Shudder - tap down from 6th to 5th in normal mode

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NEW!!!

I will make one calibration change for an additional $100 per change. For example, changing a shift point for a given gear is $100 vs changing a shift point and a pressure setting would be $200. That value can be used towards the full custom tuning price.

1 post / 0 new

Fri, 06/27/2014 - 22:42

#1

Bill Hooper

Shudder - tap down from 6th to 5th in normal mode

Hi,

2011 CTS-V A6. At 40mph steady state, with the trans in normal mode, tap down to 5th with the left steering wheel button, and the car will downshift to 5th as expected but immediately shudder almost just like limp home mode ... car shudders and stays shuddering under light throttle UNTIL you let up a little on the gas, and then give it a gas again and it is fine. It is 100% repeatable. If you go 45mph, it doesn't do it. If you go 35mph, it doesn't do it.

Now, the exact same thing will happen for 5th to 4th tap down. Exact same conditions to get it to happen Trans tune is stock.

Engine mods are:

ported snout, 2.4" pulley, ported stock tb, ZL1 lid, ice box, headers, high flow cats, borla exhaust, track attack, Air Raid.

Attached is the trans scan for the 5th to 4th version. It happens right at the very end of the scan. Frame 1445, it shifts from 5 to 4. Frame 1484, fuel trims flat line, and right afterward the ignition timing starts wigging out. Frame 1776 we let up slightly on the throttle, and on frame 1780 the fuel trims revive and the car runs normally again, but only when we let up on the gas slightly.

Any ideas?

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Shudder - tap down from 6th to 5th in normal mode

Click on the "SUBSCRIBE" tab to sign up. I will not respond to technical questions unless you are a paid subscriber. Calibration and Config files will not open directly from the site, they must be downloaded to your computer in order to open.

NEW!!!

I will make one calibration change for an additional $100 per change. For example, changing a shift point for a given gear is $100 vs changing a shift point and a pressure setting would be $200. That value can be used towards the full custom tuning price.