This should be simple.... it ain't! I've searched every thread I could find on this site, and read Corvette Central's excellent write-up on changing these fluids. All it got me was confused. I'm planning to use GM fluids... not interested in competing brands (for simplicity)

Here's what I found:

Transmission:

Use Dexron III (GM 88861800)
Do NOT use Dexron IV (4)

Interestingly, Corvette Central says all C5 and C6 transmissions, manual or automatic, should use the new Dexron VI (6). ??

Differential:

Reading the posts, I found three different part numbers:

GM 89021669 75w90
GM 89021678 75w90
GM 89021677 75w90 (from Corvette Central website)

Use Dexron LS slip-lock additive- can't find a GM number.

Seems if I use GM Dexron III for the transmission I would be good.... not sure about the Diff....

Can anyone help with the latest GM Numbers? Also, how much slip-lock (Dexron LS) should be used?

 

What year is your car?

 

Sorry.... 2002 conv. MT

 

Dexron LS slip-lock additive # is 88900330 (4oz)
Older diffs held nearly 4qt and used 8oz of additive, C5 diff holds less than 2qt so only 4oz. The additive is used with 89021677.

A newer fluid #88862624 contains the limited slip friction modifier in it.

 

Thanks, I'll check with the local Chevy dealer tomorrow, see if they stock the newer differential fluid you mention.

Guess I'll go with Dexron III in the transmission.

 

I went through this ordeal back in the winter. I used dextron lll in my m6 but later some said it really wasn't lll so i drained it and went with amsoil, cost me about 80 bucks and the om says it doesn't ever need changing but i thought i knew better, dumb butt. I didn't touch the differential after this ordeal. I deviated from my theory, if it ain't broke don't fix it. My advice is leave it as is, nothing wrong with what is in it at present.

 

I respectfully disagree. There's no substitute for good maintenance, just as long as you use the proper parts/fluids/procedures. Having said that, I've changed the transmission and differential fluids in my '01 coupe twice, in the 14 years I've owned the car....and it has only 25,000 miles on it.

 

I run Amsoil in my 02 MN6 as well. Never had an issue with it and it shifts good.

 

Again if the owners manual states that it isn't necessary to change the M6 fluid why would we think we know better, I don't get it. I haven't read enough on the differential so I can't comment on it but I would guess the OM may state the same thing. If U know better than GM who designed the car and it makes U feel better to do the fluid change have at it.

 

They are dead wrong. GM released a notice saying do NOT use Dex Vi in any GM manual transmission. They sell their own manual transmission fluid for the M6 - but any "real" Dex III will do the job.

Re part number confusion, the problem is they change over time. Owners and repair manuals may well have different GM part numbers depending on the year they were printed. Originally, the rear end fluid needed a friction modifier - later fluids have one already in the oil.

As an aside, I never use dealer fluids - in my experience, they are usually overpriced compared with good brand names, and service at the parts desk is usually "off hand" to say the least.

I run Mobil 1 in the engine - though these days I run the HM version, Valvoline Dexmerc (a Dex III) in the MN6, and Mobil 1 LS (no additive needed) in the diff.

 

very cut and dry - C5 only use DEXRON 3, nothing else.

GM Dex3 part # 88861800
GM late iteration diff fluid (with friction mod already included) part #88862624
With the early version of diff fluid, 2oz can of fric mod part number is 88900330

To be honest, for the price and avaliability; i just went with Redline product.
Redline D4 ATF is Dex 3, $11.95 on Amazon.com and it is Prime elgible for 2nd day free shipping.
Redline 75W90 gear oil WITH ADDITIVE is $13.65 on Amazon.com as well

 

Keep in mind, the manufacturer wants your car to last through the warranty period. After that, they want to sell you another one....

 

The Corvette Central site goes into great detail to explain the various Dexron products, and mentions that GM has released a notice saying not to use Dexron IV (Dexron 4). But then they go on to say that the new(er) Dexron VI (Dexron 6) is their recommendation for both C5 and C6 transmissions.

You say GM also has issued a notice about not using Dexron 6 in the C5?

http://tech.corvettecentral.com/2011...d-performance/

Need to scroll way down to Transmission and Differential Servicing.....

 

Document ID# 1897292


Subject:Manual Transmission Fluid Usage In 2007 And Prior Manual Transmissions And Transfer Cases - keywords case fluid manual transmission transfer #PIP3836B - (02/05/2007)


Models:2007 and Prior Passenger Cars and Trucks
2007 and Prior HUMMER H2
2007 HUMMER H3
2007 and Prior Saturn Passenger Cars and Trucks


This PI is superseded to add a note under concerns. Please discard PIP3836A.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:

Use of manual transmission fluid part number 88861800 U.S. (88861801 Canada) in place of Dexron III.

Important Note: If the vehicle owners manual lists Dexron VI as the recommended transmission, transaxle or transfer case fluid disregard any information supplied in this PI. Use eSI and or the vehicle owners manual to determine what type of fluid should be used prior to referencing the below information

Recommendation/Instructions:

Manual Transmission fluid part number 88861800 U.S. (88861801 Canada) is currently available through GMSPO. Current and past model vehicles listed above with either a manual transmission or transfer case that REQUIRE Dexron III should use the above listed manual transmission fluid. This fluid is a direct replacement for Dexron III in manual transmissions and transfer cases. DO NOT use Dexron VI in place of the manual transmission fluid in any manual transmissions or transfer cases as a failure may result.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION


------------

Crystal clear, I would submit.

Note that the GM Manual Transmission Fluid is a Dex III. And per the C5 documentation Dex III is what the MN6 needs.

 

Conspiracy, wow. I don't know of a single case of a m6 crashing due to not changing fluid, there maybe some but i haven't read a single one on this forum and i read it every day for 1.5 yrs. I am done, out.

 

He is not saying that - he is merely stating the sales strategy employed by most automobile companies, which is, they want you to keep coming back for more, and not keep your car for ever. One reason they push leasing so hard.

Once the warranty is up, it's your problem - and your financial risk. So you choose how much risk to take on things like fluid changes, etc., etc. A lot of people on here have C5's with a lot of miles and a lot of years on them, so what you read is their experience - again, your call whether you follow their lead or not.

One interesting thing I have seen with a number of companies - normal commuting is now considered a "severe" operating environment, and many companies have shortened service intervals accordingly.

 

I agree! Thank you!

 

THANK YOU!!

 

You, sir, are more than welcome.

 

jackthelad, one more thank you for setting me on the correct path. Unbelievable the confusion about tranny fluid. It pays to be a skeptic about nearly every aspect of Corvette maintenance. Trust but Verify!

I visited with a mechanic at the local Chevy dealer today.... found this newer bulletin from GM that basically says the same thing (Do not use Dexron VI in manual transmissions.).

Also noticed that nowhere on the "New" GM manual transmission fluid bottle that replaces Dex III, does it say anything about Dex III. They apparently are trying hard to bury III.

http://www.revbase.com/BBBMotor/Tsb/...dPdf?id=168779