hardtarget870

I have a vibration at about 40-45mph. Both on and off the go pedal on flat ground. I have found and read many threads pointing to the rear most u-joint and/or all u-joints. I was sure this was my problem but when I took the 4 bolts out of the flange and lowered the drive shaft I found no play. The only thing I found odd is the stiffness of my 48000 mile rear u-joint. It does not give to the weight of the flange in either direction. I can move it by hand but not the loose feeling I remember as a kid helping Dad change u-joints. I have only called them bad for having play, never for stiff. Am I looking in the right direction? Carrier looks okay, no deformation of the rubber, shimmed the same since the lift install 35000 miles ago. I have also been reading all of the one piece drive line threads too. Is that an option for 5" lift? Sorry for the long post.

P.S. you guys and gals make this a great site. Thanks

cincydiesel

I just took my rear shaft off Monday to replace my front U-Joint. My rear flange would only move by hand or under its own weight while setting on the ground. I would not be worried. The if the joints are that loose then they need replaced.

hardtarget870

Thanks Cincydiesel.
The vibration is real hard to pin point, feels almost like running over shudder strips, or loose lug nuts. It gives anyone who rides in it the sense that something is wrong with the truck or something is about to fall apart.

Hvytrkmech

U-joints should move freely, if it has to be man handled to move it is junk, change it. The stiffness is the precursor to the excessive play. The u-joint is actually starting to seize up, then it starts to throw rust out of it then fails very rapidly.

My truck has just started to exhibit the very same symptoms you described, in the next week or two all the u-joints will be replaced and the entire driveline will be sent out for balancing.

BigWhiteTruck

I agree if the joint is stiff it is bad. U joint vibration will crack the overdrive unit of the trans if left to long.

hardtarget870

Sounds like I need to pull the whole drive line and replace all joints, and have them check balance just for safe measure. I definitely dont want to mess up that overdrive housing, my wife is letting my pull the trigger on a full Goerend in the next month or so, I need the full core value.
Thanks BigWhite for the warning. HvyTrkMech, please let us know if your symptoms go away when you replace your u-joints. I will probably pull the whole shaft this weekend and at least replace the joints, I will have to look around to find a good driveline shop. I will update with what I find.

Hvytrkmech

I will do an update after it is completed. I am also going to have the front shaft balanced, I will update on that also.

hardtarget870

Update - still have vibe.

Pulled rear drive shaft and replaced only rear most u-joint. Really it did not need it but I wanted to wrestle that plastic-bound u-joint cap. What a pain! Also checked the carrier while I had it out and it looked good. Put it back in the truck and mounted an old 8mm video camera uner the truck on the trans cross member facing rear so you can see the carrier on back. everything was silky smooth from the carrier on back. So I turned the camera around and went for another spin. When I feel the vibe, the transfer case is oscillating. The video was shot behind the transfer case on the drivers frame rail pointing at the front driveshaft. So only half of the transfer case is in the picture but exactly when I feel the vibe, the transfer case is bouncing around.

What would make the transfer case bounce around like that?

My next plan of attack is to take the front DS out and drive around like that.

Could that large harmonic balancer thing on the front of the rear DS cause that problem? It is not loose or anything so it is still in the factory position.

Maybe one piece rear DS?

Also seen on video, same vibration on takeoff from dead stop, but only 2 or 3 bounces then smoothes out until about 42 mph the bounce resumes.

Will work on getting video on computer.