Transmission failure

[dhagen]

I changed the transmission fluid on my 2001 C34 MkII last fall for the first time.  Until then, it shifted fine.  Then, I had trouble shifting from reverse to forward.  It would take a few seconds before it shifted.  If I advanced the throttle slightly, it would go into gear.  Thursday, I was coming into the slip and the guy next to me backed out in front of me, so I had to quickly shift into reverse and heard a clunk., but the boat went into reverse and then into forward when I shifted back into forward.  Yesterday, we took the boat out, again having a slight  hesitation in going from reverse to forward.  Then, as we were motoring just outside of the marina at about 1800 RPM, there was a clunk and I lost forward and reverse and we had to be towed back in.  The cable is still connected to the transmission, and the lever at the transmission moves fore and aft, but nothing happens at the prop shaft.  Is it possible that the shift lever at the transmission is loose on the shaft into the transmission?  I couldn't tell yesterday.  Or do I have to replace the transmission, or is there something else that is wrong? Any help would be much appreciated. By the way, the shift lever has always hit the pedestal when shifting into forward, but no trouble in the 12 years I've owned it until now.

[Roc]

When you check the level of the fluid you are not supposed to thread the dipstick all the way down. You just rest it on top without screwing it in. If you checked the level  by totally screwing in the dipstick you may have under filled the fluid. Since you say this is the first time you changed it my thought is you may have checked the level this way.

[dhagen]

No, I did not screw in the dipstick when checking the level. If anything, there is slightly more fluid than required. I checked it again after I had the problem yesterday.

[KWKloeber]

Yes, It's possible that the shifter arm is slipping on its shaft. That would be the best of situations.
20 ft-lbs is the spec on the tension bolt.

[scgunner]

dhagen,

Whenever I have a problem I always start with the easy fix first and hope for the best. In this case I'd start with the shift linkage. I'd disconnect the remote shifter at the trans and see if I could shift it at the trans itself. This can be done in the slip, you should be able to see(prop shaft) and feel if the trans will go into forward and reverse. If it still won't shift properly you're probably going to have to pull the trans.

[Colonel Butler]

With respect to the comment about the shift lever hitting the binnacle... Check which hole on the gearbox shift arm the shift cable is attached to. I had to move mine to the inner radius one to ensure the gearbox shift arm was moving its full range to ensure proper engagement of forward gear. Incomplete engagement could cause undue wear.

I had my transmission out to replace the damper plate this winter. Not too bad of a job.

[dhagen]

I checked the shift arm at the transmission.  When I move it, the shaft turns, so unfortunately, that is not the problem.  I will have to remove the transmission.  Any idea how long of a job that is?  I'm going to have the marina do it, but want to have some idea how long it should take.  I'm assuming that the front of the wood access box can be disassembled with removal of just a few screws Thanks.

[dhagen]

FYI, it is an M35B universal diesel with a ZF 10M/Hurth 100 transmission.

[Ron Hill]

dhag : You should be able to remove the transmission in no more that 2 hours. I'll guess it should be even less than 1 hour.  Just a few bolts!!

A thought

[Noah]

With due respect, (and not being a mechanic), I suspect Ron's timeframe is overly optimistic and assumes none of the bolts to the coupler, etc. are frozen, and there is nothing else in the way that must be removed such as the heat exchanger, shifting linkage brackets, etc.—and all your stars are aligned.

[dhagen]

Yeah, to me it looks like more than an hour.  There are a few things in the way that will have to be moved to get at it.  But if it is more than 4 hours, I can question why it took so long. Thanks.

[Noah]

Also, remember when calculating this will be a "roundtrip" journey and all will have to be reassembled too. Also maybe involve filling burping coolant if HX is removed. It can help by soaking the coupler bolts/nuts with penetrating oil ahead of time. However, be very careful not to get any oil on the rear transmission seal as I hear it will eat it up. Use a Q-tip to apply. Maybe not an issue if tranny needs rebuilding?

[Ron Hill]

Noah : I had to change out a faulty transmission on an a new M25XPB engine (which is the same as ZF10 as a M35BC). There were 2 of us, but as you know only one person can get down in the aft cabin behind the engine to do the work!
 
I still believe that it only took about an hour - however it was a new engine and all attachments were only a week or so old!   

A few thoughts

[dhagen]

Marine Parts Source in MI has a new replacement transmission by Baysan Marine that he says is a direct replacement. It is 1/2"-3/4" longer so it would push the prop back that much. Would that be a problem? I think I have that much room at the rudder.

[Jon W]

You gotta love suppliers. It's a direct replacement, except it's a little bit different.