For a while I have been towing a 6x8 enclosed cargo trailer with my 99 Durango with the 5.9 and full time 4 wheel(153,000 on it). Last month I upgraded to a 16x7 enclosed cargo trailer(carrying about 5k lbs), and since then the problems have began. A few months ago I noticed a squeeling from under the center of the vehicle, but never got it checked out(it was there whenever the engine was running).

After taking the 16x7 on it's first road trip, we blew the connection between the header on the passenger side, and the Y pipe. This, in turn, melted the air intake hose, and the front passenger brake line(while on the highway). We had to have the Durango towed back home, and it ended up having the Y-Pipe, cat, muffler(replaced with super 44), and tailpipe replaced, along with getting some Billstein HD shocks all around(the intake was replaced from junkyard parts).

I'd assume the squeeling previously stated was caused by a clogged cat considering it went away after the exhaust work was done.

Just last week, we had a leak in the brake line that runs along most of the vehicle, on the driver side frame rail, next to the gas tank.

Since all this has happened, I have noticed the truck has an extremely hard time passing 55 MPH with the 7x16 behind it.(right before the y pipe blew, it was getting up to 75 without trouble).

I am planning on investing in a WD hitch to level out the truck, and a scanguage to see if there is anything else odd that's not showing up on the Instrument cluster.

Is there anything else that I am missing that might be the problem?(possibly related to the heat on the passenger side of the engine compartment)

Any other suggestions for things I should have worked on to better accommodate the towing?

 

Well did ur truck come with the tow package? does it have the extra transmission cooler mounted in front of the radiator? very important o have this when pulling with these, transmission run hot. That takes me to changing the transmission fluid regularly an do it before then general maintenance mileage. another words change it about 3-4K before its do. This one i am not positive on but u changing the cat an new pipe would change flow in engine as well. The computer will take time to adjust to the knew flow an make the proper adjustments over time to make the best "hp", how long or how many miles this usually takes? someone else may be able to point u closer then i could at this time.
u had the injectors cleaned recent or at all?

 

It did come with the towing package, so I'd assume it to include the trans cooler. I am not sure when the trans fluid was changed last, but I'll look into it. And the injectors have not been cleaned as far as I know.

 

the official call on the computer relearn time is 300-500 miles, it usually takes much less than that tho

 

I bought a ScanGauge for my Excursion just so I would have tranny temp. I hooked it up in the Durango and it does NOT show tranny temp nor can it be programmed to do so. Just a heads up.

Oh, what gears do you have? I switched from the stock 3.55:1 to 4.56:1 and that made a night and day difference when towing.

 

It's running stock gears, but since it's the 4wd model, it will be costly to swap em.

 

stock gears doesnt answer it, could still be either one of two (3.55 or 3.92)

 

My mistake, but I will obtain the info on it's current gearing tomorrow.

 

Check in the glove box. The data sheet will tell you what gear it is.. assuming that it's never been changed.

 

the lag your getting after 55 is probably because you changed the size (back pressure) of your exhaust system. The more back pressure you got the better torque you have and the easier it is for the D to pull anything.. You have a few options if you wanna get back some of the torque. A good tune up is always very good.. I pull a 4000 lb boat around every weekend or so and I found that my least favorite upgrade did the most while pulling the boat at highway speeds.. That upgrade was putting on a taller intake manifold which moved that durango's power curve from stock 0-2000 rpm to 1500-3500 rpm.. those are manufactures stats so a good chance that they're bull but the best upgrades for any power and torque on the D is easing up the intake system..

I call the intake my least favorite because it was expensive as all heck and actually hurt city driving mpgs. but i got more power!