ajsSS

Hey guys I need some input here. My dad's got a 00 SS, heads cam nitrous 12 bolt rear end fully built trans billet yank 36 etc etc. The problem we are having is when racing the car it will not shift into 3rd whether we are on the motor or on nitrous. The car made 440 on the motor and whether we are on the bottle or not it will not shift.. Cruising around it'll shift no problem but when ur racing and u need it to shift it won't, when u lift it'll shift if not it will stay into it till it bangs the limiter. If anybody is familiar with Wally at Trans Magic in Santa Clarita that's who built the trans. The trans only has probably 1500 miles on it. Just trying to figure this out thanks!

mrvedit

Was the PCM tuned for the Yank 3600 converter?
If not, that is the problem. Find a local tuner or contact one of the mail order tuners mentioned on this forum.

performabuilt

iTrader: (25)

Yes as Mentioned kinda sounds tuning related , Many times people fail to understand that the 2-3 shift takes just a bot longer to happen from command to actual shift so not leaving enough room RPM wise they hit the rev limiter with the same setting they have to 1-2 that works fine. I would get tuner to look at command to actual shift times. Where you might get the 4l60e to make the 1-2 in 200 rpm it might take 500 or more depending on power and rear ratio with the 2-3.

mrvedit

^^ Thank you for the good explanation Frank.

Dynamic396

Shift points are commanded based on road speed and not engine rpm. With a loose converter, your engine rpm is going to be higher at a given road speed than it was stock, especially at WOT. The looser the converter, and the more power being applied to it, the more exaggerated this will be.

You need to tune the PCM to command the shifts at a lower road speed in order to get it to complete the shift before hitting the rev limiter. You can also dial up the line pressure to complete the shifts more quickly (if your pump is up to it), especially the 2-3 due to the fact that it's a dual-event shift. Servo travel and 3-4 clutch clearance really come into play here, too.

mrvedit

While mostly correct, the first sentence is technically not entirely correct.
At WOT (typically tuned for 94% throttle), both the tuned MPH *and* the tuned RPM must be reached before the shift occurs.
At less than WOT, there is a shift table which only takes MPH into account. At WOT, there are separate MPH and RPM shift tables.
As mentioned, a high stall converter typically has more slip than the stock converter. Therefore the rev limiter is hit before the shift MPH is reached.
The solution is to reduce the MPH in the WOT table by typically 5% and then blend that into the non-WOT shift table.
The "tune" for a stall converter typically also includes de-sensitizing the misfire table and sometimes disabling some shift solenoid codes.

Dynamic396

Fair enough. Good explanation...