Hi all, I keep reading conflicting info on how much oil I need to do a change, likely as there’s a few different ways to do it. Most kits come with 7 litres which they say is enough to do a “double flush” which to me means emptying, filling, running the car, emptying and filling again.

others have said 7 litres isn’t enough to do this, or that I could empty, run the car for 30 secs to pump everything out the oil cooler, then refill.

Grateful for any experiences. Thanks.

 

I have been done oilchange for ZF 6HP and 8HP trannys maybe 10-15 times, and dropping the oil/pan and filling up again by correct process descripted on ZF instructions take about 6 liters of oil. (+/- 0.3 l)
You need min 13 liters to do it twise. Doing twise in row is only needed if the box haven´t seen new oil for looong period. Naturally then you like to change the pan(filter) twise as well.
I would drive a some days, maybe a week, between changes to let new filter collect as much friction clutch plates particles from oil as possible before second change.

 

thanks, I should have said it’s the 6hp and it’s 11 years old, 95k and never had it changed. Do you think two changes are warranted please?

does the ZF procedure involve starting the engine to pump it out the cooler? All videos and write ups I’ve seen don’t do this and just do a simple drain and are only putting in around 4 litres before it’s full again. Even when warmed and topped up.

thanks again.

 

For 65k miles i would just prepare for one change and check the condition of oil coming out. If its smels burnt instead just normal bad, i would do second change.
No flushing needed or empty the turbine/cooler by running engine. (running engine without oil inside can damage the oil pump or bearings)
If you purchase ZF 6HP service kit, with oils, pan and screws, it include a good instruction booklet. Or you can watch how to do it from ZF service channel:
I highly recommend the ZF HP6 28 service kit with correct oils. (Lifeguard 6 for 6HP) Its reasonable price, available almost any good parts shop because same tranny are used in Land Rovers, BMW:s, Audis, VW:s, KIA/Hyundai, Ford, Porsche, Aston, GM, Bentley, Maserati ...

 

I always bleed out the fluid through the oil cooler hoses until it runs clean. It's so satisfying to know you aren't leaving any of the old and dirty fluid behind.

For the bleed, I drain the pan through the drain plug, replace the pan/filter, fill it up to the top of the fill plug, remove the return line from the cooler and put an extension hose into an empty gallon plastic jug, run the engine until the jug fills up half way with fluid, and repeat until the fluid runs clean. Then I follow the normal procedure for setting the level. Never had any trouble with any of my several ZF transmission, or any other make of transmission, doing this method.