what can i do to make it shift to overdrive at full throttle i was looking for a thread to fix this but couldnt find one. also what should be the top speed on 3rd i had my gauges changed and i think speedo might be wrong but top speed on 3rd is like 130something i couldnt stare at it long enough to see exactly as i was going fast and had to pay attention ahead. btw my car is a 305 tpi stock with cherrybomb exhaust

 

What do you mean shift to overdrive at full throttle? Your TV cable runs off the throttle and hydraulic pressure determines what gear you need to be in. If you shift into OD at full throttle you would be running at lower RPM and ultimately making less power than if you were down in 3rd. You will end up in OD(4th) when you need to be.

If you know what gear ratio you have... jack up rear, spin driveshaft and count the number of revolutions for 1 revolution of tire. Put shifter in 3rd gear (1:1 ratio). I think it was something like 70 or 75mph. If you drive 70 or 75 your rpms should equal your gear ratio. So, if you know your tach is correct, you could drive in 3rd until you hit 3250rpm for a 3.25:1 gear ratio. Then compare your speedo to that. It'll get you within 5 I suppose.

Second option is to just drive around until you find one of those construction signs that tell you how fast you are going. While it's probably not perfect, it might as well be within 5mph.

 

yeah everythings fine its just that day when i went like 130 and it was in third and at 5000 rpm it would go into od but it would downshift right away back to 3 unless thats the top speed on the 305 well it doesnt matter i wont be doing that again

 

There is a TV spool/sleeve/spring kit which allows full-throttle OD shifts - Sonnax p/n 77966-94MK among others.