I get a lot of emails asking for my opinion on "is this normal noise" so I wanted to make this blog post all about the what noises are normal when you swap to a performance manual transmission setup.
Let's talk about how and why you might get noises from your transmission.
If the noises you are hearing are during a lugging engine condition then I would say you are hearing normal sounds from a 2JZ with a non-dual mass flywheel and manual transmission. Watch the videos below and tell me if the noises you are hearing are similar to these. If so, likely it could be possibly gear rollover noise.
This is a standard noise on a 2JZ with a single mass flywheel. Basically all the engine harmonics are allowed to come straight back through the trans as there is no dampening between them. So anything engine/tune wise that is off, like choppy idle, low rpm idle or lean conditions etc can make the noise even more exaggerated. Rollover noise is common at idle and during low rpm during lugging conditions (2200-2800rpm typically).
It can seem like something is wrong, but it's basically the engine chattering from being in a less than ideal operating condition and its "chugging" and the harmonics translate through the gearbox by chattering the teeth of the gears. This noise is NORMAL and avoidable with a downshift to get the engine in a more ideal operating range.
The noise stems from the lack of a dampening system between the noisy JZ motor and the big transmission with large gears and large tolerances in those gears. Basically without a (dampened) dual mass flywheel the engine harmonics translate directly through the driveline. No performance clutches use a dual mass flywheel as they can separate/explode, as it's basically rubber holding it together the two pieces... so on high HP applications it's not a good fit.
Video Ryan Scott did of an RXT clutch on the Magnum
All the kits I sell are designed to perform with high horsepower while trying to keep NVH to lowest possible amount possible in a setup like this. However, there are a few things that are unavoidable in a high performance manual transmission. Here are few things that can and will lead to more noise than a stock manual transmission or automatic car.
1. Most common -> No dampening on the clutch. A stock dual mass flywheel absorbs a ton of engine harmonics, when a performance clutch is installed with a single mass flywheel (literally every performance clutch) then there will be engine noise/chatter/harmonics that is going to translate back through the transmission. This is especially noticeable during a lugging condition when the engine is saying "downshift, downshift!" you would not get this same noise in an automatic transmission because it would have already downshifted to get the engine into a more ideal operating range. The lighter the flywheel, the worse this noise becomes. I try to keep my flywheels a bit more close to stock weight to try and keep them street friendly. See video at bottom for more...
2. No dampening remains in the one-piece driveshaft. The stock driveshaft is a two-piece unit with a carrier in the middle and a rubber guibo on the diff flange. This helps isolate noise from the diff translating back up through the transmission just like a dual mass flywheel does on the engine side. All performance driveshafts will have this same setup, they are not going to leave anything in there that can break/tear under power. So this will also contribute to more noise in the setup
3. Stiffer, more solid transmission mounting. OEM mounts are super soft rubber, which helps dampen more noise, but they also tear when the engine torques. I have my softer rubber mount that is used in almost all my kits but it is quite a bit stiffer than a stock mount so that it does not tear or wear out like a stock mount would. Again, this leads to some more noise translating through the chassis
4. TREMEC's Direct mounted shifter. This shifter is unlike most you would see setup on a tripod behind the trans. Tripod shifters have bushings and more isolation from the transmission noise so you will not get as much vibration through the shifter handle and you will get a little less noise as its more seperated from the transmission case and gearset noise. However, tripod shifters also tend to flex, and have play in them, and they can cause lockout issues on gears on a hard turn if the chassis flexes mid-shift. The direct mounted shifter is a much better setup for a performance car, but again it has a slight disadvantage in noise and vibration.
5. Bad balancer. If your car is on the factory crank damper pulley this can also cause more vibration as those tend to fail and fall apart. OEM balancers are a high risk item on a modded car. I recommend an ATI super damper on all performance cars.
6. Low idle, super choppy idle. This is a simple one... if you idle is super low (for example on a JZ engine) at 800rpm, its going to chatter. Turn the idle up to 50-100rpm at a time until you find the best combination of low driveline sound and best idle properties. If you really want to hear an example of extreme rollover noise, put the car on a lift or on jack stands, and put the car in 1st gear and let out the clutch and let it idle on the lift in first gear. This will cause load a heavy lugging condition similar to if you were in 4th gear and only going 30-40mph... and you'll hear the engine struggle, and that translates directly into the transmission chattering. I don't recommend this... but i have had guys send me videos of exactly this thinking they have a problem with their transmission.
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I can tell you this, I have driven almost every manual transmission behind a 2JZ engine. Getrag V160/V161, R154, W58, T56 Magnum, Nissan CD009.... When you do the same stuff, single mass clutch, no dampening... on ANY of those transmissions they make same noises. Now, the magnum is a bit louder but that is because it has MASSIVE gears in it. So it is the same concept as a bigger diameter exhaust... more noise comes with it... but these transmissions are reliable and durable in high horsepower applications.
Hopefully this article helps to ease your mind and helps you understand why the noises do happen.
- Joel Grannas
Video of lightweight flywheel on 2JZ engine
