I was reading in another thread about switching to a carb engine and read something about the torque converter lock-up. This may be a dumb question but just curious what this does. I bought my 90rs and it had already been switched from a TBI 305 to a Carbed 350. This guy seemed to not know everything about swapping engines so I was curious if this is something I need to look into....

A torque converter basically is a fluid coupler between the engine and transmission. There is always some "slip", difference between the speed of the engine and input shaft of the transmission. The fluid absorbs heat in this process, and heat is energy, and power is energy. So, this slip represents a loss of power that the engine is creating, and therefore efficiency.

The torque converter clutch simply locks the input to the output of the converter during cruise conditions, thereby reducing the heat generated and transferring more of the energy produced by the engine to the wheels to move the vehicle.

With regard to the TH700R-4, the transmission was designed assuming the torque converter clutch operates. If the lock-up function isn't working, more heat gets into the works of the transmission, particularly the 3-4 clutch pack. While the transmission may seem to operate okay, it is slowly being killed.

Alright,
So since i'm going to be doing a rebuild in the next month, is there something I should look for to make sure that this was done correctly when the engine was swapped the first time?