With the 300ZX convertible getting a full refresh this fall and winter, the transmission and differential were next on the list. Both still had their factory-original fluid from 1993 - 32 years in service. Christmas Eve seemed like as good a time as any to change that.
I started with the transmission. The drain plug is magnetic, and after pulling it the fluid came out looking about how you'd expect for three decades of service - dark, but not terrible.
The magnet on the plug looked normal - no concerning metal or shavings. That's a good sign for a transmission with only 38,900 miles on it. I refilled with Motul MT-90.
Next up was the rear differential. Same story - original fluid, same vintage. I drained it and refilled with Red Line 75W-90 GL-5+ Full Synthetic. I didn't grab any pictures of the diff work, but the process was straightforward.
Between the coolant flush, clutch fluid bleed, and now the transmission and diff, all the factory fluids in the drivetrain have been replaced. The only original fluid left in this car is probably whatever's still hiding in the power steering system. One less thing to worry about heading into the new year.
