2014 Mustang Rear End Gear Change V6 Auto - Whine And Vibration

[M Bishop]

Hi all, I really need some help on my 3 month old Mustang V6. I got a really good deal on a new 2014 Mustang V6 Auto Mustang Clubs Edit. The car came with a 2.73 rear end gear which as you probably know, is horrible. I had a local shop replace the gears last week. I used a kit from American Muscle which included 3.55 gears from Ford Racing. Here is where things went bad. After about 200 miles now my gears whine (more noticable between 40 and 65mph. Not loud but I can clearly hear it. And,,,the bigger problem: at speeds above 65mph the car has vibrations. These are probably two different issues but I am hoping someone here can give me advice on what this could be. Its going back to the install shop tomorrow. The vibration is the larger concern. i I could live with the whine but after paying $550 (not including parts), shouldnt I expect no whine and no vibration?

Some say gear whine is normal but most say its not. Vibration is an issue I know.

Thoughts?

 

[Svtpilot]

First off make sure everything is tight.Something could be have been left loose. Barring that, typically a whine after a gear replacement indicates a bad pinion bearing or an incorrectly set backlash. The vibration could be a bad pinion bearing as well . It can also be from your drive shaft. With the new gears the drive shaft now rotates much faster and has to be balanced to a higher rpm. This was a common issue with the fox Mustangs after a gear change. I have never heard of it with an S197 Mustang so its probably not your problem but that is what it sounds like. Bring it back to you mechanic, I assume he is reputable or else you wouldn't be using him, and let him have a look at it. Good Luck!