I am crossposting this from the Aerostar forum in the hopes someone can help.

We just purchased a 91 Aerostar Ext E4WD, automatic w/4.0. It has an intermitent vibration, though vibration is really to gentle a word for it. It is not speed related, but is related to load. And when it happens, it happens only under specific circumstances. If youa re dirving dow the freeway and you completely let off the gas and then gently apply the gas again, theengine will run for a while and then slowdown (fixed throttle and roadspeed) almost as if it were upshifting into OD. BUt it is not going into OD. I believe what it is doing may be locking up the torque converter. For simplicity's sake, lets say that what is happening. Then assuming that, it only vibrates when the TC is locked. Give a stab on the throttle or let off th throttle and then get back on it and the vibration goes away, until the TC locks up again (or whatever is really happening if it isn't the TC). It shakes the dickens out of the whole van, and short of causing it to shift gears or unlock the TC, throttle position does not affect it, other than to make it worse as the load on the drivetrain increases.

Any ideas, suggestions. Is it the TC, or maybe the E4WD? It feels like it is in the front of the car. I am pretty sure it is not an OD issue because I get it even with the trans in D rather than OD.

 

i dont know a whole lot, but thats sounds like the cv joints in the front. but double check my answer with more experienced peoples answers to be sure

 

There were some issues with early Aerostar with 4x4. Take a look at the transfer case and make sure the fluid is ok and full. I've seen a few that leaked and wiped out the transfer case. There was also a recall on early transfer cases and drive shafts. It may have expired though.

 

I have a 92 E4wd 4l, it starts vibrating at 45mph I tap lightly on the brake and it goes away it will come back at increments of 5 or so mph and will go away with a light tap of the brake but will continue with increase of speed or the same speed going away each time I tap on the brake and coming back with the increase of speed or maintaining the same speed, when I reluctantly get on the freeway I'm tap dancing all the way pressing repeatedly to get rid of the vibration or shimmying. it is so bad it's scary and my driving it on the freeway is limited as to what I worked on, what I replaced or a new idea as to what I could do to fix this. I day my engine light came on and it started stalling out when I would stop at a light, but to my delight the vibration went away, come to find out the shimmying unhooked the connection to the maf sensor. I replaced this several times with junkyard parts will try a rebuilt one now and I'll let you know