[ttyR2]

Two questions. does the oil pump in the ZF-6 spin whenever the clutch is engaged even with the transmission in neutral? Which one of the two oil pipes on the transmission is the return line?

I'm changing out the transmission fluid in my truck and want to flush the cooler and cooler lines at the same time.

 

[txgp17]

Two questions. does the oil pump in the ZF-6 spin whenever the clutch is engaged even with the transmission in neutral?

To the best of my knowledge, yes. The oil pump is located on the input side of the transmission. If it were on the output side, it would run very slow in 1st gear, and very very fast in 5th. What's worse, it would run backwards in reverse.

Which one of the two oil pipes on the transmission is the return line?

Good question. You could disconnect one, and crank it up, then let the clutch out for a second, then shut it off. The fluid path should be obvious then.