I thought maybe you guys could provide some help before I head to the shop tuesday.
First of all the tranny has been leaking for several weeks.  I'm keeping fluid in it.  Here's the real issue...when coming to a stop and then accelerating after the stop the tranny slips pretty bad.  It is even worse when turning a corner.  I slow down for the turn, accelerate, and then BAM it finally catches a gear.  Bad slippage or something.
There is also a noise when slowing down that sounds like the noise you have when you put a card, or stick, on your bike so that it hits your spokes.  That's the easiest way to describe it.  Kind of a clicking sound for about 2-3 seconds.  Any help would be greatly appreciated!!
J

How Many Miles on your trucklet ??
When did you last change the fluid and filter ??
Do you know if it is the GM made 3 speed TH180 or 3L30 ??
How often did/do you change the filter/fluid ??

Be honest with your answers if you want my best guess

I have an 89 with an auto, and I have 265,000 Miles
so I know the trans can go the distance.
You might have a bad pump or plugged filter (rare)

Wild

when coming to a stop and then accelerating after the stop the tranny slips pretty bad.  It is even worse when turning a corner.  I slow down for the turn, accelerate, and then BAM it finally catches a gear

Sounds like low fluid.  Have you checked the fluid while running and after it's warmed up (using the "hot" mark)?

Wild,
Honest answers...no real reason to lie about it anyway.
I have 100,300 miles.  Fluid and filter last changed around 87,000 when the solenoid in the tranny had to be replaced by a GM dealer.  I've had it since around 78,000 miles or so.  
I don't know which tranny it is but its a 4 speed (3 with OD?).  

Jerryp,
I've been checking the fluid level due to a persistent leak of late.  I'm keeping it full or at least close to full.  I check it per the manual for a "hot" check, on level ground using the hot mark.
Thanks again for your assistance.
J

I'm not sure if that trans is the 4L30 (TH-200)
or another brand all together, you don't have
any way of knowing how it was treated before
you got it, so there isn't any thing I can scold
you for   , My best guess would be the pump
is bad (low pressure) or the valve body is sticking,
and this could be the dealers fault, left some bolts
loose or somthing else wrong in there.

I don't trust dealers, they always seem to screw
things up, just in my observation here in So. Cal

The dealer mechanics might be really good there.

You could try a transmission flush, or a treatment,
I had a bad neutral drop feeling situation, stop from
freeway driving, stop and look hit the gas to go and
rev-bang into gear, did it since it was new. I got a
bottle of Slick50 Auto Transmission treatment, and
it never did it again, this was at 75,000 miles after
I changed the fluid I put this in, and it's been good
since then, almost 200,000 miles ago.

I don't think it's worn rebuild time, but it could be
another mechanical problem, I would not expect
it to be too expensive, but you know how trans
rebuild shops charge, personally I would not go
to AAMCO, just bad service and stuff (friends trans)

Good Luck, I hope it's minor

Wild

Another thing you might want to check is the vacuum modulator itself and the lines heading up to the manifold.  Usually, there's a rubber line at the modulator and at the manifold and a solid line in between.

Just checked your sig.  I guess I should say, check the modulator if you have one.  Old ones like mine used vacuum to help determine shift points, yours may be all computer controlled.