6 speed manual
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Cruising
Joined: Jun 2025
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From: Pennsylvania
6 speed manual
I need to change oil in my 99 6 speed trans. Any suggestions on oil to use since I hear dex3 is no longer available. I thought I read somewhere that I shouldn’t use synthetic. True or false ? Thanks in advance
Drifting
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Thread Starter
Cruising
Joined: Jun 2025
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From: Pennsylvania
Yes , I saw there were plenty of fluids that said they were compatible but also full synthetic. I cannot for the life of me remember where I was reading that synthetic’s should not be used in the early c5 tranny. Either way, I appreciate the answers given.
Melting Slicks
Joined: Sep 2021
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The non-synthetic recommendation was because supposedly the cellulose blocking rings either disintegrated or slipped too much due to the fluid being too slippery.
I don't know that I believe either claim but it's easy enough to find non-synthetic just in case there is something to the complaints.
I don't know that I believe either claim but it's easy enough to find non-synthetic just in case there is something to the complaints.
Drifting
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This may be what you were looking at as far as fluid recommendations, https://www.txdrivetrain.com/fluid-t...56-tr6060-faq/
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Cruising
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From: Pennsylvania
Thanks for the info. I believe that is what I had seen about the paper blocker rings in the tranny. There is conflicting information when you read about trans fluid. DexVI says backwards compatibile with all previous dex fluids, but , it is also synthetic. There are also other manufacturers that say compatible with Dex3 but as you read on they are also synthetic. So at this point I will use organic fluid just to be safe. Looks like Castrol makes an organic fluid ‘ Transmax Dex/Merc ‘ that I’ll try .
Melting Slicks
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I only bothered looking at information for one Amsoil product and it's synthetic and Dex III compatible.
https://www.amsoilcontent.com/ams/li...tins/g3110.pdf
"Use AMSOIL Signature Series Multi-Vehicle Synthetic ATF in
transmissions, hydraulics, power steering systems and other
APPLICATIONS THAT REQUIRE ANY OF THE FOLLOWING SPECIlCATIONS
Allison C-4, TES-389; BMW 7045E, 8072B, LA 2634, LT 71141; Chrysler ATF+4*, MOPAR*
ASRC, 68089195AA, 68049954AA; Ford MERCON*, MERCON* V, ESP-M2C166-H, FNR5,
M2C924-A, XL-12; GM DEXRON* II, DEXRON* III, AutoTrak II; Honda/Acura ATF-Z..."
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Drifting
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From: Lakeland, Florida
Instructor
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Went through the same process not long ago with my 2000. GM 88861800 also labeled as ACDelco 10-4033 is the recommended trans fluid for the 97-00 Corvettes with the T56.
Last edited by Midwest19942000; Jul 9, 2025 at 10:58 PM.
Racer
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From: Detroit area, Michigan
Browse this thread:
Transmission Fluid - Manual
https://www.corvetteforum.com/forums...id-manual.html
I just purchased Mobile ATF D/M from Rock Auto for a good price.
Transmission Fluid - Manual
https://www.corvetteforum.com/forums...id-manual.html
I just purchased Mobile ATF D/M from Rock Auto for a good price.
Instructor
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From: Thunder Bay
2025 C5 of the Year Finalist - Unmodified
2024 C5 of the Year Finalist - Unmodified
I went through this fairly recently too. I have an '03 so it might not be a thing, but the manual and tag still says Dex III.
Penzoil (and Mobil 1) sell "Automatic Transmission Fluid" that'll work. Just read the label, look for Dex III compatible and non-synthetic
Penzoil (and Mobil 1) sell "Automatic Transmission Fluid" that'll work. Just read the label, look for Dex III compatible and non-synthetic
Safety Car
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No Hostility Be Happy
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From: South Hill Wa
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Tuning in for this one. Pretty sure the fluid in my 97 is original. It only has 46k miles on it but original none the less.
Even though I don't believe it it recommended for the application I am tempted to try Pennzoil Syncromesh.
I've used it in other T56s with amazing results. I've also used it in ZF6s, Tremec 3650s and T5s.
Even though I don't believe it it recommended for the application I am tempted to try Pennzoil Syncromesh.
I've used it in other T56s with amazing results. I've also used it in ZF6s, Tremec 3650s and T5s.
No Hostility Be Happy
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From: South Hill Wa
2022 C5 of the Year Finalist - Modified
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Alright, I'm learning **** already I didn't want to lol. I coulda swore Syncromesh was NOT synthetic but turns out that it is.
More reading.
More reading.
No Hostility Be Happy
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From: South Hill Wa
2022 C5 of the Year Finalist - Modified
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Thread Starter
Cruising
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From: Pennsylvania
So …. I have been digging deeper into the fluids for the pre 2000 6 speed & seems just about all the fluids are synthetic now & a lot of them say they are compatible with Dexron 3 , which I don’t doubt that the fluids themselves ARE compatible with each other , but my real issue is that they are not compatible with the pre 2000 tranny. I just have to change the angle I’m looking at this from. Thanks for all the input from everyone
Drifting
Joined: Sep 2022
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So …. I have been digging deeper into the fluids for the pre 2000 6 speed & seems just about all the fluids are synthetic now & a lot of them say they are compatible with Dexron 3 , which I don’t doubt that the fluids themselves ARE compatible with each other , but my real issue is that they are not compatible with the pre 2000 tranny. I just have to change the angle I’m looking at this from. Thanks for all the input from everyone
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