Project Tundra, Keep the Transmission Cool with B&M

We refilled the transmission with Redline D6 ATF.  Redline D6 is a low viscosity synthetic ATF with minimal viscous drag.  It meets and exceeds Toyota’s WS ATF standard.  D6 has superior thermal stability, maintains viscosity levels, and features lower oxidation and volatility while providing the required frictional characteristics of Toyota spec fluid.

Red Line’s full-synthetic D6 ATF has a low viscosity compared to other AFT fluids and is designed for better fuel efficiency and less power loss in CAFE testing.  Despite being thin, Redline D6 exceeds the latest Dextron VI viscosity stability standard. Dexron VI requires a different approach to a conventional ATF formulation. Rather than beginning with a 7.5 cSt fluid and allowing a viscosity loss in use to drop to 5.5 cSt, the Dexron VI fluid requires a starting viscosity of less than 6.4 and a final drop to no less than 5.5 cSt. Red Line D6 will drop to no less than 6.1 cSt. Since the final viscosity after use of these fluids are similar, Dexron VI fluids can be used where Dexron III fluids were previously recommended.

D6 ATF also provides significantly improved gear protection and will provide a GL-4 level of gear protection. D6’s balanced frictional characteristics provide smooth and consistent shifts over extended drain intervals. D6’s superior stability compared to petroleum ATFs allows high-temperature operation without varnishing valves and clutches which leads to transmission failure.

Steve and Howard fill the transmission using a gear oil pump to pump the Redline D6 into the pan.  The Toyota transmission doesn’t have a dipstick so you cant use a funnel on it like most other transmissions.  You have to add fluid through a fill port until it comes out of the hole at the top of the pan’s level check tower, which is in the middle of the pan.

The car had to be started, moved through all the gear positions and warmed up fully.  The oil level had to be checked and more oil added.  This had to be repeated about 3x before the transmission fluid level was truly full and the level repeatable.

For those of you that off-road, the B&M transmission pan does not hang below the cross members or frame rails. So it’s not the lowest part of the undercarriage.  It should not interfere with underbody skid plates or armor either.

After filling the transmission we were ready to hit the road.  The first thing we noticed was smoother and faster shifting, due to the Redline D6 fluid. Over extended driving, we noticed that the transmission ran much cooler. Before the pan, our gauge used to go about 5/8’s of the way up in normal driving and now it was steady at 3/8 of the way up.


    1. An automatic transmission is a little different than an engine, the valve body is extremely sensitive to dirt and the fluid is prone to metallic and friction material contamination. Because of this, pans have the oil pickups higher than an engine and usually have magnets in the bottom. The idea is for debris to stay in the bottom of the pan.

Leave a Reply

Your email address will not be published. Required fields are marked *