can someone expain what the stall speed means? and differance between lockup &non-lockup,and also can anyone recommend a good torque converter for my truck(stall speed),89 f250 with 5.8 and c6, mainly around town driving, and boat towing,

 

A stall speed is the highest RPM the converter will allow your engine to turn at without turning the wheels, i.e. if you put it in drive and stood on the brakes and then gave it a lot of throttle, how many RPM the engine can still turn at without moving the truck. The idea behind a stall speed is to allow the engine to get turning at an optimal RPM where it's producing good power and will move the vehicle with no problem, much as you would bring RPM up before letting off the clutch in a stick shift rather than dropping the clutch at idle. The proper RPM for a stall depends on the cam in the engine and what RPM range it's producing the power at. For a stock engine, keep the stock converter. It's already set up optimally for that engine. If you go to a more high performance cam it will tend to make power at a higher RPM and will require a higher stall to work properly (cam specs will typically suggest a stall range). High stalls tend to build a lot of heat in the tranny and a lot of times will slip excessively while driven in town because your operating RPM doesn't meet the stall speed. Which in turn means more fuel comsumption, more tranny heat, etc.

Converters "slip" since they are basically a turbine driven with fluid. Lockup converters use a clutch system more or less which is typically controlled electronically. When the truck is at a cruising RPM the lockup engages so there's no sliping in the converter, thus reducing the engine RPM, great for fuel efficiency. There is no lockup converter available for a C6, they will typically slip about 300 rpm at cruise.