Tallman

Other than the "active handling light issue" (which I was fortunate to resolve myself with the help of this forum), our 2006 C6 with automatic transmission has been trouble free.

I have been concerned about the need to change the fluids (other than the oil & filter which has been changed every 3,000 [and more recently, every 5000] miles) with Mobil 1 5w30 synthetic.

We now have about 42,000 miles on the odometer and my concern is not the mileage as much as the time since delivery was on 10/28/05 so we are now approaching seven years since the car was new.

At my insistence, the mechanic who services our other vehicles and the oil change man who does the oil changes on the C6 (two different people), recently consented to change of the C6's coolant so that has now been accomplished.

I am now focusing on changing the transmission fluid & filter but the owner's manual recommends this procedure at 100,000 miles for a car in "normal service".

Reading the threads on this and other Corvette forums, the consensus for servicing the transmission seems to be in favor of drain & fill as opposed to flushing so I was contemplating doing the drain & fill.

Today I remembered we purchased a 2006 C6 service manual shortly after we got the car so I located the manual (still new in the box) and was surprised to find on page 7-226 that the "Transmission Fluid Fill Procedure" refers to using a "J45096 Transmission Oil Cooling System Flush and Flow Test Tool".

My mechanical knowledge is limited so maybe I am misunderstanding but it seems the C6 Service Manual is specifying a "flush procedure" with no mention of a "drain & fill" procedure.

I am confused as to which procedure is best and whether to even do any service to the transmission at this time.

Any helpful explanations or comments are appreciated.

RicK T

As you've already found out, there are competing opinions here vs. the recommended time and procedure. IMO the trans was designed to go 100,000 so if you simply check it regularly, as long as it is basically red in color (not brown or worse), doesn't smell burned and feels slick with no particles, it should be fine.

Problem with flushing is, there are several bad stories here about big problems after flushing. Theory is flushing stirs up bad deposits and distributes through the trans.

Some here say do a drain and fill at 50,000. Just more opinions. You have to go with what you're comfortable with.

JCtx

NUCH better to do 2 or 3 drain/refills, than a flush IMO, but to each his own. I'd have done it long ago, especially the first time, to get all the assembly and break-in contamination/deposits out. And remember almost anything qualifies as 'severe' duty, which reduces the interval to 60K-miles; make sure to read all the myriad situations which qualify the interval as such. Anyway, I assume with 100K miles, the fluid is fully synthetic, but I'd make sure of that. Manual transmissions do NOT come with synthetic fluid, so I'm about to change it to fully synthetic around the 3K-mile mark on the new GS. Along with the differential and engine, of course, but will stick with OEM fluids on those.

By the way, I personally think 7 years is too long for the additive package to hold, but if I were you, I'd certainly get a sample and send it to Blackstone labs (or similar) for piece of mind. That way you know if it's a wise decision to wait that long next time . Good luck.

AORoads

so, unlike the coolant (which says, replace at 5yr/100K miles whichever comes first), the trans fluid change says, 100K miles?

that's a question. I don't know the answer. because if it does say that, or not say anything else, then your trans fluid by the time you get to 100K miles, extrapolating from what you've done so far will have been in there about 14, 15 or 16 years. (seven years now from 10/05 inservice date, 42K miles)

seems like a long time, to me, for the same, old, deteriorating fluid from day one to be in the trans to make it to 100K miles.

as to what procedure, why not just check in with a dealer and ask what is their normal procedure for an '06? you're not asking them to do it, just what they would do.

VET4LES

Lot's of good advice and the only thing I will add is an old theory is when you get a lot of miles, how many is questionable, don't flush. It can break loose junk that can plug up orifices and cause problems you didn't have before the flush.

Gearhead Jim

If you search under my name; I just started a thread about having my A6 tranny, and differential; drained/refilled. Samples of the used fluid were sent to Blackstone Labs for analysis.

Both units had been drained/refilled at about 7k miles, and the recent drain/refill was at about 51k miles; so about 44k miles on the fluids.

Blackstone said the units, and the fluids, were in good shape and could have gone longer before the change. But since I did that initial drain/refill at 7k, that may have contributed to the good results on the recent analysis. Or not.

Unlike engine oil, the tranny and diff fluids don't get contaminated by combustion products, so I wouldn't worry about time, only about miles. Well, maybe after 10 years I'd change regardless of miles.

Tallman

Thank you for the excellent responses. I still feel drain & fill is my best option so will pursue that avenue. Since the drain & fill procedure will only be replacing a portion of the fluid, is it mandatory to use GM fluid or is Mobil Dexron-VI AFT ok? Thank you again.

RicK T

If you didn't see it, here's another current thread about the results of a 100,000 mile service.

http://forums.corvetteforum.com/c6-c...ult-6l80e.html

Mad*Max

when doing the filter change/dropping the pan, do you have to replace the gasket with a new one or can you re-use the old one?

HOXXOH

IMHO I'd go with the GM fluid. Although it's possible that Mobil packages the exact same fluid for GM and themselves, I've never been one to mix brands when it's not necessary.

I did a partial change at 55K and a full change at 71K. Assuming my transmission survives this next racing season, I'll do a full change again around 120K. Severe service and GM fluid every time. I'm not saying it's the best, but I'm not enough of an expert to know if anything else is better and I doubt anyone here is either.

Mad*Max

HOXXOH

The service manual says inspect and re-use. Worked for me.

Mad*Max

thanks

Rogers 07

The gasket looks like it was designed to be re-used (dont use any sealant on it) so if it's not cracked or torn re-use it !!

Mad*Max