Hurth ZF 10 M Transmission Problem - Any Advice on Removal ?

[DaveSIM]

DaveSIM I have had 2 of these ZF10M transmissions linked with a 43 HP Onan Diesel. The first box cracked the case after 10 yrs of use . The replacement started slipping like you mentioned in forward. I found a website where they recommended you flush the old trans fluid out put in Ford type F trans fluid and while tied at the dock run it in reverse and forward about 10 times About 15-20 minutes. Then flush it out and put in new Devcon II trans fluid. It worked for me and I did it again several yrs later and no slippage. After 2 more years I adjusted my maxi prop pitch to get a little more speed on the boat. Not a good idea as it failed in forward and I had to sail into my well rather hairy. I put in a ZF15M box to give a little more cushion on the capability after talking with ZF engineers. It has failed after 190 hours and it appears the pitch setting on the prop is the problem as the box was overheating, too much torque and not high enough engine revs. You have to set the pitch so that the engine can get to max revs when inthe water under full throttle. Mine did not. Currently I am looking at a new model or refurbing the old one.
It is no big problem to get the box out. 6 bolts on the bell housing and undoing the prop 4 bolts at the back and sliding the prop shaft back to get room to move the box back to get the spline out of the flywheel. Working upside down in a confined space is a good skill to have. I have done it 4 times now. I can give you more details if you wish and also ZF contacts. Good luck and let me know how it goes. DaveSIM 2/6/17