I am buying a Roush body kit and exhaust for my 2008 Mustang GT, but there are two choices for the exhaust: Legal (401338) and Off-Road (401339). The pictures look alike and both are cat-backs only. So, how are they different? What makes the off-road not legal? Has anyone had experiece with the sound difference? Thanks much for the help!

 

If it's a cat-back system only, then likely the one version is louder and therefore not legal in (probably) California and maybe a handfull of other states, but Cali I believe is the only one that is significantly different from the rests in terms of sound limitations. Anyone here from the left coast, jump in here........

Otherwise, you'll be fine anywhere else for the most part.

 

I have the Roush off road exhaust and really like the sound, I actually wish that the car was a bit louder so I will down the road add headers

 

Nobody else knows anything about these?

 

you will be fine as long as your state doesn't have a decibel law. my friend has these mufflers on his roush and they sound great and have a nice deep growl to them.

 

i have a 428R with the "legal" Roush axlebacks and wanted more sound but instead of investing in the "illegal" off road roush i bought and installed a magnaflow catted x-pipe. more growl when you step on the gas pedal and less drone @ cruising/highway speed (75-80 mph). my old ears are happy!!!

 

Roush Off-Roads are FRPP Stingers
Roush Stock (Legal) Mufflers are similar to Quiet Magnaflows

 

Nope ......I don't think so. Not with the rectangular exhaust tips. I think they are Roush and only Roush!

 

428R uses round tips and are Stingers. They don't use the rectangular tips on 428R.

 

Ahh.. maybe I am only half correct. And what is the actual differences between a Roush 427 and 428R anyway. I have seen both at a local dealer and I can't see any difference except in the badging and decals.

 

My cousin explained it to me and I forgot. He has the 428R. Any Roushheads willing to educate us?

 

Ive got the Roush exhaust that looks identical to the Borla and FRPP stingers. This exhaust paired with my Kooks lt headers with hi flow cats sounds very good (to me anyway) but it is on the loud side, but I like that.

 

So you would be a good one to ask about what is the difference between the Roush 427 and 428R other than the mufflers?

 

427R conversions were supposed to be for MY 2007 only. about 1100 or so were made and roush said they sold so well they carried it into MY 2008 for another 1000 or so conversions. 427R's were a little less i HP (410?). roush wanted a more limited edition mustang to continue his tribute to the 400 series motors of the classic mustangs, hence the 428R in MY 2008.
Only 200 428R total conversions. 435hp, polished supercharger (vs black for the 427R), slightly smaller pulley for a little more HP, some billet engine dress up items under the hood. i think 429R's are now available or can be ordered from roush dealerships. btw, the square exhaust tips were used on the Roush Stage 3's, 427/428 use the rebadged Borlas. hope this helps

 

In California, the highest dB level you can be at for exhaust on a passenger car is 95 dB +/- 1 dB. Stock Mustang GT exhaust (1999 to 2004 models) is 92 dB. My Bassani cat back measured 99 dB. Bassani cat back with catted X pipe measured 118 dB. This was done using California's Standard test procedures at a smog ref station. Assuming an '05 and up GT is around the same level as a '99-'04 GT, Ford doesn't give you much room to go any louder legally. I bet the Roush street legal exhaust is not even street legal at all.

And yes it was because of a ticket.

 

they're probably street legal everywhere, except california

 

New York and Hawaii have the same rules I think.

 

Here is link to an article about a few different axleback setups. I do question the article however. According to the article. The JBAs were the loadest among the axlebacks tested. This includes borla stingers. I have JBAs, while the tone is excellent, I wouldn't call them loud.
http://mustanglife.tenmagazines.com/...ticle&aid=3827