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USMCRET · 06-06-2023, 03:40 AM

I went to a mechanic last Friday, and he dropped the driveshaft and then put it back on at the end of the day. Driving home, I noted I had a vibration at 40 mph that wasn’t there previously.

Crawling around under the unit, I noted that a carrier bearing wasn’t attached to the frame perfectly square to the driveshaft. Could this be the problem?

twinboat · 06-06-2023, 05:15 AM

Not likely.
Post a few pictures of the slip joint. He may have it out of phase. That causes vibrations.
This explains it.

https://www.moderndriveline.com/a-li...out-vibration/

TandW · 06-06-2023, 05:16 AM

Cause and effect. Somebody did something and now there is a new problem.
The mechanic should have indexed the shaft couplings with match-marks of some sort so that he could reassemble it exactly as it was. Take it back to him if you trust him with a redo.

David 70 · 06-06-2023, 05:20 AM

I don't know if it would cause a vibration but I would want it straight. Did he remove it when he had the driveshaft off? Why was the driveshaft removed?

USMCRET · 06-06-2023, 05:28 AM

Quote:

Originally Posted by TandW

Cause and effect. Somebody did something and now there is a new problem.
The mechanic should have indexed the shaft couplings with match-marks of some sort so that he could reassemble it exactly as it was. Take it back to him if you trust him with a redo.

I’m trying to get some info from him as to exactly what he did, but so far I have not been able to connect with him.

At any rate, it is a three piece shaft and I’m pretty sure he did not disassemble the shaft. It would have been dropped with the carrier bearings remaining attached to the shaft.

I appreciate the input. I’ll update after I talk to the guy.

twinboat · 06-06-2023, 05:49 AM

The other thought is a few needles in a U joint bearing cap are out of place. It happens.

TandW · 06-06-2023, 06:47 AM

Quote:

Originally Posted by USMCRET

I’m trying to get some info from him as to exactly what he did, but so far I have not been able to connect with him.

At any rate, it is a three piece shaft and I’m pretty sure he did not disassemble the shaft. It would have been dropped with the carrier bearings remaining attached to the shaft.

I appreciate the input. I’ll update after I talk to the guy.

If he dropped the shaft as in post #1, he had to separate the couplings.

TandW · 06-06-2023, 06:53 AM

Quote:

Originally Posted by twinboat

The other thought is a few needles in a U joint bearing cap are out of place. It happens.

As the post was in the Sprinter forum we can address the lack of u-joints in most Sprinters. They instead have hard rubber disk flex-joints.

USMCRET · 06-06-2023, 08:02 AM

I think the vibration mystery is solved. I just spoke with the mechanic and found out he removed only the rearward most piece of the shaft. When putting it back together, he only paid attention to the yoke alignment. I’ll bet money that if I rotate that last piece 180 deg, the vibration will be gone.

I really appreciate the responses I’m getting here in this forum. As you can tell, I am a driveshaft neophyte learning as I go. As an example, a week ago I didn’t even know what a yoke was.

jacwjames · 06-06-2023, 08:08 AM

Do a search for Drive Shaft Phasing and it will show you how to make sure the driveshaft is in phase.

On mine the spline shaft has a number of splines so it can be out of alignment but several teeth.

The trick is to get the front and rear Ujoints in phase.

I had my rig towed to Cummins to have radiator replaced. When I picked it up I purposely went out of my way to drive it at interstate speeds for ~40 miles. I immediately felt a vibration, not much but knew something was wrong.

Crawled under the rig and immediately saw that the driveshaft was out of phase. Had to remove U-Joint to fix.

TandW · 06-06-2023, 08:11 AM

It's nice to have someone working on one. Let us know what you find with any splined slip joint. If there is one, make sure it is not dry of lube. I think the couplings are assembled with 6 torx capscrews. In another thread on another forum they need to be replaced with new ones. But that is because of locking compound. I think blue loctite was recommended if you are reusing the original capscrews. Anyway, the coupling halves could be 120 degrees away from the original assembly position. Good luck!

USMCRET · 06-06-2023, 02:56 PM

It turns out that if you turn the engine off with the gearbox in neutral, it shifts it into park. Hence, why I cannot turn the shaft.

The latest wrinkle is I cannot get the slip joint to release in spite of the fact I have taken it apart on three different occasions today. I don’t want to start the engine with the shaft just dangling there. This thing defies everything I believed to be true about drivelines, and for all I know, it will try to turn the shaft when I put in neutral.

I was defeated today. Time for a beer and introspection. Tomorrow is another day.