Rear Axle / Drivetrain clunk

Thought I put this out here and share some experiences.

I've bought a dirt cheap 02 sprinter 3 years back and had it as kind of a rolling project.
The list of small and slightly larger issues was several pages when I got it. Now its just one thing left bothering me;

The clunking in the rear axle (probably)
At first it was there everytime I was a bit sudden when releasing the clutch when changing gears, from stand still to moving and from decelerating to accelerating.

So i checked the gearbox mount. (cheap part so I replaced it anyway)
I've checked to driveshaft, no slack.
Replaced the differential oil and removed the cover to check the gears. No problems as far as I can see.

Then i discovered a problem: When hitting the rear axle with a sledge hammer it moved back and forth on the leaf spring.
There is a tap on the leafspring that goes into a hole on the leafspring-seat of the axle housing. Over the years this hole had gotten worn oval and it allowed the axle to move 4-5mm back and forth. So I welded op the edges of the hole and grinded it perfect size and MOST of the clunk was gone.

Now it only clunks when i suddenly go from deceleration to acceleration in 4th and 5th gear.
So you would think there would be something in the gearbox only concerning the last two gears?
Well I stuck a go pro camera (which has a mic on it) on several places and you can't really hear the clunk when its mounted on the gearbox housing. When mounted on the axle housing however you can hear it.
On the film its seems that the axle is changing angle compared to the body at the exact same time as the clunk appears. But it does not seem to be any slack in the leaf joint bushings or hangers.
I took the driveshaft off at the differential end and checked that universal joint more thorough. There's no slack when twisting the shafts but when i change the angle of the joint I feel a slight "bump" everytime a move past a certain angle. Can this be the noise? The universal joint does not really change angle to much on a car like this but I'm getting hard pressed to think of anything else.

Any ideas out there?

Since it has been a few days, I'll respond, though I haven't had this particular problem.

Great idea using a go-pro with a mic to identify noises, and nice job fixing the rounded out hole!

I've replaced a few u-joints on vehicles other than Sprinters and have seen a fair share of failing bearings. Based on your description, if it were me, I would agree with your conclusion that it was a bearing in that universal joint and would try to find a way to confirm this. Perhaps using a voice recorder on a phone that will record from a Bluetooth headset, and then tape the headset directly to different places on the universal joint or driveshaft. Or find some other portable recording device, remove its microphone and reconnect it with wires so you can tape the mic to different points on the driveshaft and u-joints, driving very slowly, obviously. (I'm assuming from your description that this is happening at low speeds.)

I hear a clunk when going in one direction, stopping, and then applying a good amount of power in the other. Thanks to your description, I will take a look at the leafspring seat of the axle housing!

I have been ignoring it (it is infrequent; it requires a good amount of power applied, like climbing a hill) but had wondered if it might have been a universal joint problem and was following related threads. If I recall correctly, the universal joint design requires replacement of the entire driveshaft, which seemed ridiculous, and apparently there are shops around that will happily modify the driveshaft (or provide a new one) so that it can accept a conventional universal joint. Here's one thread about this; the link for driveshafts.com is old and redirects to a newer page, so calling the company might be a good idea. Also, seems they make Carbon Fiber driveshafts, which would make for an interesting write-up we'd love to read, if you're willing to plunk down the cash for one of those!!!

This thread is the driveshaft thread I was thinking about, with more links and a good photo of a replacement shaft with changeable u-joints not too far in. It's the one I posted in when I started hearing the noise. It never got worse, and it happens infrequently and only under heavy load, so I didn't take further action.

Let us know how you end up finding and fixing the noise.

Sean

Thanx for the input

Hope that the leaf spring seat tip will help you with your sprinter
Like you I wasn't too concerned about it, but it was relieving to eliminate the differential as cause to the noise.

The clunking noise I'm left with now is at high speed only. I can provoke it anytime in 4th or 5th gear at 45mph + but it typically appears at highway cruising speed with a bit of load in or maybe towing a trailer. Then when you put your foot down at the bottom of a hill you hear and feel this clunk.

I found the universal joints on ebay to a fair price, so I went ahead and ordered them. But now that you mention it; it does not appear to be any snap-rings on the stock universal joints. Rather some taps on the driveshaft fork around the bearing caps to keep the joint in place.
Quite unbelievable since the stock joints haven't got a grease nipple either. So you're pretty much supposed to just wait for the whole driveshaft to need replacement.

I believe I will attempt replacing them by acid-cleaning away all the rust, dirt and grease and then grind down these taps with a small bandgrinder. Then I'll tack-weld around the bearing caps of the new universal joint to keep it in place. Maybe put a washer in between to avoid damaging the needlebearings.
If It doesn't work the driveshaft shop will have to fix it anyway, I guess.