My TT Towing Capabilities?
09-24-2015, 06:13 PM
#21
I am confident in what the guys say from UNOH, but that was on an earlier 9.75, clearly with Ford rating the 2015 6 lugs at 4800, there is no doubt the axle itself will handle the weight, the limiter is wheels, springs and tires.
09-24-2015, 10:27 PM
#22
They are underrated for sure, in one way, but calculatedly so, because of fatigue cycles and usage cycles. I design weapons components, and we do the same thing in my line of work. You purposely over build so that the fatigue life of the part is as close to infinite you can make it.
In the case of the trucks, both frames would be almost equally rigid. On shorter sections (short wheelbase) builders spec for strength on longer wheel base it's more for deflection hence slight thickness increase.
RBM (resistance bending moment) is calculated by multiplying sectional modulus by yield strength. This is the true rigidity measure of a frame. For the 09 to 14 trucks the supercab 4x4 145wb trucks have a RBM of 281,010
The HD trucks have an RBM of 259,200. Both of those measurents are in inch pounds. Both are very rigid, but it is interesting that the supercab or shorter WB trucks rate higher. All this makes me feel even better about my supercab and towing my gooseneck.
Even more interestingly I used the source book for the 13 SD and calcated the RBM of the SD frames and it certainly shocked me that it was lower than either of the 150 frames it also has fewer cross members. It's RBM is 241200. They have either 5 or 6 cross members vs 7 on the 09-14 150s.
In the case of the trucks, both frames would be almost equally rigid. On shorter sections (short wheelbase) builders spec for strength on longer wheel base it's more for deflection hence slight thickness increase.
RBM (resistance bending moment) is calculated by multiplying sectional modulus by yield strength. This is the true rigidity measure of a frame. For the 09 to 14 trucks the supercab 4x4 145wb trucks have a RBM of 281,010
The HD trucks have an RBM of 259,200. Both of those measurents are in inch pounds. Both are very rigid, but it is interesting that the supercab or shorter WB trucks rate higher. All this makes me feel even better about my supercab and towing my gooseneck.
Even more interestingly I used the source book for the 13 SD and calcated the RBM of the SD frames and it certainly shocked me that it was lower than either of the 150 frames it also has fewer cross members. It's RBM is 241200. They have either 5 or 6 cross members vs 7 on the 09-14 150s.
09-25-2015, 04:05 AM
#23
No problem, glad to do it. I spend a lot of time with metallurgy in my work, so stuff like this and how axles are built and rated intrigues me. That is why once I worked out the 150 frame stuff, I had to check the SD ones. I just wanted to compare the two using Ford's supplied data.
The guys in the article from UNOH really dug in deep on the 9.75 from the 97-03 trucks. The materials used in the ford 9.75 are high end stuff, it's a really well engineered part, and just as good or better than the Dana unit.
I think from what I am reading that the 2017 SD trucks may end up on a beefed up version of the current 150 frame, which after this little digging in I did, would not surprise me. They have already stated it's going to use same cab, cabin, doors and such, so that would dictate same frame width in the cab area for sure. Extend the front if need be for diesel and V10 length, they have said 6.2, 6.8, and diesel for sure offered. I think bigger axles, tranny, driveshafts, transfer cases, and suspension for sure, pretty much same frame would not surprise me much at all.
The guys in the article from UNOH really dug in deep on the 9.75 from the 97-03 trucks. The materials used in the ford 9.75 are high end stuff, it's a really well engineered part, and just as good or better than the Dana unit.
I think from what I am reading that the 2017 SD trucks may end up on a beefed up version of the current 150 frame, which after this little digging in I did, would not surprise me. They have already stated it's going to use same cab, cabin, doors and such, so that would dictate same frame width in the cab area for sure. Extend the front if need be for diesel and V10 length, they have said 6.2, 6.8, and diesel for sure offered. I think bigger axles, tranny, driveshafts, transfer cases, and suspension for sure, pretty much same frame would not surprise me much at all.
Last edited by 5.0GN tow; 09-25-2015 at 05:38 AM.
