There are several differences. The rear end is turning much higher rpms due to reaching speeds that are at least double what you see on the highway. When the car isn't at top speed it is straining to get to top speed thus there is more power being transferred through the gears as the car is accelerating at full power Vs the very light load conditions of driving on a highway. The drive train isn't 100% efficient so an increase in power being transferred through the gears means there is an increase in heat as well. Due to the near continuous WOT or near WOT operation the exhaust gets much hotter and transfers more radiant heat into the drive components it is near. This doesn't go on for short periods of times either. Racers typically run 30 minute sessions. People who do HPDEs probably put more track time on their cars than racers. For example, from April 30th through May 8th I did 5 track days and put 440 track miles on my C6Z at speeds that got to over 150 mph at least once per 3.4 mile lap.

That is why they put tranny and diff coolers on the Z51, GS, Z06 and ZR1s. The guy who putt putts down the highway at near no load conditions doesn't need them but the track guy does.

Bill

 

I guess I have one more thing to look forward to prior to upgrading anything... YAY!

Any ideas on a general going rate for diff fluid servicing and trans fluid/filter (A6) servicing at a dealership?
Im trying to figure out how much of my tax check Im going to be able to spend on fun parts...

 

At 70k miles my car is running stronger than ever with the fluid it came with and just turned its best ET yet.

This "rule of thumb" maintenance is as good as the brake fluid thread.

This forum loves to quote the manual like it's the Bible,...except when it isn't convenient

 

Never thought of that, good point!

 

I don't think that anyone has ever said that your car would get slower as the gear oil sheers down in viscosity. In fact the opposite is true (less friction loss from churning the lower viscosity oil), and some gear oil manufacturers go the route of going with the low end of the allowable viscosity while boosting other wear additives to get better racing performance comparison tests.

All these lubricants sheer down over time, it's the nature of how they work. But wait long enough and you've just got a container full of short HC chains that will no longer protect the machinery as well any more and you are left with relying on the various additives for last resort metal-metal contact protection.

Today's car manufacturers have figured out that you can get a car to 100K without changing the gear oil, and just doing a few engine oil changes. What happens after 100K isn't their concern, since most buyers have moved on by that point, and car manufacturers are not in the business of pleasing used-car buyers.

You do not need to change the diff oil, but it will be true that whatever lifetime the diff has, it will be shorter with no changes than what it would be with them. This difference may not have any impact if you don't plan to keep the car long enough to find out.

I do these kind of maintenance things, but really, I will probably never accumulate enough miles on the car before I move on in a few years to whatever I fancy next, for it to make any difference to me.

 

Although you may drag race, it doesn't sound like you do a lot of road racing(one deduction being an auto) FWIW my FRC has 112k miles hard miles on it. As member TLK and mneblett stated in the other thread, there are reasons behind fluid changes and you should look at the overall picture and not just make a generic blanket statement of course.

 

GM no longer specifies an additive to the differential lube and in fact the last TSB specified not to add any friction modifier to the lubricant. see the following which specifies Dexron LS Gear Oil 75W-90 (P/N 88862625) only.

http://forums.corvetteforum.com/show...73&postcount=4

 

Yes, I've had several fluid changes in my 2009 C6 for one reason or another (4.10 gears, noises, etc.) and all the changes were with the new fluid that requires no friction modifier. With the new fluid, I never had any noises, chatter, etc. so it appears that GM did get the mixture correct and you can just use it alone now.

 

Yes, 30K...really.

 

I change my diff and A6 oil and filter every 20,000 miles. I have over 110,000 miles on my 07 with no problems yet, but as always each to their own.

 

Outstanding to see that you are driving your corvette!

 

Thanks, its a great car! No matter how bad or stressful my day at work is, the drive home is always nice & relaxing.

 

My sentiments exactly. Ever since I started driving modern era vettes nearly 11 years ago, every work day is a good day from the moment my eyes open in the morning because I know I will be driving one of my vettes to work and back. It matters not what happened at the office!