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Tap Shift question

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Old Sep 19, 2011 | 01:29 PM
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Default Tap Shift question

I'm wondering if it's normal when in tap shift the transmission doesn't shift into fourth gear? I can shift from 3 to 4 with no rpm change and no overdrive. When the dic says 4 it's still in third gear. When in drive transmission shifts into 4. This is all at highway speed 55+.
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Old Sep 20, 2011 | 05:09 PM
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Nope! Definitely not normal.
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Old Sep 20, 2011 | 06:48 PM
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I didn't think so. I've searched the LS4 threads for something similar to this but didn't have any luck. Transmission seems to be shifting fine when not in tap shift. About 10k miles ago i had a new torque converter installed along with new filter and fluid. It's an '06 with 53k on it. I've also had the stability, traction control and abs warnings come on whenever they feel like it. They will come on one day and the next day it will be fine.
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Old Sep 20, 2011 | 07:16 PM
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hows the battery connections?
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Old Sep 22, 2011 | 09:39 AM
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There is a TSB on the sensor, I had mine replaced about 3 months ago. I lost my 3-2, 2-1 down shift capability in TapShift right before I had the trans replaced. I wish I could get my hands on some solid TapShift drawings/schematics I could probably help more.
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Old Sep 22, 2011 | 11:14 AM
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I just had the car into the GM dealership and they said that when its in tap shift mode it locks out overdrive and gears 1-3 only work in tap shift.
There were codes for my stability, traction control and abs but when i brought it in the warning light wasn't on so they couldn't pinpoint the real problem which i'm guessing its probably the hub assembly? So the next time the warning comes up I need to bring it to the dealer i guess.
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Old Sep 22, 2011 | 11:26 AM
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Locks out overdrive? I'm calling BS on this one. I can shift into 4th just fine. Are you tuned? I can pull a stock 06' GXP tune from HPtuners and look at the shift tables.
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Old Sep 22, 2011 | 12:02 PM
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No tune, completely stock. Going down the higway at 60 mph and shift it to tap shift and it kicks up into 3rd. The DIC says its in 4th? Then i shift from tap to drive and it shifts into 4th. I rarely use tap shift but noticed it the other day.
Thanks for all your help!
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Old Sep 22, 2011 | 04:16 PM
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I checked out you TapShift tables...Check out the attachment, view in paint if it is too small. This is the table that governs your TapShift shift points part throttle. If you were going 60 and shifted in 4th gear it should have shifted...there are 4 -> 3 downshift stipulations but those end at 50 MPH and you would have had to of been on it quite a bit to exceed the TPS %. I'm assuming they put those there to prevent people from going WOT in 4th gear under heavy load which isn't good for the trans.

Could possibly be a shift solenoid, could data log and check certain trans properties to see what is going on internally. Nothing in your tapshift part throttle tables is different from my 08'. GM is full of it!
Attached Thumbnails Tap Shift question-tapshift.jpg  
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