"Noise vibration harshness" (NVH) opinions needed

[BullittAndy]

I need other's opinions about how a Foxbody should "feel" with regards to Noise, Vibration Harshness (NVH). I've got a 91 LX hatch with an AOD that vibrates (slightly), makes slight creaking noises and is mildly harsh but I'm not sure if something is wrong with the car or if it's me. Car has 4.10 gears, rear control arms (poly bushings), 17 inch tires. Here's what I've done to the car, all of which have greatly reduced NVH.
-New wheels and new balanced tires
-balanced driveshaft and phased driveshaft
-new balancer
-new motor and tranny mounts (rubber)
-dynomat and huge amounts of other sound deadener
-new door and hatch seals
-new door strikers
-rear shock tower, front tower and k-member brace
-subframe connectors
I'm comparing this car to a 1997 Infinti Q45 which is tomb quiet comapratively so I'm not sure if I'm being fair to the Mustang, can they be noise and vibration free?

 

[srothfuss]

The Fox Platform was never the greatest feet of chasis engineering to begin with. Stuff a V-8 and a big transmission in there and you are bound to hear every creak, groan and buzz as you drive down the road. It takes some time to get used to, but eventually you will know what the car is doing when you hear these noises.

If you need it quieter, replace the old worn out carpet with some new stuff from ACC (www.50resto.com) but it won't change too much

 

[gt90stang]

Things to check:

1. When my front struts needed replaced I dreaded every small bump in the road....talk about harshness. After replacement no worries nice and I don't have to worry about every little bump. Problem is it just sneaks up on you.

2. With rear gear ratio changes you mess up the rotational balance of the driveline and pinion flange. This will be speed sensitive and repeatable on any surface.

3. Polyurethane bushings, motor mounts and spring cushions increase road feel and harshness. The price of increased performance and suspension firmness.

4. Exhaust and motor noise is greater with increased exhaust size and high flow components. Oh well, just get out of my way!

Bottom line it isn't a luxury car and was a low cost everyone's sports/performance car. It's not a BMW, Lexus or Vet...It's a Mustang and proud of it!

Don

 

[BullittAndy]

Carpet is new and is the type with the layer of rubber between padding and carpet. Good point on the struts and shocks, those are next on the list. I'm just curious if something may be wrong with MY car or is it "they all do that."
This particular car was not very well taken care of and I'm fixing the previous owner(s) mistakes. Thanks for the ideas and help, keep -em coming.

 

[Michael Yount]

The Fox unibody was not the most structurally sound to start with -- no comparison with a newer model Infiniti Q45. Are your subframe connectors welded in? Anything you can do to stiffen the structure will help. Roll cage is ideal -- but of course, that transmits a bunch of noise into the cabin as well unless you insulate it too....

Much of the noise in any vehicle comes from resonances related to the trunk/hatch cavity and what's under the headliner (underside of the roof). The roof and deck lid are like big drum heads. If you haven't insulated there -- and of course, that's difficult to do.

Manufacturers have invested billions in reducing NVH on newer cars. They're better at reducing it than they've ever been, and they've made huge leaps in the last 15 years.

I strongly recommend that you invest the rest of your NVH money on the Stang into a first class, powerful stereo system. When the creaks/rattles get to you - TURN UP THE VOLUME. You won't hear the rattles anymore.

 

[srothfuss]

Good idea about the stereo. I like to just put the top down so I can't even hear myself think.

BullitAndy - it's not just your car. The entire Fox platform is like that. And after 15 or so years of abuse, it won't get any better.

Edit: I posted without finishing my thought. ...get any better. As long as you keep replacing things like bushings, carpets, weather stripping, tires, bearings.... The car will come back to life. The noises have always been there however, even when the cars were new.

 

[Michael Yount]

Yeah - and with a vert r'fuss - you REALLY need to drown out the squeaks/rattles! Do you have subframe connectors? They really help the verts -- the hatches/notches are flexi-flyers; the verts are like overdone pasta.

 

[2002BLGT]

I will let you in on a little secret , its a mustang , its supposed to shake rattle and roll .........

 

[srothfuss]

Yeah - and with a vert r'fuss - you REALLY need to drown out the squeaks/rattles! Do you have subframe connectors? They really help the verts -- the hatches/notches are flexi-flyers; the verts are like overdone pasta.

Yeah, I have SFC's... but I don't have a strut brace yet. I'm working on it though.

 

[Strype]

Don't put new springs and 17's on it if you don't like noise... Whew!

I've had 2 verts (83, 86) in the past and my GT hatch is by far the worst about noise!!! Of course I kept the top down most of the time.

 

[BullittAndy]

thanks for all the replies. It sounds like it's not just my car and is inherent to the design. This saves me a lot of stress and money trying to make it perfect.
Its important to have a baseline to compare it to.
-Bullittandy