Hello folks,

since I installed a lightweight flywheel (19 lbs) I have this light drivetrain noise (buzzing/rattling) up to ~2500 rpm with high load. However, I noticed it is almost non-existant when it is cold outside and for the first few minutes of driving. I assume it has to do with the viskosity of the transmission oil.

Has anyone tried different tranny oils and had success reducing this specific drive train noise?

Thanks.

 

Would you like to spend 65 dollers on tranny oil? if so go to splparts.com and buy the tranny oil called NEO

 

why would the tranny fluid have to do with it?

 

thicker fluid might help?

 

Many members regret getting a lighter flywheel for the added chatter

 

No, the tranny fluid won't make any difference. Did you even bother reading the subject? What the hell are you doing giving automotive advice? To the OP, and others who don't know, the flywheel is NOT immersed in any kind of gear fluid!

 

Might be because the engine is idling higher before the engine is warmed up.

TK

 

I guess we are all pretty well aware that the flywheel is not immersed in any kind of gear fluid. However the noise doesn't originate from the flywheel either, so I guess that it is a valid assumtion that it might come out of the gear box and therefore the viskosity of the tranny oil might very well affect the cause (clearances?) that creates the noise in the first line or make a difference in how the noise is being dampend.

I wonder that no one has experimented with the oil yet.

 

I assume it has to do with the viskosity of the transmission oil.

 

When my roommate dropped a lightweight flywheel (9 or 12 lbs, can't remember) in his '99
M3 a local shop recommended that he use some heavier gear oil to help reduce the chatter.

He ended up using a half and half mix of Redline MTL and Redline Shockproof. It definitely
helped reduce some of the cement mixer noise.

The Getrag transmission in his M was a little less particular about the gear oil used though.
I'm not sure if using the thicker stuff in a Z transmission might cause problems with the
syncros down the road (since the factory oil is 75w80).

-Ben

 

turn up the stereo or get a nice loud exhaust

 

Don't worry, loud exhaust is in place already, still... Thanks to ingramstar01 for the suggestion.

 

Silo, you are correct. The viscosity of the gear oil in the tranny is related to the gear noise. I didn't go thicker, but I switched to Redline MTL and it helped a bit when I had the ACT streetlite flywheel. I didn't want to go too thick on the oil, so I removed the flywheel. It's easier to try different oils, so why not try. I had an opportunity so I took it off.

 

...raise your idle rpms

 

Thanks for the input billybrun!

@sentry65: How would raising the idle help? The noise is up to 2500! I don't see how raising the idle would help - and how much raise are we talking?

 

My apologies! Lighter flywheels do transmit all the crankshaft's torsional vibrations straight through to the gears. Since gear chatter, especially at idle, is the most obvious symptom, and it is prevalent across almost every make and model of car made, I assumed everyone knew that changing the oil has not made much of a difference for anyone. Gear fluid is already pretty heavy, and most people that install a lighter flywheel can be expected to have some good synthetic in there, so not sure how much better or heavier oil you can put in. Sounds like a good project for experimenting.

 

The chatter I thought was due to the design of aftermarket flywheels compared to the factory flywheel. The factory utilizes a daul mass flywheel to significantly reduce vibrations... whereas aftermarket flywheels do not as it makes it heavier as well as more costly, and one who wants little to no noise should not upgrade the flywheel, and those that do buy an aftermarket flywheel and have done their homework should realize there is an increase in chatter that is audible. Doing an upgrade such as this is not for the man who wishes to cruise down the highway talking on his cell phone on a business call while drinking coffee, but rather for the enthusiast that doesn't mind how loud it is because he just passed that cherry colored M3 and walked away from him like he was an old stanza.

 

Well XIceDragonX your comments sound as if you never had a lightweight flywheel in the Z. There is absolutely no noise when you "cruise down the highway"; and on my car there is also no extra noises at idle as undrgnd mentioned.

The noise comes on when you accelerate and up to 2500 rpm only, then they are gone. You can also avoid the noise if you accelerate very lightly but that might not be practical in all situations.

Is 75W80 that heavy of a tranny oil btw?

 

Silo, "Especially" at idle, is the key word, but not exclusively. 75W80 is too light from what I've read. I installed a 50/50 mix of Red Line synthetic 75W90 and MT90, when I first purchased the car. The tranny shifts like a dream and has never made any noise. HOWEVER, I still have the OEM flywheel. I don't know that changing the fluid will make any difference in the noise, but it certainly will not hurt in other aspects.

 

Cool, thanks for the info on your oil blend!