I took the car out today and tried to do a 30 drop, when the trans usually downshifts to first at about 6200 rpms. It just blew right through the converter and redlined and bounced off the rev limiter. What's the problem? Do I need a whole new trans? Is this common? I know I beat the hell out of my first gear, but damn. My mods are YPT4200, trans go shift kit, trans cooler, deeper pan and TCI flexplate. Help.

 

Scan the event and see. The VCM polls every 1/10 of a second. With that kind of resolution in 1st you can climb your RPM as much as 200RPM/tenth of a second. If you have not got your WOT shift speeds and MPH all lined up correctly that extra tenth of a second is all it takes to pop the limiter.

I scanned mine and used the MPH reading 1 less than the rev point I wanted to shift from. Remember that just because you say to shift at 6250RPM doesnt meant it will. Mine is set to shift at 6250 and actually shifts at 6550.

It takes my tranny 2 tenths of a second to spin 300RPM and 2 tenths of a second to begin pulling down the RPM. I am now looking to decrease the accumulation time for the shift by changing my accumulation springs in the tranny.

With a high-stall like yours the problem is magnified. You would be experiencing more converter turbine lag than a stock one so the RPM transition between Commanded shift and actual shift will likely be higher.

I prefer to shift at MPH than RPM for WOT. It is more stable over time. Thats why you have a WOT RPM and MPH crossover point to play with. At 6000+RPM shift points are critical.

 

sounds like your 2/4 band is shot

1. you can manually shift through the gears and see if it catches all 4
2. autotap it when you are having your problems and log your shifting (gears)

 

I don't have any kind of software though. It just started happening yesterday, so I'm sure something's failing or already failed. Is this usually something that can be easliy fixed, or will I have to buy a complete rebuild? Thanks.