I need help diagnosing my tranny problem. I replaced the filter modulator and converter but it still slips going from park to 1st. any help would be apprieciated.

 

Does it slip if you go directly to low?

 

It does. It slips from any gear if I'm putting into 1st. And it slips when taking it out of park regardless of the gear I'm putting it into. But it only slips after my truck has been sitting for about 5 or more hours. Other than that, 2nd, 3rd and reverse are fine. Do you think it could be the fluid pump?

 

No, I don't think so because oil pressure affects all the speeds. The only thing in common with all the forward speeds is the forward clutch in the trans.
Have you tried to start the truck after setting the 5 + hours and run the engine for a minute or two and then shift into gear and see if you still have the problem?

 

You probably have convertor drain back.

That's when the fluid drains out of the convertor into the oil pan and it takes a few seconds to refill the convertor.

Pull the valve body and check for a blown gasket and sticking valves.

 

I agree with you stuart40ca commonly known as bleed back valve its probably sticking

 

It does sound like it could be converter drain back. The simple test is to run the vehicle for a few minutes then put it into gear. If the problem is not present, then that would confirm it.
Unfortunately , the valve is located in the pump body and you would need to remove the trans and remove the front pump assy. It's easier to give the truck a minute to warm up and fill the converter .