ok i have a 86 f-150 4x4 aod 5.0 efi, and i am getting a bad vibration under load , realy bad when going up hill and you kick down into passing gear. it does it at about 55 mph when you step on the gas only. it sounds like there is a paint mixer on the roof!!. it has new u joints but that did not help. i also noticed that when the trans down shifts when coasting it almost feels like there is a slight braking effect or a slam into gear. i am stumped, somebody told me its the torque converter, another person told me its either the trans or the tranfer case.i was even told it could be the rear. i dont have the cash to take it to a mechanic, i just put a motor and many many other parts in this thing this year, including a $600.00 towing bill. if it did not say ford on it i would have junked it a long time ago. maybe yall could give me a good starting point as too what you think it might be. thanks

 

First Off Check All Fluids And Make Sure They R Right. I Know My Tranny Was Low On Fluid And When I Would Let Off The Gas It Seemed To Slow Down Because Of The Trans. I Put It In Nutal When I Let Off The Gas And The Problem Went Away. I Put A Quart Of Lucus In There And Toped Her Off Right And It Cleared Up A Lot Better.

 

Check the transmission mounts, they can create vibration under a load....and cause the driveline to bind (tighten up).

 

thanks for the replies, i checked and filled the tranny fluid about a week ago, and that did not help, on the test drive after filling trans a large object flew up and smashed my windshield, that helped take my mind off the vibration for a while . i will check the trans mount and get back asap. i allmost feel like going with a manual trans, but i like the auto. thanks and merry christmas everybody.

 

Vibrations are can be load sensitive but a lot of the times they are not. Are you absolutely sure that your 5.0 is running right? It sounds like you have an engine that is running bad under heavy throttle with a miss and if that is the case it has low vacuum. Auto tranmissions need vacuum to operate properly and without it they can shift very late, and very hard. If you are sure it is running perfect I would check your engine mounts, trans mounts, and t-case mounts. Then I would check for anything else that might have worked its way loose since you pulled the engine out recently. If you don't have any howls or whines, or pinion leaks, it probably isn't the rear end. A Just curious, what tranny is in this truck?

 

hi, i had this vibration with the old motor but it seems to be getting worse now,everything from the old motor was junked except for the intake. so everything is pretty new , it runs like a beast. it has the Auto trans with overdrive in it, it seems to be realy bad when i kick down in to the passing gear uphill. the trans shifts great up thru the gears but when coasting to a stop and it starts down shifting it will start breaking and slamming into gear.it almost feels like a clutch is disengaged because the rpms drop down low then the slamming and breaking effect starts, if i tap the throttle a little bit it will free up. thanks

 

I think you have trans problems. You probably should fix this before it break everything else. What t-case do you have? What rear end? I am guessing that you have a bw 1356 t-case, an 8.8 ford rear end, and an AOD automatic. If this is the case, the BW 1356 is almost bullet proof, the 8.8 probably wouldn't do this without a significant whine, or growl coming from the back end, not to mention it probably would have self destructed by now, and that leaves one thing: your AOD trans. They are known for screwing up. Sounds like it is time for a new one. Just curious, did it start when you serviced the tranny?