LWF rattle and higher viscosity transaxle oil

I recently installed an Aasco LWF with a sprung hub clutch kit (SPEC 1). When engine/trans is cold, no rattle at all. As it warms rattle gets worse and worse under any load and the RPM range gets broader as well. It is obvious that as the trans. oil gets warmer, the rattle gets worse so a more viscous oil will dampen the vibrations. I spent a while online researching and all I could find was a BMW shop website discussing it. They confirmed what I thought and suggested a mix of Redline 75W140NS gear oil and Redline D4 synthetic ATF. This is for a regular transmission, not a transaxle. Does anyone have any experience or knowledge of whether this would work well in our Getrag transaxles or what is the most viscous fluid we should use and still provide proper lubrication and function of the synchros? I would wager that the same "recipe" would work in ours, but hoping for more educated input. I have a Wavetrac dif and am currently using Redline 75W90NS which worked great prior to LWF install.

It requires a delicate balance to create a fluid that works with both a hypoid (differential) gear and synchromesh at the same time. Playing amateur chemist in an effort to quiet down the gearbox would sooner or later become an expensive lesson in why that is so. Having replaced a transaxle now, I just let mine rattle.

So did you use higher viscosity to fix rattle and mess it up or did it fail for another reason? Is there already a thread about this? I'm not worried about synchros with this combo as it was recommended for BMW Getrag transmissions which I would think have the same or very similar synchromesh system. Anyway, I'd be curious to hear your story.

I did some more research. Wavetrac lists 75W140ns oil as compatible. I found a few threads of people with track/race cars running it in their Porsches so I'm going to go for a 50-50 mix of 75w140ns and 70w90ns as the BMW thread suggested. Hopefully will cure the rattle and still shift fine.

The rattle is due to the LWFW, not balancing the harmonics like the dual mass OEM one did, not the transmission. Mixing fluids is a no-no. I have a Wavetrac and I use Motul 75W-90 without any rattle. I did replace my clutch plate when I had the Wavetrac installed. I asked my shop about installing a LWFW and their suggestion was the only benefit is in 1st gear from a stop light and you get a rattle that will drive you nuts. Use Google and search about LWFW's in a Cayman and you will find your answer. I would change that oil back to factory specs. I'm using Motul only because Wavetrac said it works well for both the LSD and the 6 speed transmission. I do not have any issues yet after 2 years of use with this setup.

Please can you explain how a single mass flywheel such as the Aasco item can rattle ? Actually, let me help you, it can't. If it were the flywheel rattling, it or the clutch attached to it, would have to be loose. The rattle you're hearing IS the transmission, specifically the the backlash between the gears on the mainshaft and those on the layshaft. Any internal combustion engine will produce pulses as a result of the combustion taking place in the cylinders when it's running. And whilst those pulses will be barely discernible, if indeed at all, to the human ear, rest assured there are hundreds of them every second. As each cylinder fires in turn, it produces pulses which create torsional anomalies along the length of the crankshaft, and at certain engine speeds, the frequency of the those pulses and the torsional anomalies they produce, could and would eventually cause the crankshaft to fail due to fatigue. The flywheel on an engine damps the firing pulses and helps smooth them out. The original dual mass flywheel is constructed in such a manner that it not only smooths out the power pulses, but it specifically counters the torsional anomalies and effectively cancels them out. When you substitute the dual mass flywheel for a single mass flywheel you lose a large majority of the smoothing effect AND the dampening effect of the crankshaft. With a lightweight, single mass flywheel fitted, and the power pulses no longer smoothed out as intended by the manufacturer, the crankshaft is effectively accelerated and deaccelerated when each cylinder fires, unfortunately this means the shafts (and specifically the gears attached to them) in the gearbox are also being accelerated then slowed, and as the gears have a certain amount of backlash between them, this constant acceleration and deacceleration can cause them to resonate and "rattle". And it's that rattle you can hear when the transmission is hot, because the ability of the oil to lessen the resonance between the gears is reduced as it thins with heat. It's also why the rattle will all but disappear when you depress the clutch.

