Sigi_H

That's plausible, but the OD was rebuilt 12,000 km ago. That's why I don't really believe it yet. Because there is often too little oil in the OD, it normally doesn't engage. The behaviour not to disengage is only possible with gear oil in it. That's why I really want to measure the pressure in order to see a pressure profile and see the reason for shifting or not shifting. I built a provisional catch tank from a PET bottle, to see if oil is coming from the breather.

You are absolutely right. This was just a test, to learn more about the hydraulic pressure. Results point to the necessity of measuring the pressure. Even it was absolutely the wrong oil (it is too slippery) there was no slipping. The fact, that it did not disengage reliably may point to the solenoid valve, which got stuck with the high viscosity.

Hi all, I am the one who was writing the article at landypedia mentioned above. https://www.landypedia.de/index.php/Überholung_eines_GKN_Overdrives It was a hard peace of work reading all that stuff, but worth every line. Since I am not a specialist with GKN ODs, I do have problems with mine as well 🙂 My suggestion (and I am about that) is to measure the hydraulic pressure of the OD. In my eyes, it can be made at the screw, which sits beside the plate on the bottom. I think the hole will just go into the oil chanel of the solenoid. My experience with mine is, that it will disengage when it becomes hot. I made some experiments with oils. With ATF it disengages after about 25 km. Half ATF and half engine oil extend it up to 40 km. Only engine oil will make 50 km. Now I tried 75W90 gearbox oil ... and found it engaging quite reliable and long ... but it did not disengage anymore. Only if revs are really down. It seems to be very dependent on viscosity. Another problem seems to be disappearing oil. I put the vent hose into a catch tank, to see if it disappears here. I did not check yet, if it disappears into the LT230. I heard about it, but don't think so. Sigi