Reply to "ZF oil cooler"

Mark, I've seen endurance race Panteras (3-6 hr events) with belt-driven pumps, having the drive pulley bolted to the back of the right halfshaft's inner u-joint. Racers usually do not trust electric pumps if a mechanically driven pump can be used. The GT-40 cooler was only about 4"x 6". Corvair engine oil coolers can be used.

Keep in mind that with lube temps below 200F, that's barely enough to boil out condensation moisture. Things don't get serious until you see above 240F, just as with engine oil temps. Most of us never see more than 180F and it took the ZF ovr 3 hrs sitting quietly to cool back down to room temp. My ZF temp sensor is in the side of the case very near the ring gear. You must remove the ZF from the car to do any drilling/tapping.

Synthetics can provide some extra temp protection w/no cooler. Note also that pumping honey-like 75W90 when cold is VERY difficult & tends to blow seals and use lots of power, so either a gravity system which is self-regulating, or some sort of manual on/off or a thermostatic valve and BIG lines would be a good idea. Air ducting to/from the cooler is important. Of course, complication & quite a few more failure points are also added.

On a GT-40, one team drilled the ZF's iron rear cover and pressed a seal in along with a short drive shaft pressed into the hollow mainshaft for a rear-mounted pump. You don't need a large pump- a very small one will move enough fluid to keep diff lube flowing. I suggest a 2-gear pump that's tolerant of debris & wear particles. I found a small aluminum military aircraft hydraulic pump that's about 2-1/2" square & only has 3/8" thick gears. I really think you're worrying about a non-problem in a 30 minute event.