ZF transmission

Paul Osterberg

How often should one change the oil in the ZF Transmission? assume just pump out the old oil and fill new , how much oil is it in the transmission? ATF is that the same as 90w Gear oil?

Paul on SY Kerpa SM#259


Dean Gillies

I’ve just fitted a new one, and the numbers I’ve been given are:
25hours after installation, then every 300hours or 12 monthly after that.

ATF (Automatic Transmission Fluid), is not 80W.
It is a specific product for automatic transmissions (it’s invariably red in colour).
There is a very long list of compatible ATF products in the ZF25 operating manual.
Others may have favourite brands, but you can use pretty much any fluid designated ATF for a modern vehicle auto transmission.
Any gas station will sell it.

Your ZF-25 takes 3 Litres, plus a bit more for the cooler, brake and lines.


AMEL 54#154

Dean Gillies

Oh, and you do not need a pump.
There is a convenient drain plug near the lower stbd fwd corner of the box.
(Easily accessible on the 54)

The most difficult part of the job is not making a mess!



I think I remember that you have the Volvo TMD22 engine.  If so, this applies to you...

You have to be a very careful talking about the ZF transmissions.  The ZF25M transmission that came on the Volvo TMD22 is a manual shift transmission, and holds about 0.75 liters of DEXTRAN IV automatic transmission fluid, NOT 90 weight oil.  The same exact machine was called an HBW250 before ZF and Hurth joined forces.

Other engines used a ZF25 transmission, which is a hydraulic shifting model with larger horsepower capacity and a completely different design.  It causes no end of confusion with model numbers so similar and actual designs so different!

The recommendation for change interval in my manual for the ZF25M is "Once a year." There is no change interval recommended based on hours of operation.  

Bill Kinney
SM160, Harmonie
Annapolis, MD, USA

Paul Osterberg

Bill Thank you, you remember right. W have had the boat for 3,5 years and 1500 h on the engine, probably time to change the transmission oil.
Paul SY Kerpa SM#259