5LITER
Well-Known Member
My previous car of 10 years was a mazdaspeed6. It also has a getrag transmission and makes the same thuds as my 16 gt. 120k miles later and it was fine until i sold it. I truly believe its a getrag thing.
Sponsored
Reported the parking brake issue when I got my 15 and they said they'd need to keep it at least over night. Just tightened it myself...My 2017 GT PP does this as well. Car only has 420 miles on it. From everything i read this is just a normal sound. Very unfortunate considering this is the first new car ive ever bought. Anyway, taking to the dealer next week to have a busted tail light (lol not joking) replaced. Also, my emergency brake is also really loose. Hopefully they can tighten it up.
This is what I've observed also. The only time I get the "thud" is if I've been sitting in neutral and quickly engage a gear. The location and nature of the sound seem to be the pressure plate and input mass coming to a quick stop by the synchros. Does anyone have the breakaway torque/preload specs for the input of these transmissions?People talk about it being a driveshaft issue, a rear end issue, a transmission issue. And you see some situations of replacing a part and it going away for one guy, but not another. Here's my best guess / theory.
The root cause may be there's some amount of drag across the clutch, even when disengaged. This causes the input shaft of the transmission to spin slightly when in neutral, but being in gear obviously provides enough resistance to stop it. When you're in neutral and move into gear, the inertia of the input shaft transfers to the transmission output. Depending on how much backlash is in all of the downstream components, you'll get a thud of varying degree as that inertia is transferred down the drivetrain and all of that lash is used up, forcing the input shaft to stall. More combined lash means more thudding.
So, if you have low lash in the axle, but a bit in the 2-piece prop shaft, putting in a 1-piece shaft reduces the lash - and the inertial movement - enough to make the thud less noticeable. But if there's also excessive lash in the axle, then you don't make enough reduction in system lash to change how the thud feels. It might be more noticeable off the bat in PP cars because 1) the 3.73:1 gears multiply the axle back lash more than the taller gearsets do, and 2) the Torsen lacks a preload spring, which masks the differential gearing lash in the clutch plate diffs. So, more perceived lash comes from the axle. But you can get it in other axle combinations if the prop shaft or transmission system lash is also high enough. You don't get it in A/T cars because the transmission obviously sidesteps the issue.
I could be completely off base on this, I'm just an axle guy. But this is the only thing I've been able to come up with that addresses all the facts as I understand them. You can chase various aspects of drivetrain back lash and improve the situation, but I'd bet that if the clutch could be set up so the clutch disc more fully disengages the pressure plate, the problem would disappear. At least that's my thinking...
Whats the BG fluid change? Transmission fluid?Mine did it as well I did the BG fluid change and it is almost gone. I say almost because the notchyness is gone but on occasion it does thud just not as bad as it was.
Yes, the fluid properties of the BG fluid seems to tame some of noises from the MT82 as well as improve varying temperature performance. I noticed some noises right away when I purchased my Florida car and drove it in 30 degree new England weather, when I asked the previous owner he was honest and said he never experienced the same noises. My next step I ordered the fluid kit and will be doing the change over in a few weeks.Whats the BG fluid change? Transmission fluid?
And they all stink!So I have to go with the old saying, opinions are like @ssholes....EVERYONE HAS ONE...