LS2 vette - mystery stall?

[ho52806]

My tune is near done. (232/236 .595/.595, 3200 stall, 3.73) I have tuned VE, MAF, my PE, transmission and the car runs awesome! From part throttle to WOT the car is sickenly fast. Sometimes scary on a downshift! I have virtually figured out all the bugs except one.

When coasting down from zero throttle from 50 mph down to about 40 mph, my trans is set to downshift from 4th to 3rd at 47 mph. Well the car seems to just barely pass 47 and hold 2500 rpm then just as it passes 47 to 46 or 45 the tach just drops suddenly to about 200 rpm and catches. Then 3rd will come in and bring it back up to about a 1000 rpm. If I come to a rapid stop, then it may stall all together - very, very dangerous!

Now I have tuned base airflow for all forward gears. I have literally re-logged and re-finessed the base airflow at least 15 times (today only) for 3rd gear and 4th gear. I don't think i can get it any better. I have also looked at coast timing and turned it up 2 degrees in which I got cruise control at 30 mph then backed off 1 degree above stock and the mystery stall is a hair better.

Could it be a TCC engage or release problem? Or is it engine related? I have tried changing many things and have re flashed almost 20 times today.

Does anyone have any ideas? By the way the other gears downshift fine.

[gman4dx266]

Idk, id check the tcc tables first...sounds like it might be still locked (like leaving the clutch out but coming to a stop with just brakes). Post your file though.(and a scan too, if you have one)

[ho52806]

Ok. I've noticed that my TCC has the 4th release set at 40 mph. I have worked w/ every table of engine and trans except this one. I have left all the TCC stock. As for trans shift patterns they are set fairly aggressively - all the same as far as norm, perf, cruise, hot.

Here's my tune. I'm not sure if I can get the log to go through. It says saving as a histogram? I've tried to figure it out but all I can get is this .hpl file.

If it is the TCC locking up, is it that easy to just set the 4 release for above 48 ish? Also, since I have late shift points, should all the applies and releases be bumped up?

I'd like to understand how the TCC engage release works - not just plug in #'s randomly.