While driving on the freeway the other day. I noticed every few seconds te rpms would go up by a couple of hundred, the they would drop back down. Is it the overdrive or converter? And what could be the cause of this, it's really annoying. Thanks for all of your help.

 

more details needed on your car, year and mods?

 

Yes I should have added that to my 1st post. It's a 1996 4.6 GT all stock except for flowmasters.

 

I shouls also add that it's always shifted rather hard. And it does shudder somewhat when going to overdrive or converter lockup.