mazzerman

Hi guys
just about to do an oil change on my 2005 6 speed manual, and i am reading 2 different things about correct oil.
1 is to use Dexron III and the other is to use 75w90 transmission fluid.
What are you guys using?
Cheers

schpenxel

Dextrin III ATF

I'm running redline D4 in mine and like it

mazzerman

I felt it might be that but its confusing for me to use Automatic transmission fluid in a manual gearbox, (im new to the Vette, only 2 weeks of ownership so still learning).

schpenxel

It's weird, but it is the right thing. It will also be on a sticker on the side of the transmission if memory serves

mazzerman

Thanks guys, thats what i will use for the change, i stuck to Mobile 1 for the engine oil change last week, so best to keep up with the recommendations.

torquetube

GM changed the name of what they used to sell as Dexron III to "Manual Transmission and Transfer Case Fluid", P/N 88861800. This I believe is the factory recommended fill for the manual gearbox.

There is a service bulletin warning against using Dexron IV as a substitute for Dexron III in this application.

For whatever it's worth, I have been using 88861800 in my T-56 for over 100K miles.

BlindSpot

Ditto. Don't mistake the upward compatible Dexron's as a substitute. Also, I can save you some time. Go to Amazon. They have it. Otherwise, you'll run around wasting time trying to find III in any stores today.

CMY SIX

I was taken aback when I heard of ATF in a Manual T, GM did it for fuel milage. I have no idea what tests they used? When I wanted to switch to ALL synthetic I started to look around. I found that BG oil products makes a specific 75/90w Full Syn gear lube to be used in trannys that are supposed to run atf, There's a WRX builder in Ohio that won't use anything but. Royal Purple makes a syncro-shift also, Ya know that noise inside the car that you think is "road noise" from the tires? it not! it's from the tranny. I put the BGproducts syncroshiftII in and I had to stop and check on the way home, it was so quite inside the car I thought there was something wrong! Gentleman it's time to rethink the ATF in a manual trans, with the new generation of synthetic oils, nothing has happend to my MPG

BlindSpot

I believe I read somewhere that the syncro clutch material is not compatible with Synthetic oils, thus the reason GM specified only Dex III, or at least the oil specced as 88861800 if it is, in fact Dex III repackaged. I've rebuilt older T-5s and the syncros are conical tapers with a clutch liner that absorbs oil and swells. Controlling how much/little these clutches swell determine gear engagement during cold shifting as well as clutch life. For some reasons beyond what I know, synthetic oils did not work.

mazzerman

this is the stuff i can readily get hold of, whats the opinion on this?
In the specs it does say "meets GM dexron III requirements"
theres a PDF spec sheet as well
https://www.wolfoil.com/en_com/Products/product_3010.aspx

BlindSpot

You're asking for an opinion which can be dangerous regarding the chemistry behind products like this. I've learned a while ago that "meets (or exceeds) the requirements of" statements can be a marketing effort more so than a precise product match.

I saw the same service bulletin that Torquetube mentions above regarding the incompatibility of Dexron VI in this manual teansmission, yet, it too states it meets the specifications of Dexron III. In that same service bulletin it clearly directed the field to use GM fluid #88861800. The spec sheet (or another one) references synthetic/semi-synthetic specs which I know I also saw as not meeting the testing requirements of the syncro clutch materials used in the 56 and the 6060.

So, I personally wouldn't use anything but 88861800, but anyone is free to go in any direction they wish. I am not qualified to predict what might or might not happen if you use this.

Regarding all fluids, gear oils, motor oils, coolant, brake fluids, When manufacturers conduct exhaustive engineering testing including destructive and life testing, why would one want stack up his/her intuition/opinion and deviate from the factory recommendation is confusing to me. Not you personally but anyone.

mazzerman

The problem i have is that here in Southern Spain there are no suppliers of GM oils anywhere so i have to look for an available brand that fulfills the requirements. I am thinking maybe the closest to GM in quality would be Mobil 1 ATF with the H rating.

BlindSpot

Oh, that makes it harder. Can you access Amazon? They have it. Don't know about int'l shipping of petroleum products.

mazzerman

Yeah i saw on Amazon.com they have it but as you say its shipping thats the problem, and a good price at $5.75
Its £57 on amazon UK
and not available on Amazon Spain
I cant even find a Chevy dealer in Spain, im waiting on an email from Chevy customer care to let me know if they have any servicing partners over here.

schpenxel

You can use Amsoil or Redline no problem. I have used both for 20K+ miles, no issues.

CMY SIX

I'm sure your right, I guess the CEO's of these Co's just like to go to court and fight lawsuits. I can see the board meetings now Hey Guys I want you to just make up some lube any so we can make $ on this sector of lubes don't worry about if the trannys fail just put anything in the bottles so we can sell it. you do know ALL the synthetic oil producers make some type of oil for this exact purpose, even GM offers a syn ATF for there trannys.. no friggin wonder I get banned all the time.

GOLD72

I have never ever read that. I have run over 100k accumulated miles with Redline D4 and AMSOIL ATF DEXRON-3 synthetic M6 tranny fluids in my 01Z, 06Z and ZR1 without issue.

BlindSpot

No problem, I understand your position. You're probably on to something. GM/Tremec must have missed it. You're right Syn oils have been around forever now. What were they thinking requiring Dex III.

I am not making recommendations to anyone just sharing some info. Nice thing is anyone can put whatever they want in their transmissions and it meets my expectations. I'll cheer you on!

MyLS1Hauls

The older T56 paper lined blocker rings definitely didn't like synthetic fluid...but those were never installed in a C6 T56. No issues with the bronze or carbon ones that are currently being used in T56/TR6060s.

schpenxel

I thought it was early C5 T56's that had the issue with synthetic fluids? Something about paper blocking rings. Not an issue on C6's.