

For a more apple-apple comparison I looked at the 6.4L Auto ratio's with 3.73 and 4.10 compared to the 6.7L Auto ratio's with 3.55.

The 6.7L is a 6 speed, but has 2 OD's so there are 3 gears before "direct", as mentioned the auto used behind the 6.7 doesn't have a direct but a 1.15:1.

For a 2008 with 3.73's
1st is lower in the 6.7 by 21%
2nd is lower in the 6.7 by 0.4%
3rd is taller in the 6.7 by 6%
4th is lower in the 6.7 by 9.5%
5th is lower in the 6.7 by 15%
Comparing 6th (6.7) to 5th (6.4) the 6.4 is only 10% taller than the 2nd OD.

For a 2008 with 4.10's
1st is lower in the 6.7 by 10%
2nd is taller in the 6.7 by 9%
3rd is taller in the 6.7 by 14.5%
4th is taller in the 6.7 by 0.5%
5th is lower in the 6.7 by 5%
Comparing 6th (6.7) to 5th (6.4) the 6.4 is 18% taller than the 2nd OD.

As you can see the trans ratio is very important, and probably why Ford doesn't offer a 3.73 or 4.10 in the 250/350 pickups anymore. They have chosen to do most of their gearing reduction in the trans.