Replacing Muffler On 275 Cummins

[kennickle]

I'm replacing the muffler on my 98 Gulf Stream. It has a 275 Cummins. The problem: the original has three inch inlet four inch outlet. I can only find mufflers with three inch inlet and three inch outlet or four and four do not have a lot of room to reduce at inlet. So was wondering if three out would be problem or would it cause too much back pressure or is the four out just for looks?

[desertdeals69]

I installed a Aero stainless steel straight thru muffler with 4 inch in and out. Used a 4 to 3 reducer on the inlet. The Aero is shorter so there is plenty of room for it.

[dickandlois]

Ken, The part number on the one used on my freightliner is 20507A-20. Its about 36 to 37in. long with 4in in and out pipe dimensions. The input is slotted so the input can be collapsed down on to a pipe elbow and the output is 4in. and the pipe extension slides over the muffler connection.

There is a transition from the 3in. to 4in. at a section of exhaust pipe near the Turbo. The space between them is connected by a length of flexible 4in. exhaust pipe.

Rich.

[hermanmullins]

Hmmm? I wonder if you can buy a 3" inlet by 4" outlet 11" steel packed Smitty Muffler?

Man what a sound.

Herman

[kennickle]

Thanks for the info the big trouble with mine is that it has a side inlet and not much room to reduce four down to three.

[dickandlois]

Ken, is there room for a elbow at the side input / end of a muffler. Then one could transition down to the 3in. size ? Then use some 3in. flex exhaust pipe ?

Rich

[dickandlois]

Herman, that might work for the open range county,but some live where the locals like life in the quiet lane !!

Some of the boys have street dragsters that are far from quiet. 900 to 1000 HP gas engines have a sound of there own.

Rich.

[kennickle]

Thanks for all the help , went to ABC muffler here in the great north (Edmonton,AB) got them to make one the same as the old one (life time warranty)

nice job.