MustangGTCS13

Alright I was wondering if anyone else has experienced a whine or humming noise that sounds like a window is cracked, but comes from the back center of the car. I had the car lowered by a professional Mustang shop with Eibach Pro Kit lowering springs, BMR adjustable panhard bar, and BMR rear poly control arms.

I've called the mechanic, had him double check the work and talked to American Muscle about the issue and BMR. I keep getting different answers. Some say the pinion angle might be off, but others are saying the new bushings on the better setup are transmitting the noise from the driveshaft into the car. I just don't want to continue driving the car if it's a problem and is causing issues.

The noise is always present from anything from 5mph and up and yes I have searched the you know what out of the forums, but nobody describes what you'd hear or feel if the pinion angle was off compared to normal noise from the bushings. I've read this link...cherod.com/mustang - LCAs

and it makes me believe that the noise is normal, but if it is, is there anyway of dampening the noise? Dynomat in the trunk? Please help me figure out what noise is. Keep in mind it's present at all speeds and the car doesn't vibrate or feel off.. in fact the lash I had before from the 2 piece driveshaft almost seems to be gone since the upgrades. Only noticed this after I did the above mods.

dusman59

Almost every mod with stiffer bushings will add noise. The one piece DS will add some also. Even the tires will transmit noise through a stock setup let alone a moded one. I used Second Skin with closed cell foam over the entire rear seats, trunk area and quarter panels. It did help some but did not eliminate it. The biggest improvement was the shaker 1000 sound system as it tighten it up and allowed me to play it much loader without distortion. The disadvantage is it added around 50 pounds. I only street drive my car so the weight increase didn't matter to me.

MustangGTCS13

I was just curious if the noise was normal and how you'd be able to tell if it's a pinion angle issue compared to just normal noise. Any idea?

Jay@Hypermotive

Are you a manual or auto? If manual do you have the WL trans bushing installed?

MustangGTCS13

I have a 13' manual GTCS

AMDanBailer

This could be a few different things. You're definitely on the right track, though. It's absolutely related to the stiffer bushings and the pinion angle. If you don't have an adjustable upper control arm at this time then the pinion angle has to be off a bit. I installed almost an identical set up on my car and got a vibration above 100 MPH. The moment I installed the JPC upper control arm and adjusted the pinion angle it completely went away!

I would throw an upper control arm for a few reasons. 1 - you can set the pinion angle. 2 - it will help you at the track and is much nicer than the stock unit!

If you still have some noise after this, I would be willing to bet it's just normal stiffer bushing sound. A little dynomat in the trunk or under the rear seats should help with that!

Hope this helps. Now remember this is just my recommendation and experience with the issue!

-Dan

MustangGTCS13

Dan,

I was contemplating getting the upper control arms, but some say that since the upper control arms mount right by the rear seats, any further noise will just be amplified. I'm going to have my mechanic measure the pinion angle this week or next to see how far off it is, but i'm concerned upper control arms may not fix the issue. I don't believe I get any vibrations at any speeds, but is that a sign of the pinion angle being off? Just trying to decipher if it's a pinion angle issue or driveshaft vibration being amplified by the bushings in the new lca. Thank you Dan!

Stevedotmil

You can download a free app from TREMEC to an Apple device that will do the same thing.

AMDanBailer

I would start with checking the pinion angle for sure. This would be the first step of troubleshooting in my opinion! It's normal to get some added noise from those bushings that you added. However, I think if your car is lowered, you have a 1-piece driveshaft and don't have an upper control arm - it's almost a guarantee that your pinion angle is off. I didn't get any added suspension noise when adding the JPC upper.

Definitely check that out and let us know how it goes!

-Dan

MustangGTCS13

Dan,

I'll measure the angle today and see what it comes up with. The driveshaft is a two piece stock driveshaft. I heard there won't be much of a issue with a two piece instead of one.

AMDanBailer

Ahh! I was under the impression you had a 1-piece. That changes things. The stock 2-piece shafts definitely allow for more flex and shouldn't really be humming to bad. However, the pinion could still be off pretty bad. You'll just notice it much more with a 1-piece.

Let us know how it looks!

-Dan