diitto

Hi, It was conveyed to me by a Chevy service manager that it's a good idea to change the fluid in the differential and the manual transmission (I have a 6MT) every 15,000 miles. But my Owner's Manual NEVER shows changing these fluids. I don't own the Service Manuals but just the Owner's Manual with its Maintenance Schedule. And that Maintenance Schedule does not mention these fluids at all.

What do folks here think about changing those fluids??? Trying to understand why those fluids aren't mentioned at all in the Owner's Manual. I have a 2012 GS 6MT convertible.

Thoughts??? thanks...

BigMonkey73

I don't have service manual, but plenty of folks around here keep their fluids fresh. On those 2 items, once a year is about on par.

I do so because I road race and change fluids before new season starts despite mileage. If I only drove it around town and never really pushing it super hard, I'd say 15-20K sounds about right.

diitto

thanks for the feedback... yes, I should have said I am just an "around town" driver, going on occasional road trips with a local Corvette club. But no racing.. bob

Bruze

Ha, I'm sure the dealer would love to change everybody's every 15,000 miles.

I'd go 50k or longer. They're not like motor oil that gets contaminated from the combustion process.

Corvette_Ed

50k is about right for an around town cruiser.

revilingfool

transmission fluid you will start to feel. I would say around 30k miles between changes on most cars i begin to feel it.

Boomer111

I think the tranny can go longer easily MN6. I have changed my tranny fluid 3 times in 40,000 miles. But it has been over 9 yrs.

For information when I received my DTE rebuilt diff with the 4:10's they suggested diff oil change yearly. Which I followed for 5 years. Now I do it every other year. The Amsoil 75-140 still looks golden when drained.

I read somewhere once that oil when in contact with metal will deteriorate even without heat and wear. Now I offer no conclusive proof of this. Just what I go by and I always use synthetic oil in everything.

I change my engine oil yearly, lately with only a few thousand miles on it. Amsoil 5-30 Signature.

Do what makes you comfortable.

Car is only seeing maybe 2500 miles a year now though.

FortMorganAl

I'd like you to send me $150. Cash only, please.

I have the shop manuals and there is nothing in there about changing fluids that isn't in the owner's manual. The GM recommendation is to NEVER replace the differential or manual transmission fluids. There is nothing going on in those components that would significantly contaminate the oil or remove additives. Differential fluid does need to be changed once if you have a pre 2009 car and have a clunk in the rear when making slow turns. Do a search. The newer fluid solves that issue permanently.

Your dealer, like most, assumes you are an idiot who never reads a manual and can be talked into letting them do unneeded maintenance. Some dealers (like the one closest to me) will even charge you but not actually change anything hoping you will just assume that the work on the bill was actually done. They can get away with that since they think you won't crawl underneath to check and will never notice the difference. Find a new dealer.

TxLefty

Very rarely does anything fail from having fresh lubricants. That said, I changed my transmission fluid in my Cobra about every 30k and the rear end every 20k. But I drove it like I stole it.

cmonkey713

This sums it up!

Bruze

What you are "feeling" is probably the placebo effect.

extrapilot

I should change mine soon (diff) as I'm creeping up on 50K miles and the rear is starting to clunk on tight turns in reverse.
Not sure about the tranny, MN6, but I know that in my motorcycles, when I changed the oil, they would shift noticeably smoother, not certain that would happen in the vette.

Gearhead Jim

Lots of variety in the opinions. Here's a couple of facts:

1. The Owner Manual and Service Manuals do not recommend ever changing the diff fluid. However, those same manuals don't recommend ever flushing the brake fluid; which goes against the recommendation of some other car makers and all trackheads.

2. On our 2009, I had the diff fluid drained/refilled at ~10k miles to remove any manufacturing/breakin crud. Then at 50k I had it done again and sent a sample to Blackstone Labs, who said both the fluid and the differential itself were in excellent condition, I should go somewhat longer before the next change. I don't know how the 50k analysis would have looked if I hadn't done the first one at 10k. They did not tell me to never change the fluid.

As TxLefty said, it's rare for fresh fluids to ever cause a problem.
Just besure to use the newer version that GM started putting in the cars in 2009, it's called Dexron LS Gear Lube 75w-90.

But as others have said, your dealer is either grossly incompetent or downright crooked.

LowRyter

my diff was "clicking" when I made sharp turns. The fluid change plus GM additive fixed it.

The diff seems to want attention in these cars.

Bruze

That wasn't because the oil was "dirty," it's because it was the wrong oil.

C6 Snowboarder

I change my tranny and differential fluids about the same time I change the battery acid. I feel the doors open much better with fresh battery acid. Oil changed anytime the temperature varies more than 20 deg F

BTW - have not had any problems

Bruze

I have a banana every morning, I'm old, and I have no heart disease.

Therefore, eating a banana every morning prevents heart disease.

EDIT: Dang I forgot! I didn't have one this morning -- ate my last one yesterday! If I don't post back here, you'll know I croaked of a heart attack this afternoon. I hope I can get to the supermarket in time . . .

Corvette_Ed

I changed my battery acid two weeks ago. I also decided I'd go ahead and swap out my battery acid container at the same time as it just felt like the right thing to do.

CadVette

Change it! When I purchased my car at 35,000 miles I asked the owner if he had ever changed out the transmission and differential fluids. He looked at me with a puzzled look on his face and he was an engineer. Knowing this I changed out fluids in both. Upon inspection the transmission fluid was a dark brown color instead of the bright pink that A.T.F. is supposed to be. The differential wasn't as bad but he did say he had that changed due to a clunck in the differential while truning at low speeds.

windyC6

May be that nothing ever fails from having fresh fluids.....but having fresh fluids doesn't mean something won't fail for some other reason.....