So in essence my shop, Cantrell Motor Sports in Bellevue, Wa, just cut to the chase and told me the outcome rather than the particulars on how the rattle works. I am glad I don't have a LWFW although I thought about that change due to a lot of stop and go freeway traffic issues where the rattle would manifest itself. Thanks for clarifying how the transmission is actually the culprit, not the flywheel. My flywheel was in perfect shape when I had my clutch changed at 40k miles, so I just used Sachs clutch kit, and the addition of the Wavetrac LSD to the transaxle. While the spin up in 1st gear with a LWFW is a little less than a dual clutch system, the Wavetrac makes two black marks on the pavement for a quicker start after dumping the clutch at 4500. I've added a Function First motor mount Orange insert and their transmission mounts to prevent wheel hop. All seems to work well with a little more NVH, especially on startup. This system also works well preventing engine movement in quick transitions as in slalom type road features. Biggal76; Motul 75W-140 gear oil would be a halfway solution to reduce the rattle in a LWFW application. It may be a little sluggish shifting when cold though especially downshifting into 1st gear, depending on the temps where you live. I'm sure you have made the oil change a month ago. Let us know your outcome please.

The Wavetrac is an excellent upgrade, as are the Function First motor and trans mounts Did you notice any increase in vibration through the driveline after fitting the mounts ?

I do have more vibration around 15-20 mph under power, but dissipates rapidly after that speed. I attributed it to the harmonic balance of the Wavetrac unit, not the transmission mounts. Could be a combo of both I guess.

I can confirm it's the mounts as opposed to the Wavetrac that cause the vibration, added to which the Wavetrac if correctly installed shouldn't produce ANY driveline vibration at all.

Ok, Henry. I had the motor mounts and transmission mounts installed along with the Wavetrac and clutch plate kit a same time. So I could not tell which was causing the slight vibration at 15-20 mph.

I concur, the Wavetrac isn't the culprit (I have one). I have Function First transmission mounts (not the inserts. I sent in my OEM mounts and they remanufactured them with more rigid material). The NVH was bad form the trans mounts until I changed my clutch/flywheel and discovered that my OEM flywheel was not working properly. NVH is 80% improved since I installed a LWF with sprung clutch but now I get the transmission vibrating as Henry explained. I replaced 1/3 of the fluid with 75W 140 gear oil and there was significant improvement but it still does it. I'm going to go ahead and drain it all and fill the whole thing with 75W 140 eventually and I suspect there will still be a hint of the rattle but it won't be bad. When you start with the mods, weird stuff happens.

I agree with your assessment of using only 75W 140. I would go with Motul as Wavetrac speced this oil for their race useage. The down side of this oil and others with this weight is being able to downshift into 1st gear, especially when the transmission is cold. I just refreshed my engine oil with Motul 300V Power 5W 40 and found that the engine NVH is less with new oil after 4000 miles on the old oil. So, I will refresh this oil again at 3500 next time. I did change the oil filtration system to a LN screw on filter. This new cartridge filter is physically smaller than the OEM canister paper filter and potentially gives more PSI due to less filtration. That's speculation on my part and leaves me open to better ideas as to why the engine sounds quitter. I do know that LN suggests this kit to help reduce #6 rod bearing scarring when tracking the car by adding PSI due to less back pressure through the filter. I changed to FF Orange motor mounts inserts to reduce engine motion, but when the shop pulled out the motor mount, they found it cracked and broken down at 40k miles. I actually saw it as I was waiting on the car. Luckily, Cantrell had a delivery from a supplier on its way and they threw in a OEM motor mount. So 1 1/2 hours later, I was out the door. NVH was higher for about a month with the new motor mount/FF insert, but did smooth out. I am not a critic about NVH if the parts do their job, I believe the FF Orange motor mount insert accomplishes the job along with their transmission mounts. But Henry does point out that low speed vibration is noticeable with the FF Orange transmission mounts. Let us know how your 1st gear synchro is affected by the heaver wt transaxle oil. Not sure about your shifter and cables, but the Numeric system really works well and can overpower the synchros in certain situations, so I do double clutch in some race situations, but a lot of my car's usage is on the street, which does not need that urgency. Although I do use downshifting on the street vs braking is to keep oil on the cylinder walls and down shifting does this. Seems to work as I have 0 oil usage between oil change, which means the rings and cylinder walls are in good shape. Fingers crossed regarding bore scoring issues using a M97 engine.

Henry, You live in England somewhere? Just give us your appreciation of the Wavetrac LSD. Where are you finding the best uses and what really surprised you after it's install? I'm finding an under-appreciation of the unit on P9 and no real idea where it could be of greatest benefit. Especially when the cost of installation is high and the benefits are hidden from view. Not many owners of the Wavetrac jump up and down over its usefulness. I certainly can attest to its unique ability to put down power without wheel spin. And that power to the ground only slightly affects oversteer as it does not lock up 100% like some clutch units do. I would like to hear your impression from Europe.