I have some concerns for my Durango. It's an '04 5.7L Hemi. I have currently about 147,000 miles on it. It is constantly used to tow with (upwards of 10,000 lbs)

* Sometimes sounds extremely throaty when going up mountains and in extreme heat (western states and its summer). This seems to happen most when towing but does occasionally happen when I'm not.

* After turning the vehicle off, I get a low humming sound from the middle right of the vehicle for about five minutes.

* When in wet weather and idling, it stutters. I have had it die on me in a car wash before.

* When first starting the vehicle for the first time in a day, I get a speedy tick from the right side of the engine compartment. Once it warms up it goes away. I have read the other articles here with this similar problem and they all seem to lead me to the bolts to the exhaust header needing to be replaced. Probably along with the gasket as well. Please correct me if I'm wrong.

Outside those problems, everything else seems to be OK.

Please note that I have replaced the spark plugs with Bosch Platinum +2 and the stock filter with a k&n stock box replacement.

Some things that I am looking at doing are replacing the stock intake with an afe cold air intake stage 2, adding an afe throttle body spacer, and replacing the thermostat with a jet low temp thermostat.

Somewhere down the line, I may replace the stock exhaust piping and possibly add a cat back system as well. Though this really is unlikely as I should have done this long ago as the prices are a little high for the 150,000 miles or so I may have left on it.

Any insight on my problems or maybe things I could do to improve overall performance and fuel economy would be greatly appreciated.

Thanks.

 

The manifold studs are usually at fault on the 4.7L, not so much with the 5.7L. Forget about the throttle body spacer as it is a waste of $100.00, but the cold air intake and cat-back exhaust will help. THe humming sound may be your A/C running to remove condesation, but that is just a wild quess,
FF

 

The louder when hot and the noise after shut off is probably one in the same. Have the cat/muffler checked. Cat will be under federal warranty. May be time to replace one or both. The resonator is in the rear so probably not that.

Skip the throttle spacer, it's junk but makes a nice paper weight.

IndyDurango

 

Thanks for the reply.

If you don't believe the manifold studs are at fault on this engine, any insight on what it may actually be?

I noticed that you have an AEM cold air intake not AFE. Is there a particular reason why you chose the AEM over the others available on the market?

Also, I have thought about a tuner, but am extremely worried that I might screw something up royally. Could you give me some insight on yuour experience with them.

Thanks.

 

Thanks for the reply.

If my cat is going bad, it would explain a little about my fuel mileage. I currently get about 22 mpg hwy not towing and about 16 city not towing. I don't live in a state where I have to pass a smog inspection when I register my vehicle, so I might just cut out the cat or leave it as is. Unless of course there is something that I can harm by not fixing it. As for the muffler I'm certain that it's not that either. Anyways, I'm most likely going to replace the muffler with the cat back anyhow.

Thanks for the insight on the throttle body spacer. I will spend that hundred on the cold air intake.

Any insight on the pinging that I get when its cold?

Thanks.

 

Frog:

What rpm do you hear this "throaty" sound at? The OEM Durango system is known to have a resonance in the 1900-2200 rpm range. I would agree that the Hemi has quite a nice growl when the rpms climb.

The consensus on plugs is usually to go back in with the OEM Champions. Many folks have reported rough running and general disappointment when putting Bosch or other multi prong plugs into the Durango engines.

With almost 150k on the odo and towing as much and as hard as you do, hopefully you have done regular fluid/filter changes to let your tranny live as long as it can in that environment.

If I ran mine that hard, I would be doing it every 40-50k at minimum.

Don

 

I suggest ALWAYS putting the CAT back in place. If it needs replaced, that means replaced. Not eliminated. To much else going on electronically to eliminate it.

InyDurango

 

Don,

Thanks for the reply. The throaty sound that I hear is never really at a particular RPM. It'll come and go. Most the time though it never happens above 3500 rpms. As for the plugs, I have been satisfied with the Bosch Platinums +2. They have improved my overall fuel economy and the only time it ever runs rough is when it is extremely wet out. But this only happens if I'm in stop and go traffic. I have suspicion that one or more of my coils is getting wet and this is the cause. Just haven't gotten around to replacing the wires and coils yet. To much of a chore.

As for the tranny, I do regular maintenance on it like clock work. Every 40-50K like you suggested. I also have now been running Castrol High Mileage 5W-30 since I rolled over to 75K miles. I change it about every 7-10K miles. When it comes time to change (about once a month) always comes out full and not very dark at all. No oil leaks nor ever any oil leaks.

~Fr0gster

 

If I were not to replace the CAT, what potentially could go wrong?

 

It is illegal,
FF