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RIP: MY00 BRP 2.5RS Sedan 4EAT
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Discussion Starter #1
Does anyone ever notice a quick sucking noise on their 4EAT when they go WOT and it shifts from 1st to 2nd. It happens between that shift. I've rode in brucelee's car and he mentioned it to me and i noticed it too.. I've always heard it on my car but didn't really think it was important. i think the sucking noise is from my exhaust like it closes up between the shift. i don't know if its the exact same noise that brucelee was talking abt. regular driving, you cant hear it.. only when you are WOT. anyone notice this? what could it be? whats happening?
 

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1999 Forester
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126 Posts
I know it's old, but I am bringing this thread back from the dead. I just started getting the same thing yesterday. Launching from a dead stop, when the car shifts to 2nd, I hear a "PFFT!" sound, almost like a really weak blow-off valve. Seems to happen only when the car is cold.

Anyone in the last 7 years figure this out?
 

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Big Bad BH "Slow White"
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169 Posts
Yeah, the 4EAT does suck, but I didn't think it made a noise... (sorry, it was easy, I had to)

I haven't noticed that quirk on mine but I don't go 1-2 at WOT a lot. I'll listen for it next time though.
 

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1999 Forester
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126 Posts
I did some digging, and the guys on SubaruForester.org say it's actually on the 2-3 shift, and its the center diff transferring to 90:10 FWD from 50:50 AWD.
 

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'99 OBS
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117 Posts
The 4EAT was remapped in the 99MY and part of that was to lessen the shift shock on upshifts. The TCM is connected to the ECU and is capable of cutting fuel momentarily as the trans shifts - maybe this is the source of the noise?

The SubaruForester.org info could be correct, but likely only for more recent models with a true center diff. The older MPT cars are pretty quiet - not to mention, I've driven around and monitored the duty cycle of the MPT's AWD transfer solenoid, and I can tell you that it gradually varies the torque split. It doesn't just switch from one 'setting' to another.

That said, I've never heard the noise on my car, so I could be way off base.
 
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