Transmission Noise

wwaseleski

New Member
Jul 6, 2016
8
Connecticut
Boat Info
1995 Sea Ray 400 Express Cruiser
Engines
454 Mercruisers, Inboard
I have a 1995 Sea Ray 400 EC, 454ci. mercruisers, Hurth ZF HSW 630 A-1 , 2.04 Ratio Transmissions. When cruising at idle (600 RPM) the starboard transmission makes an intermittent rattling noise. As soon as you increase the speed (800-1000 rpm) the rattling stops completely. The boat runs fine cruising at 3200 RPMS. I changed the filter, no chips, the fluid was clean. Should I be concerned ??
 
It could be a cylinder not firing. At lower RPMs that "miss" is transferred more noticeably to the transmission. When you throttle up, the miss isn't as pronounced because it's shorter in duration and you didn't hear/feel it. Try checking your plugs/wires. That's what I ran into.
 
What Dale said is correct or It
can be the transmission damper plate that has five or six springs on them that I’ve been known to crack and rattle at a low r.p.m.
 
I had the issue that you describe, like Dale said, I changed the plugs and the rattle went away.
 
SO... I have asked this a couple of times on here as I have an '05 420 DA with 8.1's and have the same issue with only my port transmission! It is having the same issue and has all summer long! Just in the last couple of months the "rattling" has lightened and a "low level whine" has started. I have asked so many "knowledgeable" techs and people about this and received the same response that it is/was the dampening plate and or springs rattling around.
So... i still do not have a definitive answer to my problem or yours but mine has not got me concerned that it is getting worse whatever it is as the new whining noise concerns me that it might be something worsening in the Zdrive tranny. It still shifts fine and runs fine.
As with yours the fluids are clear and its not an engine issue - the plugs were changed, injectors changed with the 8.1 fuel rail recall and she is making good wot power!!
Any other thoughts????
Chris

What Dale said is correct or It
can be the transmission damper plate that has five or six springs on them that I’ve been known to crack and rattle at a low r.p.m.
 
C3B49088-512B-4AB9-94F5-014A419D1003_sRGB.JPG

Idling at 600 in gear is on the low side. I would adjust the idle up a bit to 750-800 and see if it goes away. This noise is very common and not necessarily a sign of something wrong. All of my trannys did this when RPMS were off, even with brand new boats. As mentioned, tune state, and bad plugs, can cause it. My 8.1s were so robust that I sometimes waited for a little rattle before replacing plugs. That was an early indicator that it was time to change them.
 
SO... I have asked this a couple of times on here as I have an '05 420 DA with 8.1's and have the same issue with only my port transmission! It is having the same issue and has all summer long! Just in the last couple of months the "rattling" has lightened and a "low level whine" has started. I have asked so many "knowledgeable" techs and people about this and received the same response that it is/was the dampening plate and or springs rattling around.
So... i still do not have a definitive answer to my problem or yours but mine has not got me concerned that it is getting worse whatever it is as the new whining noise concerns me that it might be something worsening in the Zdrive tranny. It still shifts fine and runs fine.
As with yours the fluids are clear and its not an engine issue - the plugs were changed, injectors changed with the 8.1 fuel rail recall and she is making good wot power!!
Any other thoughts????
I will tell you that I had the same rattle all summer 2016 turned out I had a dead cylinder and wound up blowing up the valves
Had I done a compression test I would’ve seen the issue, I believed it was a broken spring On the damper plate... might be able to see them through theinspection hole in the bell housing


Chris
I will tell you that I had the same rattle all summer 2016 turned out I had a dead cylinder and wound up blowing up the valves
Had I done a compression test I would’ve seen the issue, I believed it was a broken spring.... might be able to see them through theinspection hole in the bell housing
 
Last edited:
View attachment 94207
Idling at 600 in gear is on the low side. I would adjust the idle up a bit to 750-800 and see if it goes away. This noise is very common and not necessarily a sign of something wrong. All of my trannys did this when RPMS were off, even with brand new boats. As mentioned, tune state, and bad plugs, can cause it. My 8.1s were so robust that I sometimes waited for a little rattle before replacing plugs. That was an early indicator that it was time to change them.

600 rpms in gear does seem a little bit low.
 
650rpm in neutral and 600Rpm in gear is spot on for the 7.4 8.1 and 8.2
 
650rpm in neutral and 600Rpm in gear is spot on for the 7.4 8.1 and 8.2
C3B49088-512B-4AB9-94F5-014A419D1003_sRGB.JPG

650-800 in forward gear is what the Crusader manuals say for the 454, 8.1 and 8.2 engines according to their web site.
 
upload_2020-10-30_1-9-23.jpeg


1995 Merc. standard HP 7.4L 650-700 in gear.

The noise is normal but, will lessen with a higher idle and a perfectly running engine.
 
I think the real question is, did it just start making noise or has it always been that way?
 

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