How To: Choose the Correct Transmission Fluid

Transmission Fluid TREMEC TKO MAGNUM T5 A41One of the most popular questions we get is “What fluid should I use in my new transmission?”

The question has 3 answers….First, if the transmission has not been driven yet, you should follow the proper break-in procedure.

That is 500-600 miles of light-duty driving (no hard starts, no burnouts, no racing) and the fluid to use is regular old garden-variety DexronIII/Mercon automatic transmission fluid. This is a very thin viscosity fluid that has excellent cleaning properties as well as the proper friction modifiers for use with the blocker rings and synchronizers found in the TKO.

Once you have completed the break-in, you can drain and dispose of the used fluid, then refill with fresh fluid. The one to use is called Synchromesh.  You can find this is several places; the easiest is to head over to your local GM dealer and purchase it there. The part number is 88900333 (formerly 12345349) or you can go to your local auto parts store (Advance Auto Parts, O’Reilly’s, Auto Zone) and ask for Pennzoil 3501.

Once the break in and final fill are complete, you can sit back and enjoy your ride for the next 30,000 miles!!!

If you are one of those that insist on synthetic fluid in your transmission, we have approved the Mobil1 ATF – Multi Vehicle formula for use in the TKO 5 speed transmissions. This is the ONLY synthetic fluid that we authorize. Using Royal Purple, Amsoil, or the like will likely cause hard shifting, and possibly overheating of the transmission. The friction modifiers used in those brands of synthetic fluid typically do not react well to the blocker rings and synchronizers.

For the T56 aficionados out there, the fluid requirements for the T56 Magnum are even easier. We suggest that you use Dexron III/ Mercon ONLY, and not to use a synthetic in those transmissions. As with the TKO, we do not advocate the use of any fluid additives.

If you are the proud owner of one of our A41 4-speed overdrive automatic transmissions, we only authorize one fluid for use in those. That is the Mobil1 ATF-Multi Vehicle Formula. Mobil1 is the fluid that is shipped with your A41 automatic transmission when you buy from Silver Sport Transmissions.

This synthetic fluid has the anti-foaming additives necessary for long transmission life, as well as lubricating properties for lower operating temperature and longer band and converter life.