RPM problems.

[Dirtmod66]

2010 Ss L99, SS3 cam, 3.91 gears. Car is tuned the red line at 6900, but will still hit 7800. No spinning on take off(drag). Hits that high in between shifts. What could be the problem?

[ZL1C7]

trans is slipping

[acammer]

Originally Posted by Dirtmod66

2010 Ss L99, SS3 cam, 3.91 gears. Car is tuned the red line at 6900, but will still hit 7800. No spinning on take off(drag). Hits that high in between shifts. What could be the problem?

I'm not sure what the problem is, but I would be willing to bet you don't have the valve-train built for that sort of RPM, so you wanna stay away from that kind of stuff.

New problem, or has been present since it was tuned? If it was fine, and is now having issues after some time without any changes, the trans is probably going away. If it was just tuned and now it's not shifting right, it sounds like the tuner has more work to do.

[ZL1C7]

Very common for the owner/tuner to add more power and forget about the trans. I see it at least once a month at my shop. If you catch it in time the trans might be ok but more times than not the trans has already overheated the clutches.

[FasNuf]

Wait, your redline is 6900 rpm, but your engine is hitting 7800rpm?
If I'm reading that right, your tune isn't set correctly to 6900rpm cutoff.
There's 3 things in a tune that controls engine speed. Spark Cut, Fuel Cut, and ETC Cut. At least one of those should be ENABLED.

[ZL1C7]

Or so it would seem. It will still go over all those limits if the trans is slipping. If you listen very carefully when it shifts at WOT you will hear it on the limiter as it overshoots the rpm shift point. Also very possible that the tuner as the "soft limit" at 7300-7400 and the "hard limit" a couple hundred higher.

[FasNuf]

Have your tuner check your EXTREME CUTOFF.
Engine>Fuel>Cutoff,DFCO>RPM Limits.
The ECM shouldn’t overshoot what’s set here no matter what the trans is doing.
Then have him check the Control Method under the same DFCO tab.

[acammer]

Originally Posted by FasNuf

Have your tuner check your EXTREME CUTOFF.
Engine>Fuel>Cutoff,DFCO>RPM Limits.
The ECM shouldn’t overshoot what’s set here no matter what the trans is doing.
Then have him check the Control Method under the same DFCO tab.

Agree - you can tell the trans never to shift, but the ECM limiter, if configured properly, should catch that.

A soft limiter is something normally reserved only for stick shift cars, as automatic cars don't need to worry so much about bumping the limiter.

The only time you really will overshoot the limiter is if you've got your foot deep in the throttle, you're in gear, near the limiter, and then suddenly remove the load - ie. step on the clutch, driveline failure, auto trans tuning issue, etc. In those instances, the sudden acceleration imparts so much inertia in the engine that it can carry it right out over the limiter set point even with the ECM cutting the power.

The ECM has methods to look for rate of change in RPM, so if you just neutral rev it, you won't typically be able to overshoot so much, but when suddenly released from load at full power, they can zing pretty dramatically. Mostly a problem for stick car guys on aftermarket hydraulics. The ECM watches for clutch pedal movement, but the aftermarket stuff will take the threshold for the release down quite a bit, which reduces the time the PCM has to get out in front of a sudden clutch release.

The noise you hear with automatics shifting at wide open is torque management. Same idea as rev limiting, the ECM is pulling power, usually via ignition timing, to help the trans make the shift without being under as much load. This will kind of sound like a burp, hiccup, or stumble, but it is intentional.

In this case, it sounds like tuning issues may be at fault, but we'll wait to hear a reply from the OP to learn if this is a new problem on an existing setup, or something that has been present since tuning was done.