the aux fan is actually mounted to the engine oil cooler, the tranny cooler is lower, longer, and more rectangular in shape, very hard to put a fan on it at all, unless you replace it with a new one or re-mount it. since installing the 3.15 t-case gears and the 4.90 R&P gears, never overheats even in the hottest of Arizona heat. I used a small flex a lite fan, the smallest one they make, fits nicely in there, only put it b/c it fits and thought that between that small fan the AC condensor fan, it would help if it really got hot.

generally speaking, fans do help, but I will tell you, that the mechanical water pump in the montero does not push much coolant when idling or at very low rpms. so depsite how good your radiator or cooling fans are, if the coolant isn't flowing fast enough due to low rpms, it won't matter much, i usually throw it in neutral, and rev to about 3500 rpms, cools it down in just a few short minutes, but like I said, with the new gears, the temp gauge never goes above halfway.