If you haven't changed rear end fluid yet...do it !
 

Just did another z06. 673 miles and pull rear drain and oil has the normal sheen from breaking in plus magnet picked up little particles also normal.

If dealer or anyone says magnet was clean nothing on it I've yet to see that and I've done about 12 cars including mine.

3 quarts amsoil 75w-90 is what I've been using. I know it overkill but on mine I will change at 5k miles again just to do final clean up.

Very easy to change the rear diff fluid as stared on here 3/8 extension 12 inch will take care of bottom drain and then the fill I've been able to use a 3 inch 3/8 extension angle it right behind the swaybar in and just grabs the fill nut come right off.

Oh also I clean out as much as I can with brake cleaner on fill up top just use the little plastic hose to spray around and then on the drain hole do same thing and also I have the rear end fluid warm when I change it.

people have been saying the amsoil didn't have the friction modifiers that the GM fluid had so I have been using that. Any thoughts on this because I would rather use the Amsoil if it were correct.

Thanks. This is definitely on my to-do list for the winter along with some fresh transmission fluid.

I've yet to have any issues and I have 75w 90 amsoil in my car also. If I do hear any chatter I will update this thread but so far my car and others have been fine.

Oh and I jack the front up on the car a little to make it drain easier.

The owners manual states that the rear differential isn't due for a change until 45,000 miles!
Why are you changing it so soon?
Doesn't GM take into account any particles that might be in the oil for change purposes?

I never trust gm oil change schedule. All my cars oil at 500 then at 2k then change every 3k after.

Rear end 500 miles and 5k mikes then after every 20k.

Maybe over kill but there's no way on a z06 I'd wait for 45k to change rear diff fluid. This is just my feedback on over 10 I've done myself. Dealer charges way to much money also for rear diff change

My rear end grenaded at 500 miles, so I didn't make it to the first change!

Can you summarize the process? How's access? Are there separate drain and fill plugs, or how do you get the old stuff out?

I had mine done last week at dealer with 7K miles on my 2015 Z06, oil was dirty but not much on the magnetic drain plugs.

How I feel about it.

So it gets dirty. The diff might blow? eh, thats what the warranty is for.

I lift car up a little in frint so slopes back
Make sure rear is warm
Take off fill plug first
Then take off drain plug
Stuff will pour put
Get brakes cleaner and clean out as much as you can
Put the drain plug back in
Fill unit up till comes out
Put in fill plug
Make sure both tires off ground start car up and put it into drive and I let it run for 30 seconds
Then turn car off and recheck oil level and fill if needed

Mine was changed at 9k 2 weeks ago. Car going in a couple of weeks to have another 200 plus hp added. The tranny and diff are going to be pushed anyway so early fluid changes for me.

I would be careful about substituting a fluid with potentially different friction modifiers. The car PTM systems and E-diff parameters are all calibrated to the fluid characteristics ( in addition to the tire behavior etc etc). Changing any variable here might degrade performance or result in some unwanted behavior at the limit...

4 of the guys road race no issues with amsoil

Myself I street race and no issues

Ediff so far no problems with amsoil and if I got feedback saying there were issues from any of the cars I've done I'll post up.

Unless you track the car. But I would change it annually regardless. About $150 is cheap insurance IMHO.
Bish

I second NORCALSS on this one. My car's been at the dealer for a week getting its diff replaced; it went at around 1,200mi. I would definitely recommend changing the fluid with the break in oil change and I plan on having it replaced after I have 200mi or so on the new diff.

OK thanks, good to know. My comment was just a general caution. This car's systems are so specifically programmed to extract every ounce of performance out of the whole system, that I would be reluctant to change anything.

I am 100% with you on not observing the factory periodic change schedule. At the very least, take the plug off and see what metal might be there or what the fluid level is.

I picked up my car in Montana (courtesy delivery). I actually had the dealership put 200 miles on the car before I flew up to pick it up and do that first oil change, and had them check the diff before (to make sure it was filled) and after the 200 miles for metal. I have brought the car back with 2,500 miles and will be doing another fluid change and inspection of the oil and diff fluid shortly at my expense.

I changed mine at about 1500.... When they installed a new transmission.. :(

Shaking my head.....to say you have gotten no problems yet, you sample size nor method of analysis leaves a lot to be desired....it's like playing Russian roulet....I keep pulling the trigger because the gun hasn't gone off yet....

By the way, I do agree with changing it at a period after breakin.....just not your lubricant selection....

If I have issues I'll report back. Amsoil has worked well for me and has worked great on the c7 z06 I've done.

Oh make sure to put the car in gear and run it when you first pump it in. Little more will go in when you recheck it

I have to agree. A small sample size and method of analysis may lead to unexpected outcomes. This early on, I would just put the fresh GM lubricant/equivalent back in, especially since he stated he would change again at 5000 miles. Lubricant tests take many, many miles of run time to determine what works and what doesn't.