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.

Thanks, Kerry.

Those things may well need replacing..
but I would sure check the tires first...
Having someone drive your car and you drive beside them to see if anything is jumping around is a fast easy test...

That's a great idea. I'll probably have to be the driver, my wife won't get behind the wheel on this one. The other thing that is worth noting is that the vibration isn't really constant, it kind of has a surge/beat to it. I suppose unbalanced tires could oscillate like that.

This sounds exactly like the problem I am having with my car. It has the same things going on.

me too. i feel it in the seat it seems and in the steering wheel too. but it only occurs at speeds over 50mph. i don't feel it at all under that speed. i was thinking the flex discs?

Hey Markho -- that is pretty much what I experience. It's kind of a pulsing shake/vibration. I did a superficial inspection of the flex disks but not sure I would recognize whether they need replacing. Anyway, I do have a new drive shaft that has flex disks as well, so hopefully it will do the trick. I will report back after next week's car shop visit. I figure it will involve a rental, since the '82 300D is my daily driver.

-Chuck

How long since the tappets were set? I know it sounds crazy but a too tight tappet will cause the valve to float and not seal. That will create a vibration at the speeds you indicate. In my case,coasting in natural the vibration disappeared.

My indy said it was the flex plate, pulled the trani to check, the plate was OK. THEN he said to check the tappet clearance. Two valves were 000. Got them set just in time to avoid burning the seats.

So the good news is that between parts and labor, I'm only looking at about $620. Got the parts from eBay and the labor was just over $300 to have the axles and drive shaft installed. Good, right?

The bad news is that I'm still experiencing vibration. Here's the "duh!" part of the story. One tire has fix-a-flat in it.

I needed those parts replaced anyway, yes I did. :)

You still haven't balanced your tires yet?
The first thing I thought of when I read the topic of this post was tires. I can't believe you haven't checked that since it was brought up a few times already.


Danny

Actually I had that done first thing, but I'm back to it now. I was thinking that the fix-a-flat gunk may not allow proper balancing, since it is liquid and sloshes around. Kind of like the ol' water in the tire trick.

That fix a flat stuff, while effective, really stinks to fully remove.

Even if they repaired the tire by removing it from the rim and properly patching it, if they did not soak all the liquid out of the tire, even a little bit can still cause an imbalance. I absolutely hated sopping the milk up, and washing the inside of the tire out and drying it so my abrasive disc for proper patch application would actually cut the rubber.

The fix a flat lubes tire cutting tools right up and you can cant get a good cut.

I would check the tire in question to see if they plugged it from the outside, or patched it from the inside.

If you wan't to verify without spending money, just move the tire around the car. if its one tire, the vibration will change from felt through the steering on the front to through the body on the rear, if felt at that point.

I hope you kept the original drive shaft, they don't really go bad unless they are broken or bent or something. they can be rebalanced for reasonable cost, and the U-joint can be replaced as well pretty easy when its out of the car. Might be useful for someone or yourself later on, it sounds like it was not the problem.

Just a follow-up. Replaced tires on rear. I wouldn't have thought that an unbalanced rear tire would make so much vibration, but it sure did. My indie has the old drive shaft, as I don't have any garage. The neighbors don't much go for that stuff in the front yard:(

Still was good to get the new hardware (two new axles and new driveshaft) all is much smoother. BTW, got those Fleabay axles for about $70 each, we'll see how they wear.

Now still to forever troubleshoot that vacuum system.

Thanks again to all for your help and thoughts on this.

When I was younger & didnt have much storage space, I used to put things in the ceiling cavity. Just had to make sure heavy stuff was placed over the walls.