Mishimoto MMTC-DMAX-06SL Trans Cooler for Duramax 6.6 LBZ/LMM 2006-10

2010 GMC Sierra 2500 6.6 with 6 speed Allison Definitely on of the biggest trans coolers on the market. Install was so simple it used existing holes and fit perfectly and is solid in its home. Will update when is run it for a while and see how it cools. I did do a trans fluid service with TranSynd and a PPE external filter. All in all took 2.5 gallons of fluid for service with larger cooler and filter.

Install took about 20min, took a hr round trip and seen a big difference in temperature. Highly recommend.

When hauling my 5th wheel trailer over the mountains with my 2007 Silverado Diesel, I would sometimes have overheated transmission oil, up around 300 degrees F. Normal driving temps with flat terrain would give me temps around 147 deg F. Since installing the cooler immediate resulted in cooler temps. Driving around town temps were 100-125 deg. F. The higest temp recorded over mountain passes between Seattle and Bryce Canyon in May was 147 degrees. This cooler is totally worth it. Good quality, easy fit and installment. Now the only gauge I monitor is the EGR, not worries any more about transmission temps.

This cooler fits nice and tight and seams really good quality. The issue is the factor power steering cooler mounts with a bolt right where this cooler has to go. I cut off the corner of the power steering cooler that would hit and used a rivet nut and moved the mounting bolt to the side. Fits great with a little work.

Easy to install, all fittings needed came nicely packaged. Haven't seen a drop in trans temps as others have, but it works.

Vehicle info: 2007.5 GMC 2500 with LMM duramax, with 35” tires. Install: very easy to install. Took about 45 minutes most of the time was spent trying to remove the grill because the clips would slip back in. Performance: The original trans cooler sat behind the facia and would receive air through the slit in the bumper. Now it sits behind grill in front of the radiator and AC condenser. The new location and larger cooler itself drastically lowered the transmission temp. This weekend while towing my 14k 5th wheel on flat ground with outside temp 85 degrees. Normally the transmission would run around 180-190, now the transmission ran around 150-170. Drove up the Cajon Pass again while towing my 5th wheel. Transmission temp would reach 230-240. Now it barely hit 200 degrees for a few seconds towards the top of the pass. Once I reached the top the transmission temp dropped faster than before. The new location didn’t affect AC performance nor engine temp. Truck seemed to perform better with it.

Very good quality. Helps trans temperatures stay low.

Dropped transmission temps majorly, towing toy hauler in 95 degree heat in mountains and never went 100 over ambient air, almost perfect but mine was missing the transmission hose and I had to source some 5/8 hydraulic line elsewhere because I needed in a hurry, I'm sure they would have taken care of it though. Very satisfying