ZF 84 IV transmission is noticeably quieter

M

mrsrobinson

Well-Known Member
Mar 9, 2006
7,704
Virginia
Boat Info
2001 380DA
Engines
Caterpillar 3126
The previous owners of my boat replaced the original Port transmission, ZF HSW 800 VI, with an updated model, ZF 84 IV. For the first time recently I noticed a difference in the noise level between the two, the updated port one is much quieter when idling. I've always said the transmissions are louder than the engines at idle on all of my v drive boats, this transmission you can barely hear at idle.

Just sharing...
 
A lot of the noise at idle comes from old/bad damper plates. They are pretty cheap to buy, but you have to separate the engine and tranny to replace.

If the noise subsides at a slightly higher RPM, that's a damper plate issue.

Transmission itself shouldn't make much noise at all.

If you find the noise subsides at a slightly higher RPM, you can adjust the idle speed on the engine.
 
Last edited:
dtfeld said:
What are your IDLE RPM? Adjusting to 700-725, may smooth things out, quiet things down.

http://www.clubsearay.com/index.php?threads/official-caterpillar3116-3126-thread.102850/page-10
Click to expand...

That made a big difference in ours, probably in noise levels but the most noticeable improvement was the vibration at idle went away completely once I brought them up to 700 idle. The previous owner had them at 650 and the whole boat shook, especially in gear as the revs would drop to 600 or so idling around the marina and channel
 
Hmm, I did notice mine were idling high when coming back to the slip last weekend, over 1,000 rpms. They were idling at 700 during sea trial a few months ago. We do have some vibration at idle as well. I have always heard the v-drives at idle speeds in my boats. In this particular boat the upgraded newer transmission is much quieter.
 
mrsrobinson said:
Hmm, I did notice mine were idling high when coming back to the slip last weekend, over 1,000 rpms. They were idling at 700 during sea trial a few months ago. We do have some vibration at idle as well. I have always heard the v-drives at idle speeds in my boats. In this particular boat the upgraded newer transmission is much quieter.
Click to expand...
1000 is a little high… did you replace the tachs?
 
No, we did some of the 1,000-hour service a couple weekends ago, but I didn't pay attention to the idle speed until coming in last weekend, felt like I was moving a little faster than usual and I noticed both were over 1,000 RPMs.

I noticed how much quieter the newer transmission was at the same time as I was shifting both engines into neutral at different times to slow my speed down.
 
mrsrobinson said:
No, we did some of the 1,000-hour service a couple weekends ago, but I didn't pay attention to the idle speed until coming in last weekend, felt like I was moving a little faster than usual and I noticed both were over 1,000 RPMs.

I noticed how much quieter the newer transmission was at the same time as I was shifting both engines into neutral at different times to slow my speed down.
Click to expand...

1000 is high, especially in gear. First check the throttle arm at the governor (with the throttle pulled all the way back) and make sure it’s hitting the idle stop
 
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