Transmission problem

Help me please !!!!!!!!!!!!!!
I purchased a rebuilt th 350 from what was supposed a reputable
local tranny shop. It came with a mild shift kit installed. I installed
the 350 as I had done many times before, with a 1200 rpm stall
converter. It ran great for about 3 months. Now, it has no forward
gears, it grabs reverse very well. I tried to hit up the tranny shop
on the 3yr./ 36000 mile warranty. He had gone out of bussiness
and dissapeared. I have pulled the pan - no significant debris and filter is clean. I should also mention that with fluid at correct level,
it spits a large amount of fluid out of tranny dipstick tube.

Any ideas ????

I suspect some dirt or debris has gotten into the valve body and is allowing a valve to hang open, so its dumping the forward drum fluid pressure, instead of directing it to the drum.
It may be an idea to remove the valve body, carefully disassemble it and clean it throughly. Use clean cloths and spray cans of brake cleaner.
Make sure you reassemble it exactly the way you take it apart, keeep and eye out for broken springs and valves and use a new gasket when you bolt the valve body back to the trans.

As for the dipstick, maybe someone can correct me on this, but I recall these trans have a vent..........either a little tube on the top of the housing, or a vent in the bellhousing???????
If the vent is blocked, it might push the fluid through the dipstick tube, but this is just a guess on my part.
Another guess..........the trans is not overheating is it? You have a good cooler with good flow, yes?