Vibration at highway speed, indie says driveshaft and U joint?
 

So over the last week or two I've noticed some increasing vibration at highway speed. It comes in regular pulses it seems. At first I thought maybe a tire needed balancing (had to fix-a-flat recently). Brought it to my indie mechanic, he noted that I have two torn axle boots, so says I should replace the axles, but also says the drive shaft and universal joint need replacing. I assume the latter is causing the surging/pulsing vibration? I'm feeling it at highway speed, anything above about 50 MPH, but not much at 30 MPH.

Does the driveshaft/U joint diagnosis sound right?

He's got parts on order, in the mean time, OK to drive? This is my daily driver, so just thinking about taking backroads to work, I don't like the shaking much!

Thanks!

Chuck

Inspect the center bearing first.

I don't think there is a universal joint on a 300D...

Well, there's a U-joint looking connection along the drive shaft about halfway between the flex disks... maybe it is called something else?

Anyway, he mentioned the bearing as well. The axles aren't making any noise, I had one half-shaft replaced about a year ago and it was making a helluva racket.

probably less likely the U-joint, which almost seems to not really need to be there it moves so little, and more likely the carrier bearing or flex discs if its in the shaft. My U-joint had worn a definite flat spot since it stays in pretty much one position during movement, but that was not the source of noise in my drivetrain. Very difficult to check without pulling the shaft down though, since the shaft is anchored like it is, it does not move as easily like a more normal U-joint inspection.

you said you had to fix-a-flat? have you repaired that tire for real yet? They won't be able to balance it for sure with the stuff in the tire.

I don't think you need to "replace the drive shaft" as you said, maybe it was a typo, but if I were you, id get ready for a hefty bill from what it sounds like.

First have your wheels/tyres dynamically balanced.

Next, get under the car and inspect the flex discs. If you have never replaced them, make this something to do soon. Front is pretty damned easy as the driveshaft will compress easily... rear will make you want to punch a baby.

I drop the center support just enough and slide it back for the extra space, do this by removing the heat shield first. Inspect diff mount while in there.

Answer
 

Here is the link you need to read through First.

Driveshaft, Axle & Wheel bearing
http://www.peachparts.com/shopforum/diy-links-parts-category/142402-driveshaft-axle-wheel-bearing.html




Have a great day.

You have one of these two propeller shafts, so you have at least one U-joint.

The rear is easy too if you drop the center carrier down a bit while replacing it.

Thanks folks! Especially for the threads and photos. I'll pass all this along to my indie, though they are pretty MB wise. I like to DIY whenever possible, and I'd try this at home, though I have a sloping driveway, and no garage (near Boston!) so not good for much but oil changes, valve adjustments and a brake job now and then.

I'll make sure they look at the flex discs, I got underneath and didn't see tell-tale "string" hanging off of them. The center carrier piece didn't seem too firm, not sure if it is supposed to be, but lots of play. TooMany, mine is the propeller shaft on the right.

Meanwhile I'm going to stay off of the turnpike... maybe ok to drive on back roads? For what I'm spending at the indie shop I could probably make a down payment on the garage addition. :eek:

In the venue of doing the simple things first, I would replace the axles, as you already know they have one problem. Once that is done, you'll know what other problem(s) you have, if any.

I understand there shouldn't be much play in the center bearing. I can't find any specs for it.

I said that if you read my post fully.

Taking to indie mechanic Monday now that I have the drive shaft and new axles, courtesy Flea Bay. What I notice is that the vibration at highway speed continues even if I drop the transmission in neutral. That makes me wonder if the problem involves the drive shaft at all. Is that a valid test? :confused:

No. Driveshaft will still be spinning, although driven by the tires not the engine.