09-25-2015, 05:51 AM
#24
I Just ran the same numbers on 2015 150 frames. There is some good and some bad news there. The good is all ftames are now from the 49300psi yield strength steel, the bad news is the sectional modulus is down a bit on some frames while up on others. The HD/LD designations are a mystery. I assume and dont know for sure but would guess that those frames vary by GVWR and engine selection etc. LD frames have sectional modulus 4.95, HD gets 5.73, HDPP trucks get 6.28. The HD is about same as 09-14s RBM wise, the HDPP trucks are way up, and the LD is down a bit. Both the HD and HDPP, and even the LD exceed the current SD in RBM measurement, and the 15s added another crossmember. Looking at this, I see them adding rail thickness or height to increase SM and thereby RBM for SD use and then putting HD driveline under it. Doing so saves them tons of money and gets a lighter and stronger truck than current SD.
09-25-2015, 09:05 AM
#25
Senior Member
AFAIK the only 2015 F150 with a 4800# rear GAWR is the HD Payload truck which has a different rear axle than the regular trucks with lower rear GAWR.
09-25-2015, 04:57 PM
#26
Looking that over and comparing to the 09-14 it looks like it might be the raptor axle spec for the 2015 HD but with 3.73 gears. That is the only heavier duty version they make it has 35 splines and slightly larger shafts. Odd they did not use it with HD payload in 09-14 trucks which were themselves heavier. The 09-14s that were rated at 4800 were spring pack and tire related for the most part other than the 7 lug wheels. The axle shaft dimensions and spline counts were the same. Like I said before, with this axle and frame combo, it's usually springs and tires/wheels that will hold you back.
09-26-2015, 11:57 PM
#27
So today I saw a great deal on a Jayco Jayflight SLX 264 BHW. 29' UVW 4550/ Dry Hitch at 490. It allows for 1960 additional to the 4550 but if I never take to that level and only concern myself with the overall hitch weight and my payload does that seem doable? What I guess I'm saying is I don't expect to carry enough to get her to the max allowable GVWR which seems high at almost 2k. Seems if I expect to only carry a thousand pounds on one TT and it keeps me at an acceptable overall weight why can't I expect the same from another comparably weighted trailer that I don't come close to maxing its allowable GVWR. To clarify-Trying to understand and compare a TT with a dry hitch 460/ UVW 4330 /GVWR 5500 @24' total maxed out vs. dry hitch 490/UVW 4550 / GVRW 6400 @29' that is not maxed out but only loaded to the same 5500 as overall. I know the extended length becomes a factor but isn't the end payload result the same?
09-27-2015, 09:24 AM
#28
Senior Member
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To clarify-Trying to understand and compare a TT with a dry hitch 460/ UVW 4330 /GVWR 5500 @24' total maxed out vs. dry hitch 490/UVW 4550 / GVRW 6400 @29' that is not maxed out but only loaded to the same 5500 as overall. I know the extended length becomes a factor but isn't the end payload result the same?
To clarify-Trying to understand and compare a TT with a dry hitch 460/ UVW 4330 /GVWR 5500 @24' total maxed out vs. dry hitch 490/UVW 4550 / GVRW 6400 @29' that is not maxed out but only loaded to the same 5500 as overall. I know the extended length becomes a factor but isn't the end payload result the same?
But estimating TW of a loaded trailer is tough. A lot depends upon where the axles are placed, where the storage compartments/refrig are placed relative to the axles. And if you carry water or waste, where the tanks are located relative to the axles.
Maybe you can estimate what % of that 1000# you add will end up on the tongue? It would be sort of like a teeter-totter; weight placed on the axles will not affect TW, in front of the axles will add to TW, behind the axles will subtract from TW depending upon distance.
Both trailers will have the same weight of propane, batts and hitch on the tongue though. In my case that's ~250#, but I've got 2-30#tanks, 2 batts and a big hitch to handle my ~1200# TW. You might have only 150# there? Add that to the dry TW.
Both my trailers have ended up with high (15%) loaded TW, but were advertised with much lower dry TW. Because my truck has a high payload (4x2, SCab), I'm under the GVWR, but am over the rear GAWR by 1-2%.
I would guess either one of those trailers would be fine with your truck if you were careful about loading. And, after properly setting up your WDH, if you don't care for the handling while towing, stiffening the suspension and adding LT tires helps.
Good luck.