Hi everyone I am new to the forum, I've got a 2003 350 7.3, with the zf6, approx 225000. I've been chasing a vibration that can be felt in the whole truck for quite a while. Feels like a wheel bearing danm near shot. But after replacing both wheel bearings and making over the whole front end it didn't go away. So I replaced the clutch and throw out bearing cause it was getting bad anyway. The vi ration is still there so I checked the harmonic balancer and it was bad so I replaced that. Still no dice. I know that it's coming from the trans, you can hear it in when jacked up and running in gear. Shifts fine in all gears. But the vibration/ clunking is there in all gears and it's getting bad. It feels like a bearing going out. Could it be input shaft bearing or pilot? Thanks for any info I'm on my last leg!!

 

Have you checked your universal joints ?

 

Yes sorry I forgot to mention this, I have replaced ujoints and Carrier bearing. Also when it's running on Jack's there is no vibration coming from rear wheels, diff, or drive line.

 

Does the truck have a Lift Kit installed?

Does the vibration continue to get worse (faster) based on travel speed? Or engine speed?

 

The truck does not have a lift kit. So the vibration that can be felt underfoot is noticed in 1st all the way through 6th, but yes the most noticeable and worst time is when I'm in 6th at 65mph. It seems as if it's because I'm in that gear for a longer period than other gears and at higher rpm, so to answer your question yes I guess it does get worse with higher speeds. It's at higher speeds that a clunking is noticeable randomly. Sorry hard to really describe.

 

Is it a 4x4?

 

Yes it is a 4x4, on that note I pulled the front driveline just to make sure that nothing was actually coming from anywhere​ in thee front end. And that didn't help, I am almost certain that it's coming from the transmission. But the fact that it's present in all gears and just feels like a bearing has me a bit confused, is there what all kind of bearings are in there that would cause so much vibration but not mess with the clutch, gears, or shifting?

 

Pulling the front driveshaft is a start. I would also jack up the front end and make sure both hubs are unlocked. If you have manual hubs, it should be easy to know that by manually checking them. If you have auto hubs, you may have one staying engaged. That could cause your vibration.

 

I know the hubs are unlocked I replaced them with warn lockers last year and they spin freely. So as far as the front end goes it's good. Would it be worth removing rear driveline and running it in gear to be sure it's the tranny?

 

You could also do the reverse and pull the rear drive shaft and drive it in front wheel drive. This will eliminate or pinpoint anything behind the transfer case.

 

You should be able to shift the transfer case in neutral and do the same thing. That would also take the t/case out of the picture too.

This is also a good option to narrow down where to look!

 

Thanks camp springs! So with the electric dash 4x4 **** that does not have a neutral position is there a way to manually switch T case into neutral? I'll play with the switch and see if I can get it into neutral.

 

Probably not! My truck has a manual lever on the floor that has a neutral position. In your case, I don't know if that's an option.

 

There is no neutral position in the electric shift transfer case that is easy to get into. You have to remove the electric shift motor and manually move the shaft to the neutral position and there is no detent to keep it there. One thing you can try is with both shafts off or front and rear wheels off the ground, the trans in gear, not running and transfer case in 4X4 grab both output flanges and rotate them back and forth to see how much play is in the transfer case chain, I have seen a few that had enough play that they caused a lot of vibration and seemed to actually get worse in the higher gears.

 

Thanks for the input! After the last comments I took the front driveline off to eliminate that area. Then the rear driveshaft. With both taken off the truck I put it in gear and ran through all the gears and even in 6th @ 1500 rpm all vibration was not present. So if I spin the rear tires with driveline disconnected the sound is similar to brake pads partially pressed coming from the diff. Hope that makes sense. The wheel bearings in the rear are tight and no play in them. So I removed the drain plug to the diff and there was a grey sludge on the plug itself, noticable shiny particles. Aka not good. Which is strange when I took off the rear diff plate to inspect this spring everything looked good. And also I could not feel anything in the diff before with the driveline connect​Ed in gear. So would worn out diff explain where all this is coming from, ps, changed the fluid in the diff last summer.