I just picked up my Nelson 51" (PN# 86131M) and I was wondering if there is an inlet? There is no writing on it but one side has a flat surface when looking at the end and the other side is sorta indented. Has anyone put this unit on there truck and does it matter what way it goes on? Thanks

 

Mine had an arrow imprinted in the side which stated which end was the inlet. I got the 090544.

 

You can tell by the shap of the muffler one side is rounded outward the other is inward inward goes to the back.

 

The flat side is the outlet and the indented side is the inlet, they are intended for vertical mounting on a semi and this is for rain run off

 

This is installed correctly. Hope this helps

 

Hmmm, goona hafta crawl under to see if my 40" was installer right.
Guess it makes no difference though, sure sounds good...

 

Smokema If thats the case what keeps water from being traped on top! Diesel shop told me the rounded end went up for that reason.

 

Doesn't the 51" have a big hollow section just inside one end? Isn't the hollow end sposed to be the 'out' end?

 

What are you looking at? The round end does go up when the muffler is installed vertically. Horizontally the round end goes to the rear of the truck.