I noticed something else interesting earlier today while I was changing my oil and coolant. While I was sitting in the car waiting for the engine to warm up to bleed the cooling system with the front end still jacked up, I got bored and ran it through the gears. I noticed that the transmission whines somewhat while spinning the wheels, especially in 5th gear (presumably since the output side of the trans is spinning the fastest). But what's really odd is as soon as I push the clutch in, that whining noise goes away or at least gets quiet enough that I can't hear it over the engine/exhaust noise even though everything in the trans is still spinning. But as soon as I let the clutch out, the noise is back. That doesn't make any sense to me because everything in the trans is still spinning with the clutch pushed in until the wheels come to a stop. I'm not overly concerned about this, but I'm really curious why disengaging the clutch would make the trans so much quieter despite the fact that everything inside the trans is still spinning. Anyone have any ideas?
Normal manual transmission noise?
- Thread starter Avery4
- Start date
Just got the Amsoil Synchromesh fluid and the transmission seems to like it. It now goes into gear easier and smoother and 1st gear seems a little easier to engage while moving. The transmission also seems somewhat quieter when downshifting as well as when idling in neutral. Neither of those noises have gotten any louder since I installed this trans.
I haven't driven it long enough to know whether the transmission's temp is any lower or higher with the Amsoil fluid, but I will report back once I do. The hottest the Honda MTF normally got was around 150-155 degrees and the hottest I have ever seen it is 179 degrees, but that was when I was towing another Civic home through the great smoky mountains in 90+ degree weather so somewhat higher temps aren't surprising.
I haven't driven it long enough to know whether the transmission's temp is any lower or higher with the Amsoil fluid, but I will report back once I do. The hottest the Honda MTF normally got was around 150-155 degrees and the hottest I have ever seen it is 179 degrees, but that was when I was towing another Civic home through the great smoky mountains in 90+ degree weather so somewhat higher temps aren't surprising.
Why do you think it doesn't sound like a good idea? The only disadvantage
of slightly overfilling a manual gearbox is a marginal increase in fluid drag.
How should it be any different? Shifting may feel different, it may sound a little
smoother if you went thicker, but I doubt there will be any perceivable change
in temperature unless you went wayyyyyyy thicker or thinner. Temp variations
due to varying environmental temps and even minor changes in driving are far
far greater.
.
I'm no engineer, perhaps in some applications that is true. However, what I do know is that an overfilled transmission will run hotter from the extra drag and I would think there could also be issues with the fluid foaming/becoming aerated like in an overfilled engine from gears/other moving parts being submerged in the fluid further than intended. The fluid obviously won't be a very good lubricant if it's full of bubbles. How much are you suggesting overfilling the fluid by? Are we talking an extra few ounces or an extra quart?
I believe you are totally correct, I was just curious to see if the temp would change from reduced friction/more viscous drag but it doesn't look like it did. If anything it may be running a few degrees cooler under similar conditions as the highest temp I have seen with the new fluid is 151 rather than 155 on the same route at the same speed with similar 90+ degree weather, but differences that small are well within normal variance so I can't claim anything definitively.
A transmission isn't a combustion engine. Slightly overfilling means less than half a quart.
Over the years I was talking about this specific questions with ZF, VW and Getrag engineers
several times. Reasonably overfilling is basically what they suggested.
Depending on the locations of the fill plug it could be somewhat hard to overfill it anyway.
It's fairly easy in case of my Mini's Getrag and even easier on my GTI since I have to remove
a guide pin/bolt sitting on top anyway and fill from there (VW actually skipped the fill plug
bore around 2016/17, I was probably the first who noticed that). Not so easy on my Porsche
though, but it isn't driven hard, so it doesn't matter.
Over the years I was talking about this specific questions with ZF, VW and Getrag engineers
several times. Reasonably overfilling is basically what they suggested.
Depending on the locations of the fill plug it could be somewhat hard to overfill it anyway.
It's fairly easy in case of my Mini's Getrag and even easier on my GTI since I have to remove
a guide pin/bolt sitting on top anyway and fill from there (VW actually skipped the fill plug
bore around 2016/17, I was probably the first who noticed that). Not so easy on my Porsche
though, but it isn't driven hard, so it doesn't matter.
