Hey Barrie, thought I would send this as I don't really want a ton of people giving me crap about what I have in my Jeep, lol. I went with the 513s' after asking a lot of people about them they seemed to be what Teraflex & Moab 4x4 were putting in the most & with the 35" tyres. So now I am finding that they make no difference to power & they make the tranny' change weird. Like it kicks back for a short time & not really enough to do anything before it changes again. I am going to ask them about it b/c maybe' thinking a vaccum leak somewhere?