First time poster, so I'll try to include all the info needed.

Firstly its not an F150, its a '00 Ranger but I don't think that will make too much a difference. It's certianly had it's share of problems(took me 2 months to figure out that the loud clunk i was feeling when coming to a stop and startig from a stop was fixed by pulling apart the slip-yoke on the driveline and greasing it up). Anyway, like i said, its a 2000 Ranger XLT 4.0 4WD auto LS rear end with 136k on it. I had a "pause" between 3->4 so i flushed out the trani(128k, used Valv maxlife atf which I've heard is compatable with merc 5 but i don't know if i believe that), and now about 5k later it has the same pause between 2->3(sometimes lasting over 3 seconds) and has developed a shudder shifting into second. Also at about 55mph under light acceleration it seems like it shifts out of OD and then directly back in so it kinda "bangs", if i step on it so it downshifts then it doesn't.

My questoin is, how do i get rid of the shudder and pause? Do i flush it out and use merc 5 this time? or is the dammage already done and i need a rebuild. Would flushing out the rear dif make any difference(ive heard of a few probs with the LS)?

 

Not only is MERCON V compatible with that trans, it's required. Without it you can get pauses between shifts and shudder.

It might not be too late to fix it by changing back to MERCON V. If it still has the problems, you'll need a rebuild to fix it.

 

If it's a 5R series transmission, it might need a solenoid valve body. Start with the proper fluid and go from there before anything else though.