Hey Guys,

I just hit 30k on my 2009 C6 and the dealer is recommending a rear differential flush - it sounds unnecessary to me this early on. Thoughts? How often should this fluid be replaced?

Thanks,
V

 

No mention of changing the differential fluid in any of the maintenance schedules I have found.

 

Depends on how you drive the car really. I beat on mine regularly so it gets changed regularly. I've seen on three C6's now that the diff's leak from the breather for no apparent reason. Dealer says this is normal but I can't understand why it would be normal to leak anything unless overfilled of course.

Might be a good idea to have the level checked at a minimum.

 

vbadhwar,
I've not seen anything regarding there being an actual maintenance schedule for having your rear diff fluid changed. However, there have been numerous reports of rear end noises that have been alleviated by having the rear diff fluid changed. Also, depending on how you drive is is a good idea to have it changed on occasion. This might be what he was getting at.

Chevrolet Customer Service,
Justin

 

Nothing in the book, and 3 yrs/30k miles sounds like a ripoff unless something is getting noisy.

I had the dealer change my diff fluid at about 7k just to get the manufacturing crud out, and plan to do it again at 50k. But if the dealer told me to do it, I'd be saying WTF...

 

After dealer changed diff clutch discs at 20k miles, I did not change fluid until 96k miles when I drained and filled with the "new" GM fluid that has additive in it already.

The new fluid did not work too well, since it recently got so noisy when making tight turns I thought my bearings were toast. But noticing the noise only happened when I was giving some throttle while tight turning vs. no noise when tight turning without throttle, I thought it may be the fluid.
So after only 30k miles at 126k miles, I just changed to Royal Purple Max Gear Oil (also has additives in it already) last week and it's back to being quiet and confirmed bearings were not the issue.

Interestingly, leaving a parking lot after doing only 4~5 figure eights [security showed up at that time to see what I was doing], the Active Handling acted up and buzzed/braked the car to a stop. It kept doing this while I tried to leave the area, until after half dozen AH stops, I shut off the car thinking the figure eights must have worked too much of new and old additive or whatever into the diff clutch discs and needed to be cooled down. Upon start up, everything was good and ok for a week now.

Anyway, if your diff is quiet, I would not change it, since the "new" GM fluid they put in will probably make it noisy sooner than keeping what you have in there.

 

If it has never been changed, I would change the lubricant and use GM Dexron LS 75w-90. Limited slip differentials require more frequent service than standard differentials.

 

change every 25 to 30k

its about as quick to do as an oil change. might as well diy.

 

There is no need for a diff flush. However, there is nothing wrong with doing a simple drain and refill with DEXRON LS or other premium fluid every 30k or so miles. It won't turn into a pumpkin if you choose to use a longer interval. JMHO.

 

If you haven't been taking your car out on a road course you don't need to change it very often. The latest GM requirement for cars running in track events is to change the diff fluid after every 24 hours of track duty.

I wouldn't worry about it.

Bill

 

I have also heard that if you switch to a different gear ratio, you should change your dif fluid more often. (every year?) Any thoughts on this?

 

I change mine every year, which is about 5,000 miles. I have 4:10 gearing with some upgrades from stock and this is recommended by the builder, DTE Engineering. My other cars I have always changed at 30,000 miles all fluids included.

 

Do you know why they recommend shorter intervals just because the ratio changed?

 

Not sure, but I know the clutch packs wear and let off particles contaminating the fluid.

 

Not sure, but I know the clutch packs wear and let off particles contaminating the fluid. Also consider about 20% more wear per mile with my ratio.

 

I change all of my fluids every 30,000 miles or once a year, plus a new filter for the A6.

 

Just changed the fluid in mine and now it's clunking during slow turns. It's never happened before. I used the same Amsoil Severe Gear 75w-90 I've used before, did the figure 8s, etc. The only thing different is I only had about 1/2 bottle of the additive. I have to assume this is the issue? Ordered a couple more bottles but is there any danger driving the car in the meantime?

Should have just left it alone...

 

Probably not enough additive - the C6 diff really seems to need more friction modifier than the C5 and prior Vettes. I've been running the AMSOIL Severe Gear Extreme Pressure Synthetic 75w90 (Product Code SVGQT) in my 02 Z06 and ran it in my 06 CTS-V from 06-09 (when I sold it) without extra additive and neither diff chattered. But most C6 owner's report chatter without a bottle of the AMSOIL Slip-Lock Differential Additive (Product Code ADATB). So I'd add another half bottle of this and see if it improves. The chatter is not reported to cause mechanical problems with the diff as it is just the clutch plates sticking and releasing instead of sliding over each other, but I've never experienced it so can't talk from personal experience. Note that adding too much modifier isn't really good either as when the clutch plates slip too much your limited slip diff is less limited slip (e.g. more like an open diff).

For the OP, there is no "flush" of a diff - just a drain and fill. I personally do my cars very early after I buy them and I change the diff fluid in my Vette which I run only at the track at about every four track weekends. I sampled the diff fluid in my 06 CTS-V when I drained it at about 10k miles and the lab's analysis was that the change was a good idea:
2006 Cadillac CTS-V Used Oil Analysis Factory Fill Differential Fluid.

 

It's the same fluid I've always used and I have never had issues before. Like I said, the only thing different is the amount of additive. It's more clunking than chattering. Hopefully the remainder if the additive will fix it. Thanks

 

i am going to change differential fluid and manual transmission fluids....do i need to know any special procedures?thanks j.k.