hey guys i got a 350 engine, 700r4 tranny, and a 100 shot of nitrous. when i hit the bottle it shifts fine until i hit around 3rd gear it gets up to 5500rpm and i kill the shot and the pedal. how come it wont shift into fourth? i put the b&m tranny valve in it awhile back to help it shift into o.d while full throttle. is my tv cable to loose or to tight? or am i lookn at another issue?

Do you have a shift kit?

no stock tranny. should i put a kit in it? if so what kind

Are you 100% sure it doesnt have a shift kit? cause thats one of the main reasons as to why it wont shift. It's all read in the ecu and crap to keep it from shifting when at full throttle to prevent hurting the transmission. Also a shift kit wont help the shifting from 3rd to 4th. It only helps the shift firmness and crap from 1st to 2nd to 3rd i believe. If you get one go with the Trans Go brand because it doesnt beat the brains out of your tranny like a B&M will. It's all in the throttle with a Trans Go. More throttle means the firmer the shift will be. A B&M shifts hard even when cruising and babying the throttle. One other upgrade you can do while putting a shift kit is installing a corvette servo which runs roughly around $20. The only thing I can think of thats preventing your 3rd to 4th shift is a shift kit, worn out servo, or possibly a worn out band inside the housing.

The nitrous should not affect the trans shifting.

As you probably know the 700 won't shift to forth at over 70% throttle. The "tranny valve" you mentioned, is it the valve to allow full throttle fourth gear upshifts? Was it installed correctly? If so then you have a different problem. Check the TV adjustment. Make sure everything is moving properly at the TB (or carb) and in the trans. You can pull the pan to make sure the cable is actuall moving the valve inside.

Does it ever shift to fourth? Are you in "OD" when it refuses to shift?