When I'm at WOT in 2nd gear the shifter in 3 at the top seems to slip just before going into 3rd gear .When in overdrive it is fine.

 

how is your reverse? Maybe a cracked sunshell? the sunshell controls your 2nd gear and reverse, might have something to do with it

 

Reverse works great just happends when i'm in 2nd going into 3rd wot. I wonder if my torque converter is locking and before the shift it is unlocking?

 

I was having similar symptoms with my 2nd gear at WOT until it started to get worse and now I have very little 2nd gear at all. The RPM's kind of went nuts right before a noticlble shift in to 3rd. Chuck from FLT asked me to drop the pan and check the 1-2 accumulator piston. It is made of plastice and is commin for them to crack and leak not allowing for a full engagement of 2nd gear. Mine however was not cracked and my fluid was almost black so for me it was not that simple. My 2nd gear clutches are probably shot, so I have a new tranny on the way. My truck does have about 95,000 miles on it so I guess it was due for a new tranny anyway...

 

If you trans fluid was black I'd seriously consider installing a trans fluid cooler with that new trans. 95Kmi isn't really that much.

 

im having the same problem here like it neutralizes before going into 3rd gear

 

You probably have burnt clutches in the 3-4 pack. This pack engage only once in the entire upshift sequence - during the 2-3 shift. For fourth it stays engaged. The 3-4 pack is the weakest set of frictions in the 4L60-E. Once warped from excessive heat there's no turning back. They just get worse.

 

I am getting a new cooler with my FLT tranny. I have only had the truck for a few months so no telling how it was abused before I bought it.

 

Does the manifold pressure switch have anything to do with it?