I have a 1995 Ford E250 3/4 ton cargo van with 176k miles. 3-speed C6 auto transmission, 4.9L L6 engine. The transmission has been slipping every once in awhile when driving uphill between 20-25 mph. By slipping I mean there is a loss in velocity & acceleration and the engine seems to 'race'.. i then let off the gas pedal and just barely accelerate until I make it over that 25 mph mark and it seems fine afterwards. I just changed the fluid, filter, and cleaned the pan out and am still having the problem. The problem seems to get worse once I've been driving for awhile and heat builds up. Are there any sub-components of the drivetrain/transmission assembly I can check out to hopefully 'bandaid' or even possibly fix the problem before it gets worse? Does this problem always lead to complete transmission failure? The driveshaft was just balanced/straightened out and all the splines on the yoke/output shaft are solid. Would appreciate any help here!.. I have haynes & chilton's manuals but please keep in mind im a novice mechanic.
thanks Jay