wierd tranny problems

[G-rigged]

We got a 2000 explorer w/ 42,000 miles and recently between 2nd and 3rd gear it will seem lag or hesitate between gears. The rpm's go up and it acts like its not in gear. It only does this for about a second. To me it acts like one of the valves are sticking. It doesnt seem to do it when i take it real easy or when i take it out of overdrive (i know o/d is only the last gear but for some reason it doesnt do it) Im dissapointed this is happining at 42k. Any of you guys hear of something like this ? Thanks

 

[G-rigged]

I found out its torn seperator plate gasket inbetween the transmission and the seperator plate. The guy at the dealorship said this was a common problem but usually with higher milage x's