I have a 2000 t56 car. I’ve read about every thread under the sun. It’s been about 30k very hard miles since my tranny was filled by the shop that did my clutch install and I’d like to drain and change my tranny. The question is I’ve seen threads saying prior to 99 they were the cellulose blockers and then I’ve read 01-02 were the carbon ones. Whose right? Also, wtf fluid is best for a 2000 t56? I picked up 4 qts of pennzoil synchromesh (This kind) i see it replaces some of gm’s fills(12345349 or 12345577) but not 88861800..I’m so damn confused by all of these old threads people claiming this or that. If the synchromesh is not proper for me then I’ll take it back and order the GM 88861800 or whatever fluid is recommended..i couldn’t find any regular dex 3 on the shelf at the advance I stopped at

 

You're not really supposed to run Synchromesh. I have a 2000 as well and I run Redline D4 ATF in mine and I drive it hard, I have for about 25K miles and it still shifts great. When the temperature is in the 30's and 40's it'll be a bit notchy at first, but after you get some heat into it it drives great.

 

I just drained and refilled my T56 transmission and used the AC Delco I got at Amazon, expensive but I believe it is worth it, that is just me though. As far as best, this comes from the "source" and should be engineered to match the performance of the T56. The fluid in the manual, DexIII isn't made anymore in the "original formula" and was replaced by the 10-4033 (88861800). I searched for weeks and read many forums here and there are some fluids that are close to or "cover" DexIII but these are multi-purpose transmission fluids and I guess work great for newer transmissions, but the old school setup I am more comfortable with the recommended version. Odd how the factory originally recommended ATF for a manual transmission, at least this version states it is for manual transmissions. I don't know anything about the first question.

 

The cheapest dextron 3 has always worked for me and i used to drag race my car frequently.