C124 Driveline clunk - not flex disks or diff mounts

[EVL124]

Hi All

Have an annoying clunk in the 320CE, and am at a bit of a loss as to what it could be.

I have replaced both flex disks, the diff mounts front bushings in rear subframe, trans mount and both motor mounts.

Basically upshifting, even under full throttle/redline is fine, no jerkiness or anything. Its the downshifting which is a problem, if I manually select 4th or 3rd etc with the shifter its OK, but if I do a kickdown from 5th to 3rd a lot of the time I get a very jerky downshift and an audible clunk/thud. I can also hear it in stop/go traffic when I coming to a stop and the trans is downshifting. It doesn't really appear to do it too much if I cruise in gear and throttle on and off (but can get it to do it slightly) which leads me to believe it could be trans?

Another thing, from memory it doesn't seem to do it from 5th to 4th (electronic) so would that point to vacuum modulator perhaps?

Any ideas? Its driving me insane!

 

[WDB124066]

Did the new parts make any difference at all?

Can you tell if the clunk is from the front or toward the rear??

 

[EVL124]

Flex disks cured the vibration at 100km, and diff mounts cured a different clunk but nothing seems to have affected this one. It does sound like its coming from the rear, but that could just be the sound traveling down the trans tunnel...

 

[WDB124066]

Yes it could well be.

Do you think you may learn something from removing the rear seat and have someone drive it for you while you listen for probable location.

It is just possible that somewhere in the rear suspension mounts / links there is a small problem. Have you checked the CV joints - guess it would do it all the time though.....

Despite this, with all the work you have been doing the car must be starting to feel quite sorted now.....?? I have been busy in PNG but is it time for me to travel the road north now for a goosy!

FWIW MB in Germany will rebuild your box with equipment & experience that is just not available in NZL. Very tempted to send mine back to the Fatherland - do you think we need to start pricing large crates!

Edit: Did Harry offer any thoughts???

 

[EVL124]

He hasn't looked at it too closely, but when I drop it off for harness replacement I think I will just ask him to keep going till its diagnosed, he did mention it *could* be the U joint which would mean a replacement driveshaft...

Yeah, car is feeling pretty good now, still nowhere near my **** retentive standards though - I keep noticing things that I need to do!!

I would have spent at least half of what I have paid for it in maintenance etc by now I think - for a laugh check out my list: http://www.eurosport.org.nz/forum/viewtopic.php?f=154&t=8600&p=126189#p126189

Yeah, let me know when you are coming up to AK next and will sort out a catch up.

 

[WDB124066]

Got one to try, good way to see. There was a nice red coupe on trademe the other day that looked like it could contribute to the seating problem I have. Could be a cracking parts car if you are that way inclined.

It's a nice car, and deserves a refurbish. Don't give up.

On the parts front I forgot to mention before, go see Brad at Coutts - he runs the parts department for the North Island, tell him I sent you and he will give you Genuine MB parts at a price that will make your eyes water - for all the right reasons. Call him first though, he gets very busy.

 

[EVL124]

Could be worth a try!

I saw that too, the other half would kill me if I brought another one home though!

Main thing I would want from it would be entire interior to replace my crummy cloth which would be at odds with fixing your seating problem

Another one popped up today as well with a starting bid of 5k.

Definitely not going to give up, it will be immaculate once I am finished with it, just has two incredibly annoying problems - the clunk and rough idle!!

 

[WDB124066]

Who said anything about getting it home!

Mmmm, got a rebuilt tansmission too. I really only need the entire seat frame without the cover. I am sure we could work something out. Drop me a line before you get serious.

Does it ever get to 95 - 100 in the summer around town, I had a slightly lumpy idle; was running lean.

 

[EVL124]

I definitely wont be getting it, but if you end up buying it let me know

Yep, on the move it hovers on/just above 80 (I have a 79 deg t-stat) but in town on a hot day it does creep up to 95-100, idle is rubbish at all but cold start though, so definitely a harness (hopefully) ETA/ECU issue (hopefully not)

Out of interest how many kms do you get out of a tank in town driving?

 

[WDB124066]

Not too sure to be honest I live in the country. Normally get an easy 600 out of a tank - if I take it easy.

If the fan is working correctly, I wouldn't mind betting you are running lean old chap. Idles sooooooooooo much better when mixture is set correctly. Just a thought.......

 

[grober]

Propshaft central bearing flexible mount or the bearing itself. The bearing is rubber mounted in a flexible saddle attached to the bottom of the floor pan. Any weakness will reveal itself during episodes where the propshaft is expected to transfer large torque loadings/ reverses.

 

[EVL124]

Harry confirmed its gearbox, damnit! - Forget what the exact issue was.

Also, the "new" loom that was sent over had a 1994 manufacture date, and had been sitting in the humidity of Singapore for all of those years - I'm sure you can see the issue there!! Needless to say, they are sending another one over ASAP.

Once that arrives will get that replaced, and 'box ripped into at same time.

 

[BlackC55]

Check the rear subframe bushes too.,

 

[ss201]

I have a W201 2.6 auto. Bought 4 years ago with 130k miles & FMBSH. When I first got it, it had a clunk on the drivetrain: not bad, but noticeable. Took it to a recommended, long-established M-B indie for a service. Also took new front & rear prop shaft couplings (donuts) with a request to change them if that would solve the problem. He said the existing donuts were in good shape and didn't need changing, but the problem was "a bit of wear at the gearbox end and the same at the diff. Leave it alone, sir, they all do it and it'll go on for years like that". 4 years & 70k miles later, it still clunked and nothing had broken. However, in the last 2k miles I've had all of the following replaced:

febi rear subframe mounts (front), both donuts (Lemforder), propshaft centre bearing (febi), all new febi control arms (4 per side), rear shocks & springs (Bilstein) front shocks (Sachs) front suspension top mounts, engine mounts, gearbox mount (all genuine M-B), new rear ARB drop links, mounting brackets & bushes........ and.....

.....the drivetrain still clunks! Not as bad as it did, but it's still there. So I reckon the indie was right, four years ago: bit of wear on the end of the gearbox and a bit on the end of the diff. Now that's the kind of techie speak I appreciate and understand!

Incidentally, if you're interested, the indie was T. W. Neale of Himley, near Dudley in the W. Midlands. Nice folk and almost speak my language.

 

[BlackC55]

Check the rear subframe bushes too.,

Ignore me. I should have read the first post properly