Because I know nothing concerning transfer cases and four wheel drive I thought I would ask the question here. I have asked this question on the 1997 forum and have got new info and see what all of you think. 1997 f150 4x4 manual shift. I have had a bad vibration for about three months. I have replaced UV joints and had the Drive shaft balanced. I have a fluid drip which looks to be between transfer case and Transmission. The vibration only occurs when the throttle is on. When you take your foot off the accelerator the vibration goes away. This vibration lasts until about 65mph than it seems to go away. One transmission place said it wasn't transmission one differential place said it wasn't differential. Second transmission place said they felt it was in the transfer case and probably was the bearing between the transfer case and transmission. The estimate is 900 to 1400 to fix the transfer case bearing. Does this sound correct. Thanks for any help.

 

How are the splines on the pinions and is the big nut tight? IF you mean the vibe
happens while on the gas and by that I wonder if you mean neither decel or accel
but just kind of keeping it moving? If that is the case you are just noticing your
driveline harmonic and it is a normal thing you are just a bit sensitive to it or it could
mean some parts are getting a bit loose, Usually around 47 mph neither accel or decel
you can hear a kind of whining vibe type noise the longer the driveline is the louder and
it is normal (unless it is getting louder or changing speed spread)
Take some electrical tape and wrap a few wraps around your front driveshaft and
tie the other end to the frame or a bolt so the driveshaft won't be allowed to spin and
go for a ride and get out and check the tape after you hit 20 mph then drive again and
check it after you hit 30, 40, 50, 60, and see if the sound goes away or anything else.
It should beable to resist the ds from turning if it doesn't do the same for each side
of the front axle shafts and see which one has the parasitic drag on it. You should be
pulling apart and regreasing your front bearings and also lubing the engagemaent parts
with a med-heavy oil (80w90) to keep things lubed up on a regular basis say 30k miles
or so depending on how you off road of course!!

 

When you are applying throttle you have the vibration. When you cost or idle there is not a vibration. I have taken it to three places now and here is the latest. The guy says that the back end of my transmission case is coming loose. He believes that because of the vibration it loosened up the bolts. I haven't seen it yet. The drive shaft was bent and it had been fixed a couple of weeks ago. Although my transmission case may be coming apart my problem is that the vibration has never changed either after the drive shaft was fixed or before it was fixed. To clarify the vibration has been the same from the beginning. So if the case is loose it was coming loose in the beginning and was is the cause of the vibration.