so...is it before or after i lock up the converter? does the gear ratio change or what? i put the tci kit into my car so that i throw a switch and lock the converter up. what does the ratio change to? just trying to get the mph figured out cause i know my speedo is off. i would like to know how fast i am going in fourth with the lock up on and 3.73's @2200rpms with a 235/60/15 tire. at 2200rpms with a .7:1 ratio its 65mph

but is .7:1 before or after lock up?

 

It's 0.70 whether it's locked up or not. While it's unlocked you'll have some slippage though.

 

well, when i throw that switch at cruising speeds i get a 200rpm drop...why is that?

just realized i know little to nothing about automatic trannies.

 

Before the TCC locks up, the engine is turning 200 rpm faster than the input shaft of the transmission due to the slippage in the converter.

 

ok...and this helps fuel mileage by lowering the rpms of the engine. and before tcc, my rpms on the engine is 2200 and the input shaft is 2000, but the after tcc, they are both at 2000...is my theory right? so should i base my mph after lockup?

 

Ever seen what happens when you take 2 fans and point them at each other, and turn one on? You know how the second one turns, but not as fast as the first? Well that's how your torque converter works; except it has a clutch that can connect the 2 fans directly together - as if you stuck a stick between the 2 blades.

The gears behind the converter are what they are. They have nothing to do with the lockup clutch. When you engage the clutch, you merely eliminate the "slippage" - like the 2 fans - within the converter. That's why the RPM drops, even though the gearing does not change.

 

Right

 

thanks guys, that's great.