Jaycajun

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?

Corvette4ever

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

Jaycajun

Yes, At the track and A8 trans in D.

Chazzmania

Has the transmission been tuned?

C7&7

Jaycajun

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.

TurboLX

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.

sevinn

I agree and I'd listen to whatever this guy says. This plus not adding enough lead time to the 1-2 shift for the power.

COALMINER,KY

Mine won’t shift 1 to 2 at all at the track in my 2015 z51 at 699 whp. I have had it to 2 tuners 😡

Jaycajun

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.

COALMINER,KY

Both tuners have tried that and it still doesn’t make a difference !😡

TurboLX

Probably because the TCM is attempting to apply the clutch against the reported torque, which may be significantly different than what is actually being delivered...

COALMINER,KY

How would I fix that ??

sevinn

Properly tuning the ecm side of things such as airflow and torque model.

Jaycajun

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

sevinn

Great to hear. A competent tuner makes all the difference.

BlueDevilZ51

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