Installed Donaldson today. Parts:
Donaldson M085171 $64.05
2 Clamps (band type) 733-3224 from Napa $8.45 ea. ($16.90 total).
1 Muffler Clamp HPC350 from Napa $2.91.
1 Reducer 41991 $13.49 from Napa.
Total with Taxes $99.60

Cut pipe just in front of front muffler clamp (kept exhaust pipe hanger that is welded to pipe just in front of muffler inlet pipe. Butted new Reducer up to it and used the muffler clamp. Used band clamp to clamp reducer to new muffler. Note Muffler1 picture shows - heated and bent old muffler hanger out of the way; it was too close and might make contact.

Cut off pipe about 2" downstream of old muffler outlet pipe, about 1" after it expands to 4". Slipped stock exhaust pipe into rear of muffler (tight fit).

Sounds great. No drone. Glad I did not go with longer Donaldson.

Trying to post pictures, don't know if it will work.

Have sound files before and after but no where to post them.

 

""Cut off pipe about 2" downstream of old muffler outlet pipe, about 1" after it expands to 4". Slipped stock exhaust pipe into rear of muffler (tightfit).""

So I thought the inlet pipe was 3.5" od and the outlet was 4" od?

It sounds like the outlet is smaller then 4 then goes out to 4" after the clamp to the muffler??

I was going to do a straight pipe for now then do something like that if it is to loud.
What I wanted to do was
3.5 to 4 reducer then SS flex pipe 4" off a big truck. >>>
stock pipe 3.5 od to 3.5 id up(reducer) to 4" od 3' +/- ss 4" id flex with a clamp over the 4" od tail pipe.
Is this not do able is the stock outlet smaller then 4" od?
Jon

 

The stock muffler on my 2003 HO is 3.5 OD inlet and 3.5 OD outlet. About 1" downstream of the stock muffler's outlet pipe, the tailpipe expands to 4" OD. That's where I cut it off so that I could use the band clamp connect the 4" muffler to the 4" (cutoff) tailpipe. The 4" tailpipe actually fits inside the ID of the new muffler and works nicely with the band clamp. Since the stock muffler inlet is offset from the outlet, you have to do a little tweaking to get the alignment acceptable.

I used the band clamps in order to be able to 1) either put the stock muffler back on, or 2) put on a different muffler. I think I'll keep it just the way it is. I may add an additional muffler support since the old muffler had 3 hangers to help manage the weight. I think I'll use 2 of those mountings and fabricate some 1/2" rod to help with the weight, even though I have not seen a problem.

Note: pictures in my Member's Photo Gallery exit.

 

I am thinking of doing this exact mod. Would you say the sound is a lot louder? What about turbo whistle? If I send you my email could you send me the before and after wav files? Thanks, Wade

 

WJB, I'll send you the sound files separately.
As far as the sound, if you are standing back at the exhaust or standing by the road while the truck is going by, it sounds quite a bit louder - and very nice. Sounds are a matter of opinion, I guess, and this is just about perfect for me. Even if it was a little louder, it would not bother me. I end up rolling down the windows on the passenger side a lot to hear it better.

When you stomp on it, you can definitely hear the tone better, but inside the cab, it is still not too loud. Going down the highway at 60mph, I can hear it a little more with the windows up. If you take it up to 2500 rpm, you can hear it more even with the windows up, but not too obnoxious.

My son says the turbo whistle is more pronounced, but I guess I am loosing that sound range, because I never heard it much before and only a little now.

Since I have fiberglass running boards, I had to twist the tailpipe downward a bit to keep exhaust away from the running boards. I noticed then that it was backed up a little under the truck, so I plan on getting a chrome tip to bring it back out.

I have a 30ft 5ver that I will be towing, so I did not want it so lound that I could not stand it. I think I'll be fine, but it will be a month and a half before I know for sure.

 

That looks like a great price on the Donaldson muffler. Where did you get it?

 

I got the muffler at the local Peterbuilt service center in Findlay, Oh.

 

Looking at the instal pics...I have a question. Did you mount your muff the correct flow direction? I was told that the arrow was the flow direction, NOT pointing to the inlet. Mine is mounted the other way. Does anyone know more about this issue including any pros/cons in the direction. I welded my hangers...I really hope that mine is pointed the correct direction.

 

Even though it says INLET right on it?

 

Yep...that is what the Donalson Dealer (Stewart & Stevenson) said in Denver. That would put the expansion chamber closer to the front of the muffler. I like the way it sounds and it seems to help EGT temps 150* or so. The biggest difference is how rapid they raise. I can actually take my eye of the gauge for a few moments now. Anyone else out there know the answer?

 

Hee heee (sorry). Nope, expansion chamber goes to the rear of the truck. Arrow points to the inlet, not an indication of flow direction. Don't worry, it changes nothing but the sound. I had actually thought about turning mine around to see if I like the sound better. That "expansion chamber" is what gives it its deep rumble. At times, I wish mine wasn't quit so deep. I think it cancels out some turbo whistle. At low RPMs, I get plenty of whistle. At heavy throttle when your really pushing some air through it is when the expansion chamber is doing its job, toning everything down. You may be on to something so let us know how you like it.

 

I have lots of whistle...it only gets real deep when it is WOT. Why the hell did the dealer tell me that. I asked him three times. He kept saying that is the flow direction. Everyone says my truck sounds like a semi. It is real quite inside tell you are on it. I can't hear it at all cruizen...even 90 on the highway or up a pass. Idle, it sounds a little deeper that stock with a slight whistle. Slight throttle is just whistle. If you muff comes off easy than mine (since I welded back the OEM hangers on to the muffler), please swap it around some day and compare.

I hope it really has no performance penalty...or maybe a gain!
Maybe a little luck from my stupidity. **** dealer.

 

Have you guys seen any gas mileage improvements with your muffler mods.

Pulling a small 16 ft. enclosed cargo trailer I am only getting 11 mpg.

Any suggestions.

 

More miles on your truck and/or slower speeds. Enclose cargo trailer are like parachutes. The aerodynamics kills mileage more than weight.

 

can u send me the sound files?

Dan

df5152@portjeff.net