odd new vibration

[fuzzydog]

91 F250 7.3 non-turbo, zf5 - bone stock 348000kms

bought this truck a couple months ago and was told it was well maintained and I do believe that to be true. whatever has happened is coincidence.

On a long road trip this past weekend I developed a wierd low speed vibration that presents itself after the clutch is fully engaged. vibrates the box and the truck seems to bounce a bit, almost as if tires were oval (tires are newer winters and truck is aligned). smooths out around 45-60kms/hr then vibrates again to about 80kmh and is actually quite smooth at freeway speed of 100kmh. Also, there is a gear buzzing noise in 5th at freeway speeds but it is not severe. I just attribute to a trans with 348000kms on it

I had read about the DMF clutches (which I believe is what is in there) but would it act like this or is it more of a constant vibration? The clutch was changed sometime in the last couple years.

Unfortunately when I got back from my trip it was wet and snowy here so can't (don't want to) crawl underneath to check u joints and such. I'm pretty sure a u joint would have blown up by now because I did over 500kms of mountainous hwy driving since it started, and it hasn't gotten worse.

Any BTDT experiences and suggestions as to what to look for?

Is there any sort of inspection plate for the clutch?

 

[BigRigTech]

Maybe you have a bad trans or engine mount - it will do the same thing.

 

[fuzzydog]

Maybe you have a bad trans or engine mount - it will do the same thing.

That could make a whole lot of sense - will def check it out.

One other thing I uncovered yesterday is I coasted down a hill in neutral from 0 to about 60kmh and the ride was very smooth (even with front hubs locked) so its not in the running gear. I will check out the motor and trans mounts as well as driveshaft ujoints

 

[Andrew M. Frankli]

Check your U'joints as well - I have seen cases where they are quiet at certain speeds, but at other speeds make the truck feel like it is going to rattle into pieces. On mine, I pulled the propeller shaft off and found one U-joint with NO needle bearings left - just brown sandy dust. Yet this thing was fairly quiet at highway speeds!!

 

[suv7734]

+1 on the u-joints. I had a vibration that was getting worse and worse. The u-joints were all tight, the pinion yoke was tight etc etc. I finally decided to pull the driveshaft out to check the carrier bearing and joints. This is what the u-joint at the carrier looked like The needles were still intact and it wasn't making any noise but it sure shook the truck at certain speeds.

 

[fuzzydog]

+1 on the u-joints. I had a vibration that was getting worse and worse. The u-joints were all tight, the pinion yoke was tight etc etc. I finally decided to pull the driveshaft out to check the carrier bearing and joints. This is what the u-joint at the carrier looked like The needles were still intact and it wasn't making any noise but it sure shook the truck at certain speeds.

hmmm... that looks like one of those new-fangled splined u joints

 

[suv7734]

hmmm... that looks like one of those new-fangled splined u joints

And it only has about 300,000 km on it too ;p