retiredff

The Amsoil Torque Drive is only available in Gal. or larger, I ordered a Gal. so I'll be fine.

Thanks Bill.

jackthelad

No need to use anything other than a mineral oil that meets the old GM Dex III.

One interesting aside, at about 65k, I was getting unexplained grinding occasionally on shifts, and 1-2 was very balky. I thought, this is gonna be expensive, but first I drained the oil to take a look at it. Rather less than 3 quarts came out - no signs of debris, though. Evaporation, low factory fill, who knows? Certainly no leaks. Anyway I filled with Valvoline Dex/Merc which meets the old DEX III spec, and I am now back to non balking, smooth and quick shifts. I won't realy on the GM "for life" recommendation again, tho'.

As an aside, I also have a stick shift K1500 with calls for a particular GM spec Synchro fluid (NOT the same as the current GM recommendation for the C5 MN6). It has the GM-Chrysler New Venture tranny, BTW. Anyway, the synchromesh was slow and easily beaten, so I tried the Royal Purple synthetic "equivalent" - and it made absolutely zip difference. Felt exactly the same, still crunched if you shifted anywhere near quickly. So, I am on Plan B - shift gently. And don't expect miracles from a change in brand of tranny fluid.

nitromainia

Antique Thead Resurrection!

At 60,000 miles and 20 years...

I’m contemplating a First Change of of what is likely the factory DexIII fill on the MN6 in a 2004

So, ...with Millions of Miles of “Consensus”

What is the current thinking ?? Track guys that have Experience ?





Stirring the Hornets Nest for Opinion

Dads2kconvertible

Mobil 1 has a tool on their website, I'd start there for factual information.
For a 2004 they show

carry265

I wouldn't recommend using Mobil 1 Synthetic ATF in a 6-speed car. It's generally not recommended to use automatic transmission fluid (ATF) in manual transmission gearboxes. Instead, I would suggest using a manual transmission fluid that is specifically formulated for your car's transmission.

captain vette

ATF is exactly what GM recommends in the T56 trans although not synthetic

Prop Joe

I posted this in another thread...
I have a 98' with the "Paper blocker rings" I did hours and hours of research. In the end I went with the current GM/AC Delco Manual gearbox flavor. PN 88861800. Its a mineral based fluid. The Summit search engine does not list the C5 specifically, but does list this for all Tremec trans used in Corvettes C6 and C7 including the ZR1. In the comments section a couple C5 owners reported in using this fluid as well.
https://www.summitracing.com/parts/ADO-10-4033
GM Tech link on the subject:
https://web.archive.org/web/20140617...hlink/2009/05/
"TIP: Any vehicle that previously used DEXRON-III for a manual transmission or transfer case should now use p/n 88861800 (88861801 in Canada) Manual Transmission and Transfer Case Fluid."
Another tip:
"All licenses for DEXRON-III expired at the end of 2006 and will not be renewed. Fluids sold in the market after that date bearing claims such as "suitable for use in DEXRON-III applications" or similar wording should be avoided, because 'DEXRON-III' fluids are no longer checked and policed by GM and therefore may not be the originally tested and approved formulation."
YMMV
Edit: one of the 1st things I did to my car was the TMod shifter box. I really like it and then added the reduced throw shifter later. I like the shifter they make but the rebuilt lower (or new CNC) box is really nice. Add whatever shifter you like or even the stock one and I think you'll like the results of the TMod lower
https://tmodcustoms.com/products/upgraded-factory-boxes