Tranny smoking, then slipping - diagnosis process?

[Pub911]

Yep, last sail of the season, we barely made it up the Housatonic to Shelton CT due to some sort of tranny issue. First smoke...smelled like a belt buring, or burt oil, tough to tell. The dipstick in the Hurth HBW50 appeared dry - can't remember the last time I check it (yikes!). We added the right ATF fluid and were able to limp at low revs (e.g. 2,000) but only at about 1.5 Kts thru the water. Reverse seemed to have full power, but my boat is impossible to steer in a straight line in reverse.

Well, long story short, 2 nerve-wracking bridge openings, 3 emergency achor deployments and 7 hours after we left New Haven, we got there.

If it matters, this is a 15 year old tranny in a 36 year old NorthStar 38, 16,000lb sloop rig with a 2-blade prop, fin keel and a clean bottom. The engine is also 15 years old - a Universal M4-30 (25 hp 4 cyl diesel.)

Now...
Is it the tranny? or the damper plates? any suggestions on the path of least resistance and cost to diagnose and fix?

Thanks all!!!

[captbillc]

PUB 911------ the plates in the gear for forward are probably burned & warped. the tranny will have to be removed & overhauled. i don't know what it would cost, since i haven't taken a hurth apart. i am quite sure it is on the same design as kanzaki's on the yanmars which i have overhauled.

[Pub911]

Thanks, Captbillc.

So I guess I'm in for cost on both. The rebuild on the tranny is likely more expensive of the two - web research suggests I can get a rebuilt for as low as $700. Any way of knowing for sure that I need to spend that (shy of doing the plates, waiting till Spring, and trying it out)?

Is there a bench test I can do on the tranny or are there tell-tale signs of need for rebuild? Other than the above-mentioned symptoms that is - or are those symptoms proof enough?

Much obliged for assisting in my hopeful frugality.

thx!

[Rockter]

But it probably won't be just the plates that have gotten hurt. I suspect the lack of fluid will have threatened the entire 'box.

Only a full strip will betray it.

My own 'box failed the final drive seal and dripped dry, and I didn't know for how long. It always held oil up until then. I seemed to have gotten away with it, 10 years on.

Now it's gearbox dip, every trip.

[Pub911]

Thank you both!!!

[rocinante33]

My HBW50 slipped (without the burning smell or lack of fluid). I read about other horror stories about rebuilds & decided to replace it. You can get a replacement for about $1100. I got mine (a ZF10 which is the next bigger model) from MER marine in Seattle.

[Rockter]

As I did, it is easy to get lulled into a sense of security. If your gearbox never seems to lose oil, you don't check the oil level as often, or at all.
My first warning was "it sounds a bit clunky, doesn't it?".
The dipstick betrayed that there was no oil in it.

[Pub911]

Rocinante, is the ZF10 a straight up 1-for-1 replacement with no adjustments needed to make it fit?