Rod_Montana

Howdy. I'm 4700 miles down the road from Montana and currently in Cleveland, TN with a new problem that started after a rough section of I59 north out of Birmingham, AL.

When under compression load, such as coming down a hill in gear (6-speed), I get a vibration in the driveline. Worse the slower you go and in the lower gears. Also does this if you kick it out of gear, but not quite as bad. Under power, all is smooth. In town, its's bad enough to feel like the rumble warning strips on the edge of the highway.

I got underneath last night and shook the driveshaft around. Some small amount of fore-aft play and I can move the center section where it goes through a rubber hung bearing up and down about a quarter inch. Don't know if that's normal. Or not.

I'm sitting in front of Kyle Dodge in Cleveland at the moment, but they're not open and no signs saying they might be on Saturday morning. So I'm thinking of babying this rig into Ashville, NC where I have relatives and finding out on Monday what to do about it..

Hoping to get some hints here thought.

Thanks in advance.

tlloyd

Sounds like U joints or center carrier bearing. Some play 1/4 inch in the carrier bearing is normal because it is mounted in rubber. The permanant fix is a one piece drive shaft "Doghouse diesel performance" you think you have a new truck when you get rid of the carrier bearing.

RAMRODD

Sometimes when a u-joint goes bad you can feel it when you drive it but it wont have anyplay. But they will usually be fairly warm compared to the other u-joints.

gofastman

did you throw a wheel wieght maybe, or worse yet what about lug nuts.
Just an idea to look at.

1985cucv

obvious things to check. tire pressure lug nut tightness, wheel weights, possibly a stuck caliper and the u joints i would bet u joints but its hard to say

Jeff in TD

Mine developed a bad vibration, mostly at very low speed.

Drive shaft and U joints felt tight and looked fine, but when you unbolt the rear yoke from the rear axle and move the shaft around it became very apparent the center U joint only pivots freely one way...

Rod_Montana

A look again in daylight shows some "spattering" of grease around the tunnel over the front U-joint on the rear shaft. It felt old, but who knows.

I slid it out from under the camper and took a drive. Same problems...mainly smooth under power and bad vibes on compression braking, especially in 2nd and 3rd gear. It seems that this might rule out wheel weights and lug nuts, but still worth a look. Thanks for the ideas. Tire pressure is okay, being checked daily, along with the airbags.

I like the idea of testing for heat after a drive. Maybe tomorrow if it doesn't snow.

Got an appointment at the local dealer in Ashville, NC on Monday to take a look.

Wonder if my 7yr/70,000 drivetrain covers this. (63,000 miles).

Dieseljunkie

That's EXACTLY how my truck felt recently. took it to the dealership, and the rubber isolators holding the center carrier bearing in the rear driveshaft were almost ALL torn from the bearing. He said I had 1/2 of one rubber isolator holding everything together. They replaced the isolator under warranty, and all is good. At high speeds, there were no issues, it was at low speeds and when coming to a stop where it felt like all heck was breaking loose LOL.
My $$$ says it could be the carrier bearing in the rear shaft.

Rod_Montana

Almost the same mileage too. Ain't that a coincidence. We'll see on Monday. Hope they have the parts.

Rod_Montana

Twern't the carrier bearing. Was the rear u-joint on the rear shaft. Locked up solid. Only the Cummins 730ft/lb of torque kept things moving forward. I kept having visions of the driveshaft grenading on all those (1000's) of miles while it was buzzing away. First started in Shrevesport, LA.

Plan B was to pick up the pieces. Unbolt what was left and shift into 4wd high until I could find a place with parts.

A few moments of sweat while in the dealership...what if they plug in a scanner? What if they flash the darn thing?

I have Econo-tune Smarty software in there, and the Smarty is a looonnng way away from here.

But not to worry. They wasted no time with that stuff. In the garage as I left for lunch and done before we could finish. Great service. Tate Dodge in Frederick, MD.

Jeff in TD

Yeah, when you said there was only a little play in the center bearing, I figured it was either the middle or rear U joint.

I just got mine put in today. Not real easy. Not too thrilled to have lost one at under 50,000, too.

The transfer case has a slip yoke, so you can't run the thing without the rear driveshaft or it will dump oil...