Chevrolet Repair: auto transmission, seal failure, wont move

Question
Hi. Have a 6.2 chevy with auto transmission in a 1994 winni.
Gearbox doesnt make a noise. When running it goes like a train.
When it is cold,put it in reverse and she wont move. blip the throttle a couple of times and she responds. Put it into drive and she hessitates. Blip the thottle and she is fine.
Changed the trans oil and filter and it seems to have made no difference. This has been like it for about a year. It seems to be getting a bit worse every time we use her. 26000 miles on the clock, usual winni seldom usage.
Any thoughts would be great
Many thnaks Ron

Answer
HI RON,,THIS SOUNDS LIKE A INTERNAL LEAKAGE FROM THE CLUTCH DRUM AREA. IT SOUNDS LIKE THERE IS NOT ENOUGH PRESSURE BEING TRANSMITTED TO THE CLUTCH DRUMS CAUSING LOW PRESSURE TO LOCK UP THE CLUTCHES TO ENGAGE THEM. WHEN YOU THROTTLE IT UP IT INCREASES THE PRESSURE ENOUGH TO GET IT MOVING..WHEN YOU CHANGED THE OIL WAS IT CLEAN OR DIRTY ??? WAS THERE ANY MATERIAL IN THE BOTTOM OF THE PAN..IF OIL WAS DIRTY AND LOTS OF MATERIAL IN THE BOTTOM OF THE PAN THIS SOUNDS LIKE WORN OUT CLUTCHES. IF ALL LOOKED CLEAN THEN I AM GOING BACK TO INTERNAL SEAL FAILURE OR POSSIBLY A WEAK FRONT PUMP ASSEMBLY...EITHER WAY THE TRANSMISSION WILL NEED TO BE REMOVED AND OPENED UP TO HAVE A LOOK SEE INSIDE...I KNOW YOU DONT WANT TO HEAR THAT BUT I THINK THAT IS WHAT YOU WILL NEED TO DO IN THE FUTURE..HOPE THIS HELPS YOU TOM..