Bill89f1504x4

Hi All!
Hoping someone can help me with this one...it has me stumped.

I have an 89 F150 4wd rebuilt 302 5spd manual.
New ball joints 1.5 yrs ago, new brakes, new wheel bearings and seals, new rear driveshaft u joints.

Very recently while driving down the straight level highway in 2wd, hubs unlocked, she starts to make a terrible grinding noise with a vibration. Kicks in at around 90kph/55mph and it is pretty intense.
Changed front wheel bearings and seals both sides and no joy.
Had wheels balanced 2 yrs ago and no off-roading.
Took it to a garage 2x, different mechanics...couldn't tell me much more than that it's coming from the front.

Any ideas?

Thanks!

93mudder

does it do the same with the hubs locked in? and I've also seen the hubs somehow to tight and can half engage the axle and that can cause the grinding and vibration.

Bill89f1504x4

Hi 93mudder - I'll give that a try and see.
I did try it in 4wd with the hubs unlocked and still the same symptoms.
I'm thinking tomorrow night I'm going to try a couple of things:
- lifting up the rear end and get the wheels going at highway speed to see if it's still there
- taking out the driveshaft and trying it out in 4wd with only the front wheels engaged (hopefully that doesn't wreck anything)
I'm thinking I can eliminate a few things with these tests... Been trying to work this one out for a while :s

Bill89f1504x4

Well...I skipped a few steps and learned something.
Took out the driveshaft and ran her up to what is usually 'horrible vibration speed' and ...no vibration or grinding noise!
This driveshaft has its second set of new u-joints on it and they both turn smoothly...should I assume the driveshaft is pooched?

Bill89f1504x4

Going to close this off.. Issue was a combination of pooched driveshaft causing a vibration with the exhaust against a frame bolt. All sorted.

Domingo Pimentel