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Discussion Starter #1
Hi, I'm at 5K miles and going to get my transmission fluid changed today on my M6. A few questions:

(1) the manual calls for DEXRON III automatic fluid approved for "H" specifications. Should I stick with this or consider synthetic? If I went synthetic would that loosen up the shifting? What are the pros & cons.

(2) Do I just get a drain and fill or is there a filter change associated with this service. I saw a few posts in the archives mentioning transmission filter.

Thanks in advance. The tranny changes are new to me as my last car had a sealed tranny that never needed service.
 

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I'd like to know about the synthetic as well. I've heard that it's actually too slippery and it plays havoc with the syncros because they need a certain amount of friction to work.

Is this true or just BS.
 

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Dexron III is a specification. There are many synthetic fluids on the market that meet GM Dexron III requirements and will not invalidate your warranty.

My Z06 has the same gearbox as the GTO and I've been using AMSOIL ATF (a synthetic fluid which meets Dexron III standards) on the track for years without a problem. Synthetics will hold up to the heat generated in our gearboxes much better than a non-synthetic.

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:cheers
 

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Russ2005 said:
Hi, I'm at 5K miles and going to get my transmission fluid changed today on my M6. A few questions:

(1) the manual calls for DEXRON III automatic fluid approved for "H" specifications. Should I stick with this or consider synthetic? If I went synthetic would that loosen up the shifting? What are the pros & cons.

(2) Do I just get a drain and fill or is there a filter change associated with this service. I saw a few posts in the archives mentioning transmission filter.

Thanks in advance. The tranny changes are new to me as my last car had a sealed tranny that never needed service.
Russ,
Answered the Dexron III question above. All of my customers have reported an improved shift feel when going to AMSOIL ATF. The pro's are:
Improves fuel efficiency, reduces transmission temperatures and increases transmission life. Provides unsurpassed thermal stability and up to five times the service life of conventional ATFs. Delivers maximum protection for towing and other severe-duty applications.
The only con in my opinion may be a slightly higher cost than non-synthetic.

Manual tranny is just a drain and fill. Automatic transmission has a filter and may require a flush to get all the old fluid out. For my Z06 manual, I just open the fill plug, open the drain plug, replace the drain plug when the fluid stops coming out, pump fluid into the tranny, replace the fill plug.

Note: The API has not defined the term "synthetic". There are three different types of synthetics on the market, Group III is the cheapest and uses a highly refined petroleum basestock, Group IV uses a man made PAO basestock, Group V uses esters and other's that don't fit into Group III and IV. Most synthetics on the market are Group III. If the company doesn't tell you what there base stock is, it is probably a Group III synthetic. AMSOIL and Mobil 1 use PAO basestocks. :cheers
 

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Discussion Starter #5
Thanks for the info all.

I checked with my racing buddy and he said the same thing as subdriver regarding the synthetic. However, he also runs a repair shop and told me that GM will void the warranty if you use anything other than the GM fluid and have a transmission problem (is that true GoatGirl and GTO Dealer?). He knew this from direct experience with his 'vettes at his local dealer. He told me that GM's Dexron III is very good fluid and that there is no reason not to continue to use that.

Local GM dealer parts shop said "absolutely not on a synthetic, do not use anything other than Dexron III which is specified" quote-unquote. He told me the Dexron is not a synthetic.

I went to buy the Dexron III and the same guy told me they don't make that any more and Dexron IV is the replacement (can anyone confirm that?). It was marked with the H specification, so I bought it for $4.28/quart. The ****ass could not tell me how many quarts the tranny took and sold me 4 saying there is no way it takes more than that. Guess what, it takes 4.6 quarts.

Thanks for the assistance.
 

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You absolutely don't want to use synthetic ATF in automatic GM transmissions. You will love the way the transmission feels when you shift it after filling with a good synthetic (AmsOil, Mobile 1, Royal Purple Syncromax, or RedLine). These are approved ATF fluids and won't put you out of a warrantee (GTO dealers can counter but that is from prior board discussion).

