ZF 10 (Hurth) Post Mortem

[Full Astern]

History: I bought this transmission new in 2006 and commissioned it in the Fall of 2007. It was attached to the back of my new Vetus M4.5 engine. The first oil change I did, after about 100 hours of light use produced quite dark oil. Not a good sign but perhaps once cleaned, things would be better. I flushed a quart of ATF, Dexron III as recommended, through it and re-filled with the proper volume. I then drained it after another 100 hours and found it darker than the first time.
After a trip from Maine to the Bahamas (about 750 hours from new) and then back to Florida, I lost confidence in it and bought a new ZF10. Vetus passed the buck to ZF dealers for warranty and mine essentially didn't qualify, a separate story.
Same issue with the new one only this one had a neutral rattle to boot! I now have over 800 hours on that one and I'm losing confidence in it so I thought I try rebuilding the first.
Here's what I found on disassembly:


It was not too hard to find the source:


My conclusion is that eather the casting for the housing was inadequately drilled for the blind capscrews (not deep enough) or the screws were too long. Either way, unless the unit was tampered with at the deler, the unit is clearly defective. (I didn't know this at the time and when I contacted Vetus about it, they referred me to ZF, who didn't want any part of it.

I don't know if this is an isolated case but I plan to examine some more corpses during the summer and will report here. I'll also answer any questions.
Tom

[Diesel Bill]

Kind of destroys your faith in quality control and manufacturers standing behind their products. It seems to be occurring every where.

[Ostinato]

I not sure why most(?) transmission manufacturers do not seem to want to build there products to the same standard as engine manufacturers in term of suravbility but that appears to be the case and ZF is clearly an example. I am now spending big dollars to dump my ZF SD10 sail drives in favor of Twin Disc SD60s. At least you can get a full manual on assembly and parts. ZF won't even supply that for their sail drive legs.

[Full Astern]

Originally Posted by Ostinato

I not sure why most(?) transmission manufacturers do not seem to want to build there products to the same standard as engine manufacturers in term of suravbility but that appears to be the case and ZF is clearly an example. I am now spending big dollars to dump my ZF SD10 sail drives in favor of Twin Disc SD60s. At least you can get a full manual on assembly and parts. ZF won't even supply that for their sail drive legs.

Exactly!
In my case, it would seem at last that there is nothing wrong with the design, just a mistake in the manufacturing process. And since that process is most likely very highly automated, it is unlikely that my case is unique. I will soon open another one of these with similar symptoms.
Full

[GordMay]

Greetings and welcome aboard the CF, Full.

[eceavchss]

You didn’t say which cap screws caused the issue. Are they the ones for the cover or the mounting cap screws?

[Full Astern]

Originally Posted by eceavchss

You didn’t say which cap screws caused the issue. Are they the ones for the cover or the mounting cap screws?

Good point. I just went to the shop to confirm and found that I had mistakenly assumed that they were the bearing plate bolts. Looking more carefully, I see that they are the bell housing plate bolts.
This transmission bolts from the inside of the bell housing into the transmission, requiring the removal of the bell housing to get the transmission off.
I guess that lets ZF off the hook puts the blame on Vetus. What's worse is that I think I used the same bolts on the new transmission. Glad you pointed that out. Apologies to ZF.
Full

[DeepFrz]

Just do a google custom search on the forum for ZF 10 and see what you get.

[chris95040]

Still, good info.