Expedition vs. Durango?

Just a couple of designer/engineering points....

all things designed & engineered are NOT for the good days when a riding lawn mower
'can do it', but for the warranty period (plus some margin) and worst day out there

The issue(s) will not manifest itself/themselves instantly...it will take some
time.

Maybe to folks who buy and trade ever few years will not ever experience ratings
failure...unless the over loading is extreme...

Monocoque/uni-body can be designed to be tolerant of WD forces on the belly pan
but that would mean increasing the box section and gauge

Grit dog wrote:
The previous gen Durangos with the 5.7 are great tow vehicles. They have the same drivetrain as the 1500 Ram.
Old boss had a 08? Durango and an Avalanche and he said the Durango whipped the Avy both in power and stability pulling his wakeboard boat. 5-6klb load.

I would not consider the Ram 1500's ancient 545RFE a great drive train. It's both weak and poorly spaced in terms of ratios.

The new Durango's W5A580 and especially the post-2014 ZF 8 speed is vastly superior in terms of both strength and ratios.

There's a reason Ram has also gone with the ZF.

mileshuff wrote:
For me the question isn't whether something will break or not. I agree, engineers will take care of that. My issue is in handling of the load. How much body and frame flexing? I prefer live axles and a stiff frame over independent suspension and unibody. In vehicles I've towed with I see a big difference in how they handle the load.

Valid concerns once again; let's dig up some engineering data on torsional rigidity (all units N-m/deg):

http://youwheel.com/2014/04/25/car-body-torsional-rigidity-a-comprehensive-list/

Chrysler Durango (not the latest generation) 6,800
Jeep Grand Cherokee (WK2, 2010-) 23,000

Since the modern Durango is built on the Grand Cherokee / ML platform, we can assume it's closer to 23,000 than 6,800 (which may be a gen 1 Durango).

Contrary to popular belief, unibody chassis can be, and are, typically stiffer than body on frame. And it's not hard to see why. Go twist an aluminum ladder, and then try twisting an aluminum tool box, see which is harder to twist and bend!

On that page, you'll see some of the highest values are generated by unibody monocoques:

SUVs - GMC Acadia, VW Touareg, BMW X5, etc.
Cars - BMW 5/7 series, Mercedes S-Class, VW Phaeton, etc.

The previous gen Durangos with the 5.7 are great tow vehicles. They have the same drivetrain as the 1500 Ram.
Old boss had a 08? Durango and an Avalanche and he said the Durango whipped the Avy both in power and stability pulling his wakeboard boat. 5-6klb load.

Dottie5 wrote:
We tow a Keystone Passport with a 2014 Durango V8 Hemi. We have a weight distribution hitch and antisway bar. We've taken it over the mountains from Denver area to Moad, over Raton Pass and to Iowa. So far so good. It tows fine. Only the three trips since we just got it in March but are planning another up to the mountains over Labor Day.

And I tow a Keystone Passport 2810bhwe with my '14 Durango Hemi. Works great..only "problem" I had was getting enough tongue weight on the trailer..just had to rearrange some of the heavier stuff inside.

RoyJ wrote:
While concerns regarding concentrated loads on a unibody is valid, I think this is one area where we should put out faith in OEM engineers. I doubt they'd release a hitch rating without considering all static and dynamic forces acting on the hitch.

For me the question isn't whether something will break or not. I agree, engineers will take care of that. My issue is in handling of the load. How much body and frame flexing? I prefer live axles and a stiff frame over independent suspension and unibody. In vehicles I've towed with I see a big difference in how they handle the load.

Dottie5 wrote:
We tow a Keystone Passport with a 2014 Durango V8 Hemi. We have a weight distribution hitch and antisway bar. We've taken it over the mountains from Denver area to Moad, over Raton Pass and to Iowa. So far so good. It tows fine. Only the three trips since we just got it in March but are planning another up to the mountains over Labor Day.

Which model Passport do you have?

mileshuff wrote:

Thsldo wrote:
The new durango is actually longer and wider then the previous gen.

Just looked up specs on both my 2004 and the newer 2014 Durango's. The 2004 is slightly wider, taller, longer and more ground clearance. I'm also seeing quite a bit more interior space, legroom, head room, etc. in the older version. I'm using Edmunds online specs for both. Parked next to a newer D and the older looks quite a bit bigger but could be an optical illusion since the new D's are more rounded and streamlined contours.

I apologize, for some reason I thought for sure the new one was longer and wider, it's just the wheel base that is longer, and only by 1/2 an inch. Sorry for providing wrong info!

While concerns regarding concentrated loads on a unibody is valid, I think this is one area where we should put out faith in OEM engineers. I doubt they'd release a hitch rating without considering all static and dynamic forces acting on the hitch.

We can do some very simple calculations. Assuming worst case of 1000 lbs hitch weight with no equalizing hitch. Then assume a drawbar length of 1 foot, and a hitch mounting hole spacing of 1 foot (2 bolts per side on the Durango).

Simple free body diagram would tell you the rear bolts have a net force of 2000 lbs down, and the front bolts 1000 lbs up.

2000 lbs split into 2 bolts means 1000 lbs per bolt. A typical automotive frame/subframe should be at least 40ksi in yield strength. Meaning each frame rail only needs to be 0.025 square inches in total cross sectional area to support the weight.

I can guarantee the most flimsy frame in the world should be 10 times that amount!

Thsldo wrote:
The new durango is actually longer and wider then the previous gen.

Just looked up specs on both my 2004 and the newer 2014 Durango's. The 2004 is slightly wider, taller, longer and more ground clearance. I'm also seeing quite a bit more interior space, legroom, head room, etc. in the older version. I'm using Edmunds online specs for both. Parked next to a newer D and the older looks quite a bit bigger but could be an optical illusion since the new D's are more rounded and streamlined contours.