Transmission problems

two days ago i've go problem on my Pontiac Trans Sport 98. In the morning start car, shift to (D), car is not moving, shift to (3) - same thing, then to (2) car start to move slowly, then (1) - runs OK, then get back to (D) - runs perfect. Turn off engine, start again put on (D) - runs perfect. Drive to my office. Park the car for a day. When finish my job after 10 hours. Start the car put on (D) - not moving, then jut put on (1) for 2 seconds, and even did't run 1 inch, get back to (D) - runs perfect.
Next morning start the car, put on (D) - runs perfect - all day.
Today morning- start the car, put on (D) - not moving, put on (1) and then back to (D) - runs perfect.

checked level in transm. - OK
had changed transm. oil 5-6 monts ago.

went to first shop to ask what to do... they tol me need to rebuild transmission - $1400, to fix problem (no warranty) - $700

may somebody know these things ? is it a major problem or not ?
is it worth to pay 700 for repair or 1400 for rebuild ? Thanx, Tim

Eh...I can just go by the book...it suggests that such behaviour can be caused by damaged o-rings, damaged seals or stuck control valve, you pick your choice. If first 2, this condition would probably worsen with time, so unless you are really caught with requiring full reliability, I'd wait for the fact to confirm. Using Low range modifies somewhat the oil circuit and can dislodge a sticky part..thus return to normal drive operation afterwards.
One very easy and inexpensive thing to do is remove the trnasmission oil pan - and all the oil with it of course - and change the transmission filter and fluid. If some abuse of the transmission occured -like hauling heavy trailers - then filter clogging might also be an explanation - I have had that condition long ago with another make. Emptying the torque converter completely may require some extra tricks - but it would not "make or break" the improvement if there was one to be. Be sure to use gm type transmission fluid.

..of course, since you have had new oil -and probably filter - 6 months ago, then abuse should have occured in the last 6 months. Otherwise, disregard the suggestion.

i've change oil but never change filter... if just filter i think i can do it my self... i think filter in Autozone gonna be about 25-40 buks in cost
i've just called some "transmission repair shop" they told me they have some special computer to check what's wrong inside transmission without taking it off... is it for real ??? or that just commercial trick...

well...I'd take that lightly but in any case, the trouble would have to be there all the time for proper diagnostic to be done, so...as long as it reverts to normal operation, diagnostic is doubtful, and if trouble is permanent....then you do not need diagnostic...you need a repair job....

i just went to Auto lube shop were i had my "transmission flush" in may, they told me they didn't change the filter then... so they gave me discount and for 39.99 i've got transmission oil and filter change in additional they put some "Transmission Fix" wich making transmission oil more stable and fixing slipping problem... well... we'll see tomorrow morning...
Another thing, when they puled down transmission oil pan... there was verry clean, no metal dust or small parts (like i have seen before in my other car)... and the guy told me that it looks almost perfect from there... so i don't have any other choice - just to wait...

GOod deal..

a good guess would be the foreward roller clutch "is" failing in the trans
shifting to low allows a band to apply which reinforces the roller clutch,,,thus it will move......but the problem's not going away!!!

This morning:
start the car, put on (D) - push on gas - slipping, with vibration (wasn't before), wait 30-40 seconds - push on gas - start moving, ride around the block, runs good....so, something hapend after changinh filter, oil and adding that special "treatment", i can't tell that problem is gone, becouse still slipping at the start, but fact is that what i did esterday, affected that broken part, or parts in transmission to act different...

This would also concur with trannyman52's guess. That one way clutch - also known as sprag clutch - may be damaged and having changed the oil quality might give it some grip. This clutch has to withstand the initial "thump" , I think, when shifting from neutral to forward so be careful not to rev up the engine while shifting...because if this is indeed the culprit, the extra "thump" might be the last...

and if this is that sprag clutch - how difficult is to fix it - is it total rebuilding of transmission or something less expensive... ?

Transmission must be taken off car and "dismantled". Car is not old, and you say oil was clean so clutches and bands are probably in good shape. A bad "shift in" may have damaged the one way clutch only...so discarding the whole set of disks - there are a lot ..might not be required but most transmission repair shops would not garantee the work unless they inspect and change everything to mint condition--and I understand them. For myself, if one component was positively identified as the problem, I'd stop there.
BUt wait a little....it might give you a break

thank you guy's a lot...
i'm thinking if transmission needs to be rebuild anyway... so probably lets wait and see...
another think, looks like i need to start to look around... to find somebody i can trust to rebuild trans. after it stops... if you know anybody in brooklyn or around new york or even new jersey, whose not so expensive and a professional to do this kind of job... let me know... thanx