With the recent release of 4.56 and 4.88 gears from Yukon for 2011^ trucks, I've been playing with the ring and pinion calculator. My question is, the 5th and 6th transmission ratio is .85 and
.67, does this factor in the torque converter locking up? If not, is it a certain amount of rpms for the lockup, or a percentage?

 

When the converter is locked there is nothing to factor. When it's locked the engine speed exactly equals the transmission input speed. It's the same as a manual trans.

If the converter is unlocked a good rule of thumb is to estimate about 10% converter slip.

 

Thanks mark.