Odd issue
 

So I've had my truck for about 6 months now and have been fixing all the half assed repairs on it and I've been playing with the afc, and I've noticed that if I'm at WOT for a period of time my truck seems like it kicks out of gear(auto) and just revs untill I let off and let it re-group.

It's for this reason I am holding off on putting 4k springs in.

Any ideas guys?

Have you checked trans fluid level or changed the filter at all? Sounds like its having a fluid starvation issue and it cant suck up enough fluid to keep the pressure up on the clutches and bands, letting it slip. We had a Dakota at work that would do that when the filter got dirty, and a 24v dually that would just slip if you mashed on it but light throttle it drove normally, the front pump of the trans was out. Being a 98 you should be able to put a scanner on it and watch the pressures on it to see whats going on.

Thats probably the first place to look!