Blown LT1 A8 slow 1-2 shift
Thread Starter
Pro
Joined: Sep 2012
Posts: 592
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From: Bulverde, TX
Blown LT1 A8 slow 1-2 shift
Built centri LT1 at 800HP has sluggish A8 1-2 shift in all modes {Tour,Track). Stock converter with Vortech V1 blower. 60’ is 1.50s on slicks and trapping 141. Huge lull between 1-2. Once it’s in second it’s great. Is this common and can it be tweaked in a trans tune? Trans is not tuned. So for the C7 blown cars out there did you experience this and were you able to get it corrected?
Last edited by Jaycajun; Apr 3, 2019 at 10:21 PM.
Drifting
Joined: Jun 2000
Posts: 1,577
Likes: 99
From: Dubai, UAE
Is that at WOT only? Are you sure you're not hitting the rev limiter?
I had a similar issue, HPT scan showed that I am hitting the limiter while visually looking at the tacho didn't indicate that
I had a similar issue, HPT scan showed that I am hitting the limiter while visually looking at the tacho didn't indicate that
Last edited by Corvette4ever; Apr 3, 2019 at 03:50 PM.
Thread Starter
Pro
Joined: Sep 2012
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From: Bulverde, TX
The theory is the commanded mph is too high for 1st gear. The supercharged engine climbs the rpm so much quicker than stock, you must command the 1-2 much earlier than stock to avoid the rev limiter.
Pro
Joined: Feb 2003
Posts: 745
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From: Detroit MI
If the trans is having trouble executing, I would be willing to wager that the root cause is actually in the ECM. If your tuner has not properly mapped Dyn_air ant the torque models for the new supercharged combination, it would be no surprise that the TCM has trouble reacting properly.
Safety Car
Joined: Jul 2009
Posts: 3,755
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From: Baton Rouge LA
St. Jude Donor '14, '16
If the trans is having trouble executing, I would be willing to wager that the root cause is actually in the ECM. If your tuner has not properly mapped Dyn_air ant the torque models for the new supercharged combination, it would be no surprise that the TCM has trouble reacting properly.
Last edited by sevinn; Apr 16, 2019 at 04:14 PM.
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Thread Starter
Pro
Joined: Sep 2012
Posts: 592
Likes: 29
From: Bulverde, TX
There is a table in the trans area that has the mph fr the 1-2 shift. It needs to be adjusted, for example, if it's at 34.8 mph, reduce it by 5 mph. The rpm may be at 6,200, reduce it to 5,950. Keep slowly reducing these two items until it shifts better. Ideally you would do it at the track with a laptop and keep tweaking it.
Pro
Joined: Feb 2003
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From: Detroit MI
Thread Starter
Pro
Joined: Sep 2012
Posts: 592
Likes: 29
From: Bulverde, TX
Had trans tuned at the track Friday. Adjusted shift mph and shift point rpms. Dropped 5 tenths off ET, added 2 mph, and shifts perfectly. Thanks to David Human for taking the time to help me out 
Last edited by Jaycajun; Jun 23, 2019 at 01:48 PM.
Melting Slicks
Joined: Oct 2009
Posts: 2,004
Likes: 392
From: Long Island New York
I've been having a very similar issue on my wot 2-3 shifts. Chuck Cow (Corvettes of Westchester) started my tune last week when we met up in my area, he is awesome tuning the A8. I'm getting my trans a fluid flush on the 3rd then bringing it back to Chuck to finish the tune and hopefully correct my poor 2-3 wot shift.( I had the issue before going to COW) So i may have glazed my cluches and hurt my trans from an earlier bad tune from another tuner
Last edited by BlueDevilZ51; Jun 27, 2019 at 07:37 PM.