# WTF Shifting vs Boost issue

**URL:** <https://forums.speedlife.net/t/wtf-shifting-vs-boost-issue/215836>\
**Category:** NYSpeed Automotive\
**Created:** [August 24, 2011, 5:42pm UTC](https://forums.speedlife.net/t/wtf-shifting-vs-boost-issue/215836 "2011-08-24T17:42:02Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Z31NA2T](https://avatars.discourse-cdn.com/v4/letter/z/e495f1/32.png) [@Z31NA2T](https://forums.speedlife.net/u/Z31NA2T)\
**Post date:** [August 24, 2011, 5:42pm UTC](https://forums.speedlife.net/t/wtf-shifting-vs-boost-issue/215836/1 "2011-08-24T17:42:02Z")

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I’m not one to normally ask questions, but this has me stumped. My 86T will build full 10psi of boost in 1st, 2nd, 3rd, 4th, and 5th if I get on it hard after its been in that gear for a few seconds. If I dumped the clutch from [insert RPM here] it’ll build 10psi instantly. Comes 6,000rpm (full 10psi of boost), _quick shift to 2nd_, WOT…no clutch slippage, but it’ll only build 4psi then slowly creeps up and finally reaches peak 10psi at ~5800rpm. _Quick Shift to 3rd_ and it’ll build ~4psi and max of 6psi by ~5800rpm…and so on for 4th and 5th. If I get it rolling gently, then cruise in second for a bit then go WOT it’ll jump to 10psi and pull hard right away. If I shift into 3rd like a grandma and cruise a bit then go WOT…it’ll build 10psi and pull hard…RIGHT AWAY. Same for 4th and 5th.

Again, 100% positive the clutch isn’t slipping. RPMs arent picking up while speed isnt, and RPM matches speed exactly as it should. And if I dump the clutch when shifting quickly into 2nd it’ll spin the tires…just not build boost.

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**Author:** ![Z31NA2T](https://avatars.discourse-cdn.com/v4/letter/z/e495f1/32.png) [@Z31NA2T](https://forums.speedlife.net/u/Z31NA2T)\
**Post date:** [August 25, 2011, 8:00am UTC](https://forums.speedlife.net/t/wtf-shifting-vs-boost-issue/215836/2 "2011-08-25T08:00:32Z")

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Fixed it, was something stupid. Breather hole on MBC was plugged…

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**Author:** ![Saxon](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@Saxon](https://forums.speedlife.net/u/Saxon)\
**Post date:** [August 25, 2011, 11:01am UTC](https://forums.speedlife.net/t/wtf-shifting-vs-boost-issue/215836/3 "2011-08-25T11:01:48Z")

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i was going to say, sounded like a vacuum/mbc problem

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**Author:** ![Z31NA2T](https://avatars.discourse-cdn.com/v4/letter/z/e495f1/32.png) [@Z31NA2T](https://forums.speedlife.net/u/Z31NA2T)\
**Post date:** [August 25, 2011, 12:29pm UTC](https://forums.speedlife.net/t/wtf-shifting-vs-boost-issue/215836/4 "2011-08-25T12:29:43Z")

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Yupp, I knew it was something stupid. Friends kept saying “are you sure the clutch isnt slipping?? sounds like a boost leak”…but it was actually the lack of the bleeder hole in the MBC holding pressure on the wastegate actuator, making it stay open.