Hmm good to know. Overfilling the transmission is not particularly difficult on my car, it is easily accomplished by tilting the car to the passenger side (the side the fill plug is on) is highest. Or even easier, just take the breather cap or speed sensor out and pour the oil in either hole. The way I normally fill the transmission is actually through the breather cap port with a hose and a funnel until it runs out of the fill hole as it is much easier and less messy than trying to pump the fluid into the foll port on the side.
What exactly does overfilling the transmission accomplish? Is the idea that a higher oil level will submerge parts such as bearings that may otherwise only be lubricated by splash? Or to create more splash?
That's exactly my prefered way to fill a transmission - using a hose and a funnel.
The beauty is, the hose is sitting tight in the fill hole of the Mini Getrag, while the
differential is pretty close behind the fill hole, so that "excess" oil is just slowly
draining out of it after removing the hose, making it easy to overfill as desired
without a need to tilt the car, which isn't that advisable when using a lift anyway.
It'll probably submerge some more parts and helps routing oil to not submerged
bearings (because most of them are not). Yes, more oil leads to more splash. As a
side effect, more oil also aids cooling because more oil transfers more heat to the
gearbox case, much more than changing oil spec ever could. Gear oil is a much
better thermal transfer media compared to air. That's rarely the main purpose of
overfilling though.
40 or 30 years ago transmission oil fill levels have been tuned to lubricate as good
as possible and often a tad more before CAD was invented. Today fill level is often
reduced just to utilize any chance reducing emissions and increasing efficiency. Less
oil makes for less fluid drag and that makes for less emissions. The gain is very very
little (much less than one single mpg) though, but every single drop of fuel counts.
.
The beauty is, the hose is sitting tight in the fill hole of the Mini Getrag, while the
differential is pretty close behind the fill hole, so that "excess" oil is just slowly
draining out of it after removing the hose, making it easy to overfill as desired
without a need to tilt the car, which isn't that advisable when using a lift anyway.
It'll probably submerge some more parts and helps routing oil to not submerged
bearings (because most of them are not). Yes, more oil leads to more splash. As a
side effect, more oil also aids cooling because more oil transfers more heat to the
gearbox case, much more than changing oil spec ever could. Gear oil is a much
better thermal transfer media compared to air. That's rarely the main purpose of
overfilling though.
40 or 30 years ago transmission oil fill levels have been tuned to lubricate as good
as possible and often a tad more before CAD was invented. Today fill level is often
reduced just to utilize any chance reducing emissions and increasing efficiency. Less
oil makes for less fluid drag and that makes for less emissions. The gain is very very
little (much less than one single mpg) though, but every single drop of fuel counts.
.
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Exactly how loud is acceptable for a manual transmission? I just got my K24 swapped 04 Civic running and its transmission makes an obviously audible noise when idling in neutral with the clutch engaged, way louder than my 05 Civic. The type of noise it makes doesn't sound particularly nasty, but the fact that it's loud enough to clearly hear inside the cabin even over the open header is somewhat disturbing.
This transmission is from an 06 Acura RSX with supposedly 147K miles on it. Input shaft felt solid with no play. For some reason these K series transmissions don't seem to have the issues with input shaft bearing failures that the D series Civic transmissions do.
This transmission is from an 06 Acura RSX with supposedly 147K miles on it. Input shaft felt solid with no play. For some reason these K series transmissions don't seem to have the issues with input shaft bearing failures that the D series Civic transmissions do.
In a synchromesh transmission, all of the power transmission gears are engaged all the time. The synchronizer engages the shaft to a particular gear. Said gears wear into a pattern with each other. Once you replaced the input shaft bearing and reassembled, you practically never get exactly the same gear meshing pattern in the tranny. That is the whirring you are hearing. Once the gears go on load, the whirring can decrease as the loading affects the meshing surface action. Same thing on rear end differentials. Once you disassemble, then reassemble, I have never seen a ring and pinion mesh exactly like they did before; hence a little noise from the differential.
Never thought about that but it makes sense. I noticed that the same transmission has a bit of a rattle when spinning under no load such as when idling in 5th gear with the wheels off the ground but from my understanding that's pretty normal, it never rattles while driving.
As described in post #49, the RSX transmission in my K swapped 04 Civic is much louder than the transmission in the 05 Civic I originally asked about and to the best of my knowledge it has never been apart but I have no way to know it's history since I bought it used.
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