The trick with the M6 on the GTOs is it is installed at a different angle than other GM M6 applications and the plug labeled "fill" on the driver's side will only get in 4.0 quarts vs the 4.6 it needs (someone yell if my memory is wrong on the volumes). If you follow the directions to use the back-up switch plug on the passenger's side, beware that you can over fill it big time because you don't fill until it leaks out, you fill 4.6 quarts only. The other unorthodox alternative is to jack your car up on the driver's side (use jack stands for safety) and then fill through the "fill" plug. With the tilt you can get in the correct amount.

If you fill only 4 quarts, one of the bearings is not getting enough oil. If you over-fill, you run the risk of blowing a seal, etc.
 

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I drained my M6 and it shifts smoother with a little less effort. The difference is more noticable in cold weather. The factory service manual is inaccurate because it says fill through the backup switch port until oil reaches the backup switch port level...that is wrong! way to much oil! The manual also says 4.6 qts...that is correct. I bought a handy little fluid pump from PEP Boys, makes the job clean and simple. Enjoy the synthetic ATF you will feel the difference :cheers
 

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All of your fluid specs are in the owners manual. I am an ASE certified mechanic and I used royal purple synthetic dextron III and told the dealer about it when they were doing trans work on it and they didn't void my warranty. You can use any dex III you want to as long as it's dex III. I also changed my diff fluid to royal purple. I had 6000 miles on my goat when I changed the fluids. They were both black and burnt as they could be. If you are driving it hard, I would suggest changing the fluid often. If it loses viscosity, you could have serious wear issues and shorten the life of the trans and differential. There is no filter in manual transmissions, but you will need some kind of hand pump to put the fluid in the trans because the drain hole is too high to get enough tilt to pour it in. They sell hand pumps that screw on the bottle at parts stores. If you change the differential fluid, make sure that the fluid you buy has limited slip additive in it to keep it from foaming or the limited slip won't function properly and the fluid will get very foamy. If it doesn't have the additive, you can buy a small bottle of additive from the parts store. If you have any questions, feel free to email me at [email protected]. Be sure to put something in the subject line so I don't delete it as spam.
:D
 

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Discussion Starter #9
QSGTO. I went to localy GM dealer and the parts guy said DEX III is not made any more. Also, he said DEX III is not a synthetic. They sold me DEX IV. Do you know anything about that?
 

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Russ2005 said:
QSGTO. I went to localy GM dealer and the parts guy said DEX III is not made any more. Also, he said DEX III is not a synthetic. They sold me DEX IV. Do you know anything about that?
GM may not sell DEX III anymore, but it can be bought at any parts store. We buy it by the 55 gallon drum. Dex IV will cover from IV down to the earliest. It is not synthetic, but royal purple makes MAX ATF which is synthetic and will work in DEX III applications.
 

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Russ2005 said:
Local GM dealer parts shop said "absolutely not on a synthetic, do not use anything other than Dexron III which is specified" quote-unquote.
Sounds like a guy trying to make you buy his fluid. The Magnuson-Moss Act makes it illegal for any manufacturer to tie warranty provisions to use of a specific fluid unless they provide you the fluid or they have a waiver on file. Thus the auto manufacturers list specifications for the replacement fluid, not an actual fluid. Any fluid, synthetic or non-synthetic, meeting GM Dexron III standards will absolutely not invalidate your warranty.

And yes, the factory fluid is not synthetic, so in my humble opinion, any synthetic you use will be a vast step up.

GM is learning this lesson and they have recently come out with a new fluid, Dexron VI. From what I've read, to meet the new Dexron VI standard, a fluid will have to be either at least a Group III synthetic, or possibly a Group II/III blend. To the best of my knowledge, no aftermarket company has come out with a fluid meeting the new Dexron VI standard yet. Since AMSOIL uses a Group IV synthetic base stock, I'm sure they'll have no problem meeting the new standard, they just have to formulate one to the proper viscosity requirements of the new fluid. :cheers
 

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Fluid specs in the '06 owners manual

I just checked my '06 Owners Manual.

For the automatic transmission, it specifies: Dexron-VI Automatic Transmission Fluid.

For the manual transmission, it specifies: Dexron-III Automatic Transmission Fluid. Look for "Approved for the H-Specification" on the label. (The same exact wording is also specified for the power steering system)

I have a six-speed, so I assume III-H is all that is necessary for mine.

This was in the PDF manual downloaded from mygmlink.com, not the paper manual as that is out in the glove box.
 
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