Rattling in transmission when I put in gear.

I have a Sundancer 380 with 8.1S Horizon V-Drives in them. I recently had my shaft and seal replaced in my starboard engine. Since then, when I put in gear (Forward or Reverse) there is a rattling coming from what I can tell is the transmission. The mechanic said it's normal but it wasn't there before they did the work and the port isn't doing it. Any suggestions what it may be and how I can fix it?

Thanks,

SERVICE ADVISORY Date: 11/21/01 Advisory #SV2001-2 SUBJECT: Gear Rattle Hurth Reduction Gear Transmissions--- We have received a number of complaints regarding rattling or noisy ZF/Hurth reduction gears(V-drive or in-line). The noise is most pronounced at idle RPM and typically goes away when the engine RPM is raised above idle. Although the noise can be irritating, this is a normal condition with these transmissions that in no way affects the durability or reliability of the unit. In an effort to reduce the gear rattle noise at low RPM; the transmission manufacturer has suggested that we change from the current Dexron 3 transmission fluid that we use in the transmission to 15W40 motor oil. This is the same oil that we recommend for use in the engine and its higher viscosity helps dampen the contact of the gears and reduces the noise significantly. Indmar has started using 15W40 Pennzoil Marine Motor Oil in all reduction gears starting with engine IC985313. Those units will be identified with a Pennzoil 15W40 Marine Oil sticker on the transmission in place of the ATF sticker that was previously attached. We suggest that if you have a customer complaint of a noisy or rattling reduction gear that you replace the transmission fluid with 15W40 motor oil at the next scheduled service. Our current recommended maintenance schedule calls for changing the transmission oil at the first service(10-20 hours) and then annually or every 300 hours, whichever comes first. Since the transmission has no drain plug, it is necessary to suck the fluid out of the transmission through the opening in the bottom of the filter cavity. Use a suitable oil removal pump with a pick- up long enough to get to the bottom of the transmission housing. You might also want to remove the coolant lines and let the cooler and hoses drain into a suitable container to make sure as much of the fluid as possible is removed from the transmission. It is not necessary to flush the transmission, just get as much of the old fluid out as possible. Reconnect the cooling lines and fill the transmission with 15W40 motor oil. The level of the oil should be between the ìmaxî and ìminî marks on the dipstick. The following chart gives you the approximate capacities of the various reduction gears. Model Capacity450A 2.12 qt (2L)630A 4.2 qt (4L)630V 4.2 qt (4L

Thanks Capt Ron, I appreciate the info. I will change to the Pennzoil motor oil on the next change.

Thank you very much, i have posted about this previously with no success and HERE IS THE answer - at least its an option to see if it works - thank you very much - I have the port rattle and Stbd is fine!!
THANK YOU

curious if anyone has done this yet and the results?? I was speaking with my service tech an said that i might experience a lag in shifting due to the lower viscosity vs. dextron?

Gator said:

Thanks Capt Ron, I appreciate the info. I will change to the Pennzoil motor oil on the next change.

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Having the same issue as this post has mentioned....did you change the oil over to regular ? If so how did it work ?

No, I haven't changed it yet, but the rattling stopped on its own. I will still change it on my next service.

I have this same behavior in the SB ZF HURTH HSW 630 which didnt exist last season but started on the initial shift into gear this season: "The noise is most pronounced at idle RPM and typically goes away when the engine RPM is raised above idle." Its a loud sinosiodal clanking noise, only when in gear, fwd or reverse.

ATF oil level is correct. Is replacing with 15W40 a fix

I am looking for any ZF manuals that could help or fellow SR owners who have experienced this as well.

Here is a video showing the knocking when in gear
https://photos.app.goo.gl/wFkzvZSuQzdMynhq9

I had the rattling occur once during a trip. Traced it down to a chaffed spark plug wire arcing out against the exhaust manifold and dropping that cylinder under load. These transmissions are sensitive to the motors firing on all cylinders otherwise they rattle. The fact yours has just started to rattle leads me to believe something like this has occurred to your motor too.

The main two causes are faulty or improperly seated plug wires or the plugs themselves need replacing. I would firstly check your wires are all seated correctly as your mechanic may have dislodged one whilst working on your boat.

OMG! Not this topic again. STOP!!! The rattle is NOT the transmission and DO NOT CHANGE THE ATF to 30w oil!!!
First, this is normal and as previously mentioned the engine might need new plugs or wires to Smooth the idle RPM. The noise or rattle marble sound is coming from the dampner plate between the engine and trany. The springs get a little loose over time and hence the noise. NORMAL! The 8.1s are so robust that you'd never know if it's running on 8 or 7 cylinders. So when slightly out of tune the camshaft kickback rattles the plate. If anything, pump the RPM up from 650 to 750 and the marble sound will go away!
Been there done that!
Promise!
Mark

Gator said:

Thanks Capt Ron, I appreciate the info. I will change to the Pennzoil motor oil on the next change.

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No!!! Ready my post before you change to oil!!!

This site is dynamite! I had the same issue: The transmission sounded like a box of rocks when in idle in forward gear. No noise in neutral, no noise in reverse. In forward, as soon as the engine RPM was above around 800 RPM, the sound went away. Transmission fluid was filled to the correct level, and the correct bright red color.

Among many, there were two likely possibilities: worn spring on the damper plate, or misfire. I started replacing spark plugs and inspecting each wire carefully. This is what I found on the 7th plug:

That wire had been arcing against the exhaust manifold. I still had an old set of wires. So I changed this arcing wire to one of the old good wires, and changed the last plug.

Issue is resolved! The rocks 'magically' went away.

So the rattle in the transmission was caused by a misfire from a spark plug wire too close to the manifold, that arced through the insulation. At idle speed in forward, the misfire caused the damper plate to rattle on every engine revolution. I posted the picture so that others know what to look for.

So we have another happy camper.

On my third trip with my new to me boat, I thought the transmission was going to explode at idle. I freaked out. The sea trail went well and the 2 1/2 hour ride home was perfect. Thank God I read this forum.

After getting boat home I started on the hit list and I purchased new manifolds and replaced them. The first trip out after this job the boat sounded like the video above and I was in shock. BTW - During my survey I had the surveyor replace the plugs while they were out for compression testing so they were all new. So after reading this I thought no way the plugs are bad after 3 hours. I trusted the knowledge here and pulled them out anyway to see if a bad wire was the culprit. It’s a bitch for me to maneuver in the er. The last plug gave me so much grief but up until now I’m thinking again, no way it’s a plug. Finally I get the last plug out and it is cracked. See pic below. I must have nicked it when I installed the manifold. I had purchased one spare plug and tonight I just finished reinstalling everything and like magic we are quiet as a church mouse!

Thanks to all that posted here and several other posts I read on this topic.

Mark

Interesting. I have developed this noise, and swapped out all new plugs wires, cap, rotor and I still have the rattle. Only in gear at idle.

94SD370 said:

Interesting. I have developed this noise, and swapped out all new plugs wires, cap, rotor and I still have the rattle. Only in gear at idle.

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So all my research was related to the 8.1 motors. I did read somewhere that people found a bad cylinder (low compression) ended up doing the same. Did you verify your compression once you had the plugs out?

boatrboy said:

So all my research was related to the 8.1 motors. I did read somewhere that people found a bad cylinder (low compression) ended up doing the same. Did you verify your compression once you had the plugs out?

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No I did not do a compression test. I did not think to do so.