Donaldson M090544 Muffler ordered - how to install???

[DHerzog]

I went to the local Freightliner dealer today and ordered the Donaldson 51" muffler... cost $80, and should be here Thursday. They had a 51" muffler on display (10+" in diameter with 5" in/out)... that sure seems BIG!!



Now I am wondering how to install it... I measured 51" under my 2004. 5 from the CAT and it looks like the muffler will take up all the space between the cat and the rear axle!!



The stock muffler is offset and the Donaldson is center in and out... . am I going to need a 4" diameter elbow or can it be installed on an upward angle (I prefer not to) or ??????



What have other TDR members done?? Thanks in advance for any input... . Oo.

 

[RTillery]

pick up a 3. 5" to 4" adapter when you get the muffler. I took it down to an exhaust shop and they charged me about $60 I think to put it in. They set it back as far as possible to pick up the 4" tail pipe and welded hangers to grab the stock locations. The adapter went in the front to pickup the smaller section. No Drone, sounds perfect. Worked great. I have been off roading a few times with no problems. I have about 65,000 miles on it now and I would not do anything different. Good luck.

 

[Matt400]

On my 03 I used that muff with the OEM tail pipe. I also used a 4" Banks down pipe that put it straight on to the inlet.

 

[bombero]

If I was you I would take it back an get your money back. I research for months and got a Diesel Performance stainless muff with the off set tube. I am very happy with the sound. It is only about 20in long but its perfect. Anyway, to get your exhaust system apart is a chore. Mine had about 10k on it with no rust. We heated it up with a rose bud torch to cherry red and had to pull it straigh back. It has some tits that prevents you from turning it. Good luck

 

[DHerzog]

Thanks for the responses... .



Since mine has the catalytic converter, the pipe coming off of it is already 4", so I don't need an adapter up front. My bigger concern is that the tailpipe is several inches higher than the pipe coming from the cat. If the muffler was just welded into the replace the original muffler, it would be sloped up toward the back... . I really don't want it to look "junked up", but rather like it was a factory fit... maybe I am too picky... Oo.

 

[JohnnyH]

Look in my picture gallery. I think I have some pics in there of my donaldson install. I had a muffler shop do it. Unless you can find a local shop to bend 4 inch pipe you need to order an offset piece online. Let me know if you have any questions.

 

[DHerzog]

Thanks Johnny H

Thanks for the photos... things sure do look cramped in there. I did not realize there are hangers welded to the original muffler... .



How does it sound on your truck with the cat in place... most threads I have read indicate the owners took of the cat or replaced it with another muffler...



I don't want a lot of noise and sure don't want a lot of drone... thanks for your reply

 

[JohnnyH]

The exhaust shop fabbed up new hangers and welded them to the Donaldson, reusing all of the stock hanger locations. I just noticed you have a Short bed. You may not be able to fit that muffler on your truck. I met a local TDR member and he has a Reg Cab with 8' bed. It looked like it wouldnt work on his truck. As far as the sound, I like it. No drone at all, slightly deeper tone but not much louder than stock.



John

 

[DHerzog]

Thanks again for the response, John



Ya know, I fell a little dumb... I never thought about the muffler being too long for the truck... . ouch!!



When I first looked under the truck, I measured 51" and thought it would be pretty tight... . with an off set pipe and a 90 degree bend in the rear there may NOT be enough room... darn!!!

 

[Buffalo]

I put a 14" Magnaflow right after the downpipe with a piece of 4" pipe which was then welded to the stock 4" tail pipe. The installer just put the pipe up on a slight angle and welded it in place. Looks fine and works great. I wouldn't worry about it. The installer said they do it all the time with no problems.



Joe F. (Buffalo)

 

[JohnnyH]

Dherzog... . All is not lost. Donaldson makes shorter mufflers. I'm not sure how much louder the 41" is compared to the 51, but it may be worth a try. There are other options as well. Do a search for muffler and you should come up with a solution. Remember, keeping the cat is going to give you some sound reduction. Your truck with a cat and 41" muffler may have a similar sound to a truck without a cat and 51".

 

[DHerzog]

Hi John



I have been searching and asking and comparing for over a month and that's how I settled on the Donaldson 51"... seemed to be the best for what I want - lower egt and not loud.



I had a loud magnaflow on a hemi and all my wife did was complain, and even refused to ride in it once... . I jut don't need the hassle.



Oh well, back to the drawing board... . thanks again :{