New muffler problems

FireEater · Oct 29, 2015

Ok, after I changed the cam I finally had time to change the loud muffler.

For those not familiar with my motor, I run a built 5.9 with PPH headers, high flow Pypes cat and 3" exhaust all the way out.

I changed from a Magnaflow muffler to a Flowmaster 50 SUV muffler.

Now it seems that this muffler might be to restrictive as I have major back pressure. The whole Durango vibrates really bad on take off. Settles down some until around 55 to 65, when it gets bad again. Then is pretty good at 70 to 75.

I'm wondering now if I need to go to a Flowmaster 40 series? I'm trying to keep it as quiet as possible. The Magnaflow was simply to loud, so that is why I went to the Flowmaster 50.

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FireEater · Oct 29, 2015

It is actually the Super 50 Series, 853057

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FireEater · Oct 29, 2015

Yea, I watched that video a dozen times before I chose this muffler.

I just got off the phone with Flowmaster. This problem baffled them. They suggested that I bang on the muffler with a rubber mallet to see if anything inside broke loose, maybe impeding the flow.

He said that it is the perfect muffler for my application though. I banged on it and nothing seems loose. So I banged on the cat and heard nothing.

I'm dropping the exhaust out later today to take a closer look at the cat. It's a Pypes stainless high flow cat and it's been on there a year now. Maybe the honeycomb inside it is clogging.

I also blocked the tail pipe with my hand real easy. It really has hardly any pressure on it, which leads me to believe there is clogging somewhere along the line. Also, this problem didn't start until a few weeks after I installed the muffler. It has gotten progressively worse over time.

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dizzyD · Oct 29, 2015

if you have a hand held IR thermo gun, you can track down the blockage point by scanning back to front and find where its temp changes more than 10 degrees.
My 93 Dakota 5.2 did funny marble bouncing notes when I went too large on muffler, actually it was backfires under load, I had to reduce the 3" pipe down to 2.75 from muffler to end tip.

FireEater · Oct 29, 2015

I actually have one here at my second job. Thanks, I'll use it when I return to the office.

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FireEater · Oct 29, 2015

Well now I'm baffled. Unless the new Flowmaster muffler some how clogged up, I have no idea what is going on. I just removed the exhaust, my cat is a hollow shell. If I remember correctly, it has always been that way.

When I rev it up in the driveway to 3000 to 3500 steady, it sounds great. No vibration or rattling. But when I take off from a stop, it vibrates pretty bad, shaking the steering wheel. Then around 55 to 65 it is a steady hard vibration, ratting everything inside pretty good. Then I let off the gas, RPM's drop and it all stops, until I hit the gas again, then back to vibrating.

I've even put it in neutral at 60 and as soon as the RPMs drop, it gets quiet. Then I'll rev it up while still in neutral doing 60 and it starts vibrating real bad again. But I cannot get it to mimic that sitting still in the driveway reving it up as I said before.

MWeed · Oct 30, 2015

Is it possible that you have broken a belt in your tire or blistered a tire?

FireEater · Oct 30, 2015

Not the way it's acting. If it was that, it would be continuous. Once I let up off the gas and the RPMs drop to a 1000, it all goes away, even though I'm still traveling at 65 MPH.

Then to double check it, I get up to 65MPH, put it in neutral, and when the RPMs drop, it goes away again. So then while still coasting at 65MPH in neutral, I rev it up and it all comes back momentarily until the RPMs drop again.

So basically, it's is vibrating real bad at speed, until I let off the gas, while still at speed.

I'll shoot some video in the morning on the way to my second job. It should pick it up easily.

I can also mount my GoPro underneath and shoot footage of the muffler.

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FireEater · Oct 30, 2015

Found the problem! This morning when I left for my second job, I romped on it and BOOM. Driveshaft falls out.

Rear u-joint snapped. They were the original ones and had no grease fittings. So I pulled the shaft from the transfer case, locked it in 4-high and headed to O'Rielly's. Picked up two new u-joints and came in to work. I'll changed them out in the shop here.

The old ones were dry and burned up, just waiting to fail. I was even under it a few days ago, shaking everything and hitting things with a rubber mallet.

Then with the vibration happen while coasting at 65 in neutral ONLY when I revved it led me away from everything except the exhaust. Coasting at 65 in neutral and at idle and no vibration.....wierd.

The new u-joints have zerc fittings to grease them.

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New muffler problems

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MWeed

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