I had my diff replaced under warranty, 15 z51, and this new one wines fairly loud on highway goes away when I let out. I'm at about 200 miles on it but noticed it right away. Is it something that'll go away after some more miles and a fluid change or do I need to go back to the dealer and be out a car again for however long it takes to fix.

 

I'd take it back.

 

If I don't break it again after this coming weekend I probably will

 

They generally don't get quieter with age. Sounds like time for another trip to the dealer.

Keep in mind that the diff gets VERY hot during the first few miles of operation so be gentle with the new one, especially for the first 50 to 100 miles. No sustained high speed driving and a few short trips of gradually increasing length during the first 100 miles are optimal.

 

I'm not sure what they did with it after replacing, I had a 10 minute drive home took it easy interstate speed. Followed by back and forth to work taking it easy around 15 minutes each way. Was very easy on it for the first 200 miles or so but it whined from the second I pulled outta the dealership. They are aware of it just told to drive it some it's still pretty tight.

 

I build a lot of transmissions and differentials in my "other" life, the noise is NOT going to go away. If the sound changes pitch at constant speed while going from slight acceleration/coast/slight decel then the issue is with the ring and pinion, specifically pinion depth. If a roaring sound only changing with road speed it would be a bearing.

I would get them to send another diff and schedule a service visit

 

Take it back, whine, especially load sensitive wine is caused by pinion to ring gear misalignment. These are hypoid gears, this means that the pinion is not properly aligned with the center of the ring gear (like a bevel gear) but is placed parallel to, but lower than the centerline of the ring gear. This requires that the pinion align precisely with the ring gear teeth, matching the pattern that the gears were cut. If the pinon depth is off, they will whine, and usually, the volume will be load dependent (light coast or light acceleration. will change the volume). If it is really bad, it will whine at all load levels. More miles will not silence the noise. I have set up numerous rear axles, if the pinion depth and backlash are set correctly, they won’t make any noise, even when brand new. Also, as previously stated, proper break in is important as well, but not for noise control, for long-life (and I guess end-of-life noise control). On a lightweight car like the Corvette, drive for 1-2 miles at 30 MPH, then perform 20 to 30 moderate 15-50 MPH accelerations (NOT full throttle), then park the car and let the rear end cool (2-4 hours). Then drive it nice, avoiding constant speeds or full throttle acceleration for 500 miles and you are good to go. Note that race gears are “softer” therefore do not require the 200 mile drive-in, but they don’t last as long as street gears. It also is not a bad idea to replace the fluid after the break-in, but the factory fluid is not replaced after the stock gears are broken in.

 

I feel like maybe some of you guys should do it for this tech lol. It could just be an honest mistake. I appreciate all the info if it survives this weekend I'm going to try to get them to order a new one for me.