02 5MT --> 07 5MT Clutch System Woes
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This is a discussion on 02 5MT --> 07 5MT Clutch System Woes within the Transmission & AWD forums, part of the Tech & Modifying & General Repairs category; Hi. I'm replacing my old transmission ('02 5MT in my wrx) with a newer transmission ('07 5MT from a 2.5RS). ...

  1. #1
    Registered User wreckingball man's Avatar
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    02 5MT --> 07 5MT Clutch System Woes

    Hi. I'm replacing my old transmission ('02 5MT in my wrx) with a newer transmission ('07 5MT from a 2.5RS). I'm having issues with the clutch system and was wondering what could possibly be going wrong with my clutch.

    The problem is: Clutch pedal falls flat to the floor after about 60-100mi of driving losing all pressure. The problem occurs only when the engine is hot, occures mostly/more-often in city driving, and if the car sits for a while the pressure in the clutch pedal returns and all is functional again. So here's a list of what has been done.

    1st - trans swap
    '07 5MT from a 2.5RS
    matching axles
    RS clutch kit
    RS flywheel
    RS slave cylinder
    Trans Fluid
    Clutch Fluid, and bled the clutch system
    The clutch failed about 60mi. down the road
    But pressure in the clutch had been restored by the time i had the car returned to my garage.

    I figured the slave cylinder wasnt drawing enough fluid to operate properly. So I replaced the master cylinder with a 2.5RS master cylinder in an attempt to patch up any compatibility issues in the hydraulic system. This now eliminated two problems which i figured could be occuring: an internal leak in the system, or a compatibility issue between the hydraulic components in the clutch.
    The clutch failed 100mi. down the road, leading to my second fix.

    At this point im completely confused. I figured an incorrect master cylinder was sent to me. So I replaced the master again. I also noticed there was no return spring present on the '07 transmission. So i fabricated a bracket and installed a return spring. And finally, I made sure to bleed the system longer than i would ever consider neccessary making sure all air was completely gone.
    The clutch this time failed 120mi. down the road.

    So here i am now. I figure the only thing left is the clutch hose, so I'll be replacing all the lines. Maybe there's a pinhole leak that formed while i was performing the swap or replacing parts. I cant figure out what could possibly be the cause of the problem. The clutch works, and sometimes it dosnt. Any help would be greatly appreciated.
    Last edited by wreckingball man; 09-09-2012 at 07:25 PM.

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  3. #2
    Good news, everyone! xxxxxxxAnub1s's Avatar
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    Can I ask why you're using a 2.5RS transmission? Cost? Gear ratios? If your WRX tranny blew up due to abuse, don't expect that RS tranny to last very long either. Just fair warning.

    As to your issue, are you losing fluid at all?
    Cody
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  4. #3
    Registered User wreckingball man's Avatar
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    The main reason was that the RS trans was over $1,000 cheaper, had very few miles on it, about 40,000 and it was in great condition. It also had the same FD ratio on it, so i figured it would be a good replacement. The '02 WRX tranny had 250,000 miles on it...so I would expect to get about the same.

    I'm not losing fluid at all. Everytime the clutch lost pressure the first thing i did was check the reservior and it was at the correct level every time. So ive about lost hope lol.

  5. #4
    Registered User wreckingball man's Avatar
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    I wouldnt consider the transmission to be part of the problem because it's essentially the same trans.
    Could there be other components in the clutch system that are not compatible that would cause this?
    Do you think I'm on the right track with replacing the hose? Becasue this problem is symptomatic of an internal leak or air leaking into the system. I think this is the most probable cause.
    Also, someone told me I may need RS pedals as well, but that seems kind of odd...?

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    Registered User wreckingball man's Avatar
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    Didnt need pedals. of course lol. the clutch hose was rotted out. replaced the clutch hose. now everything works beautifully. this thread may be useless now.
    Last edited by wreckingball man; 09-19-2012 at 01:08 PM.

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