Turbo-400 Trans Slips When Cold

[Ol'Jim]

70 Chevelle SS. When the trans is cold/cool, it doesn't want to shift into Reverse for several seconds, sometimes almost 30 sec. Then in Drive, slips/doesn't want to go very well. If you manually shift it into 1st/Low, it immediately starts whining, but will easily drive away. Then you manually upshift to 2nd, and same as in Drive/3rd, the RPM's come up, but not much forward push. (This is all with light throttle settings). If you drive it a few blocks in Low, then it suddenly begins working just fine.
Fluid & filter has been changed regularly/often, I even dropped the valve body, checked all valves, removed accumulator cover, reverse and (I believe) 2nd servo piston. All looks fine, ring is not worn bad at all, springs & balls all there, no varnish. New filter & fluid, even flushed converter.
It was fine, and just kind of started doing this about a month ago. It does get driven fairly regularly, just not a lot of miles. Hate to pull and disassemble/reassemble the entire trans, even more if it still has the same problem. Like I mentioned, it is perfect when warm. Tried adjusting the fluid level up & down a pint at a time: +1, +2, then -1, -2. No change. THe whine is fairly loud in low, but when it warms up and starts acting normal, that sound goes away. Possible front pump? Or an other ideas?
Thanks again! -Dan.

[maxwedge]

Youy have leaking internal seals, only fix is to do an overhaul.

[silicon212]

Second vote for internal seals. It will only do this for so long before it no longer moves.

[Ratt643]

There may be a short term solution, but only short term. Transmedic has an additive that softens the seals. Lucas also has an additive that is more readily available. As I said, this may be a short term solution. An overhaul is inevitable.