Manual Transmission T56 | T5 | MN12 | Clutches | Hydraulics | Shifters

locked out of 3rd gear

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Old Aug 20, 2008 | 11:04 PM
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Default locked out of 3rd gear

I just got back from the track and am baffled. every time i try to shift into 3rd at redline, it "locks" me out of 3rd until i let off and the rpms drop then it lets me go in just fine. any guesses what is wrong? it does the same thing on the street. I have a built tranny with a pro 5.0
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Old Aug 21, 2008 | 12:00 AM
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Its prolly this(from the Manual Trans FAQ sticky) :

To sum it up, basically GM didn’t think things through all the way when selecting the hydraulic lines for your T56. The steel braided line that plugs into the master cylinder has a tiny, tiny hole in it, which causes unnecessary restriction. During a quick, high-rpm shift, fluid cannot get where it needs to go fast enough, so basically it will feel like you are shifting without a clutch. It may be difficult or impossible to shift into 2nd or 3rd, and you may have some problems with the pedal itself.

When performing the drill mod, you remove the master cylinder, separate the line from the cylinder, and drill it out. To visit a site with full information and pictures, click HERE. It will be listed under the Transmission section, along with the adjustable master cylinder install (although you can do the drill mod without changing the master).
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Old Aug 21, 2008 | 08:10 AM
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I already have a ls7 clutch, pressure plate, ls2 flywheel, and new slave cylinder. I also have the drill mod done. thanks for the reply though
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Old Aug 21, 2008 | 09:07 AM
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check for clutch drag, though not sure why that would affect only 3rd.. How many passes on the built trans, and how many missed 3rd gear shifts? Could be that the blocker is just worn enough that it can't effectively synchronize 3rd at higher RPMs.

Do you downshift often on the street, without rev-matching?

Last edited by 85MikeTPI; Aug 21, 2008 at 02:08 PM.
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Old Aug 21, 2008 | 01:55 PM
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Originally Posted by stealth1281
I already have a ls7 clutch, pressure plate, ls2 flywheel, and new slave cylinder. I also have the drill mod done. thanks for the reply though
Oh. Never mind then lol. Good luck.
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Old Aug 21, 2008 | 09:12 PM
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What fluid are you using in it ?
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Old Aug 24, 2008 | 11:34 PM
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Originally Posted by 85MikeTPI
check for clutch drag, though not sure why that would affect only 3rd.. How many passes on the built trans, and how many missed 3rd gear shifts? Could be that the blocker is just worn enough that it can't effectively synchronize 3rd at higher RPMs.

Do you downshift often on the street, without rev-matching?

I'm not sure how many passes were made on the transmission before I bought it but i have 2 passes on it at the track and probably 4 or so on the street trying to figure out why it won't allow me to go into 3rd at high rpms. so, to answer your question, around 6. same result every time.
not to sound stupid, but what exactly is the blocker?

Whenever I significantly downshift on the street, i always rev match
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Old Aug 24, 2008 | 11:36 PM
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Originally Posted by thesource
What fluid are you using in it ?

can't think of what they used. what do you recommend?
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