Reducing NVH (Noise, Vibration, Harshness)

bmpweXJ

bmpweXJ

NAXJA Forum User
Location
Denver
There's tons of info on this site about building XJs that are more off-road capable, but very little in terms of making our Jeeps more comfortable. I'm hoping to start such a discussion.

Why I'm interested:
My Jeep sees ~90% road use, 8% gravel road, and maybe 2% actual off-road use. I'm not interested in buying another vehicle that I have to pay for a note, insurance, and parking (~$150 /month where I live). So... I'm interested in what can be done to make the XJ a more comfortable vehicle to own/drive.

I'm sure there's a lot of other owners on Naxja that are in a similar position, so lets talk:
 
I'll start with some of my own thoughts:

Noise
Sound deadening. I've bought some spray on sound deadener. Not the rubber stuff from Autozone, it's something like this.

Vibration:
Rubber. Rubber. Rubber. I've got rubber bushings all over. Browndog motor mounts with the rubber bushings. JKS control arms. These have gone a long way towards making the ride nicer.

Harshness:
Getting your drivetrain angles fixed. In my opinion, anything over 3.5-4" is too high for short arms. Get some drop brackets or long arms and fix your angles.

Also, buy an appropriate load range tire. If you don't need a E range that can cary $3k lbs, why put up with the harshness that goes along with them.
 
bjoehandley said:
Honestly, it is a Jeep and an off road vehicle that was first came to market in the mid-80's, I just live with it.
Click to expand...

Thanks for the great contribution.
 
The 3 best things I have done to improve the ride of my (About 4" lifted) XJ were installing standard (load rating C) tires, R/C drop brackets & installing WJ lower control arms. The WJ control arms were a big improvement.
Google “wj control arms on an xj" & a bunch of articles will come up, I got the Idea from Go Jeeps site.
 
garr said:
The 3 best things I have done to improve the ride of my (About 4" lifted) XJ were installing standard (load rating C) tires, R/C drop brackets & installing WJ lower control arms. The WJ control arms were a big improvement.
Google “wj control arms on an xj" & a bunch of articles will come up, I got the Idea from Go Jeeps site.
Click to expand...

How have the WJ arms held up? Does your XJ get flexed often? Do you think the improvement was due to the rubber bushings?
 
I have TNT long arms on my Jeep. These arms use poly bushings at the frame end. My set up is about 5" of lift so my arms are very close to parallel to the ground. I still find there is harshness transmitted.

I noticed that Ballistic makes a rubber johnny joint style bushing that might be able to replace the poly joint without doing any fabrication. I've been meaning to see if it fits but haven't quite gotten around to it.

Also, I am getting quite a bit of harshness from the rear springs. My lift spring and shackle combination is about 5" also but my shackle is almost vertical. I've been meaning to get some aftermarket shackle relocation boxes to dial in the back end. Just haven't gotten around to it.

My OME dampers seem to have a valving rate that doesn't work well with my RE springs. Not sure what to do in this case. Adjustable dampers seem so gimmicky.

The anti-roll bar geometry on my Jeep needs to be changed also. The angles seem to fight each other with articulation.

Interior wise, paint on sound deadening, doors, firewall, rear quarters, roof, etc. is all going to be done.

I also want to get a sound/insulation blanket for the underside of the hood.
 
Last edited:
Much has been said about suspension mods to decrease nvh, but you may also want to look into your motor mounts. Engines cause a lot of vibration, make sure your motor mounts aren't worn out or broken.
 
I like Brown Dog mounts, but if you like no engine feeling don't get them. Even their rubber ones transmit more vibes than stock. Don't use any poly bushing anywhere.

Use some sound deadening material on everything you can get to.

Use a softer shock.

Get a hood pad. Some years didn't come with one. There are better aftermarket alternatives though

No cai as that introduces noise, stay with the stock air box... same with the exhaust.

Replace your weather striping if its in bad condition.

Frame stiffeners will help with squeaks over bumps and turns.

Get a good road or AT style tire.

If you want to take your dash apart put friction tape every where you can

Stock comes with a plastic or rubber shield between the door and trim. Make sure it is present and fastened down well.

Position you roof rack cross bars where they make the least noise... or just remove them.
 
I have Heim Joints in my suspension, (Control arms, steering) Talk about noisey, Mine are pretty bad, but I have learned to live with them. But I have thought about adding some rubber between the mounts and the heim joints to prevent them from hitting each other.
 
Root moose:
Can you link to this rubber joint? I've looked around their site but all I found was: http://www.ballisticfabrication.com/Ballistic-Forged-Poly-Bushing-263_p_1646.html This doesn't seem to be what you're describing.

Talyn:
I'm going to be tearing my dash apart to replace a bad evaporator before it gets too hot again. I'm planning on adding sound I solution while it's apart. I've never heard of friction tape, what is this?
 
Its a cloth tape that has adhesive on one side. Similar to the red velvet looking stuff you will find. It goes between two pieces to reduce rubbing noises. I don't remember where I got my role.

Also, since you have it apart put some sound deadening under the top of the dash. There is some there already, but I bet it has fallen away from the dash. And put some against the fire wall as well.
 
Under the top as in on the backside of the plastic dash?

I plan on hitting everything pretty well back there. I also plan on fixing the stereo ground, squeaky steering wheel, evap cooler, run a 1/0 wire through the firewall, and upgrading the dash to LED lights while back there. I don't ever want to open it again, so I figured I'd hit it all.
 
pull the dash, pull the seats and carpet, pull every interior plastic piece you can, pull the headliner. I use a product called noisekiller (not even sure if they make it anymore but i got it in a 5 gallon bucket and it's lasted me years) it's basically a rubberized roll or spray on vibration dampening material. I put it on the back side of all the plastics, along the entire floor and firewall, the back side of the dash, inside the doors, on the inner roof skin, basically every bit of metal you can see. once two thick coats have gone in and cured I like to lay sheets of dynamat out, mainly over the firewall and the large open sections of the floor and roof, as well as the doors and the rear quarter panels (where you can reach through the access holes that is).

I've done this to 2 XJs mainly to get rid of vibrations for big subwoofer applications but the same ideas apply to reducing road noise. Afterwards they are quiet enough to whisper on a cell phone on the highway. having good condition weather stripping also plays a huge part in this as Talyn mentioned.
 
Root Moose said:
Also, I am getting quite a bit of harshness from the rear springs. My lift spring and shackle combination is about 5" also but my shackle is almost vertical. I've been meaning to get some aftermarket shackle relocation boxes to dial in the back end. Just haven't gotten around to it.
Click to expand...
I've got a set of RE 3.5" leads that sit exactly 4" and ride very harsh. My shackle is fairly verticle. I plan on going to the OME 2.25, relocation brackets, and whatever size shackles I need to get back around 4".

Can someone explain how the shackle angle affects the ride of the springs?
 
They're also called flex discs. It's one of these:

113549.jpg


That goes here:

16gz9sl.jpg


It would take some modifying or finding the right part to fit our flanges but it would certainly make a difference.
 
You must log in or register to reply here.

Similar threads

A
Vibration after rebuilds
Replies
17
Views
1K
asymptonic
A
C
Seeking Tuning Advice for Gen 1 SVT Raptor Shocks on a Jeep XJ
Replies
1
Views
181
Evan03
E
G
2000 xj Where to start
2
Replies
28
Views
2K
Jeepedo129
Jeepedo129
1
Feeler for sale of my XJ crawler.
Replies
0
Views
465
1-tonxj
1
R
Which steering box brace? Bearing or not?
Replies
7
Views
3K
75SV1
7
Back
Top