it wont shift into overdrive?

[99w69kitt]

i have a cam/stall/nitrous full bolt on ta 224/224 3500 tsi ssf. one day leaving school going from first to second it shuttered and scared the crap out of me but it was fine. It happened again and know when it trys to go into overdrive it hesitates and doesnt shift i have to leave it in 3rd shifts fine 1st through 3rd but i would like to know whats the problem but am i looking to buy a new tranny? any help will be appriciated.

[99w69kitt]

And if i do need a tranny any body know where i can go in glendale az?

[performabuilt]

You should check out what we have to offer www.performabuilt.com (http://www.performabuilt.com) but before i did anything I would scan for codes and verify the lockup and 4th shift command