1998 ML320 - Drivetrain "Clicking" - PeachParts Mercedes-Benz Forum

bbrewer · #1 10-29-2002, 10:04 AM

Hi Gilly;
Hopefully, this is the last problem (but may be the worst of the bunch).
Regardless, I just got this vehicle, and it currently has 118k miles on it.
It runs fine (other than the ESP/BAS dash light on), but I've noticed that when I accelerate really hard, that I get a series of "clicking/clunking" noises out of the drivetrain.
It does it for several seconds, and stops when I let up on the accelerator. It makes no abnormal sounds in everyday driving.
It doesn't feel like u-joints or something like that is "loose", just sounds like I'm about to break something if I don't let off on the accelerator.... :-(
Any clues??
Could this be related to the ESP system not working correctly??

Thanks!!

Gilly · #2 10-30-2002, 09:34 PM

Barry
Sorry to respond so late, I've been back to good 'ol Chicago for 211 training (new e class)
Haven't had alot of complaints like this, and to tell the truth I'm lousy at diagnosing a "noise" complaint without personally hearing it.
A few ideas would be that I've seen the front exhaust bracket crack on these, that can give a noise on acceleration like you describe, and also we've had a few catalytic converters making noise, the matrix inside the converter can crack and vibrate at times. It's not covered under the 80,000 emission warranty as it doesn't cause a check engine light or affect emission performance, just annoying.

Gilly

bbrewer · #3 10-30-2002, 09:52 PM

Thanks Gilly;
I'll get under there this weekend and take a peek under this bad boy.
I'll let you know if I see anything amiss.

Barry

bbrewer · #4 11-09-2002, 06:48 PM

Finally got the time to get under there......
Only thing I noticed amiss was a missing bolt that mounts an exhaust pipe bracket to the bottom of the transmission.
Replaced that, but no change.
I'm wondering if it isn't related to the full-time 4-wheel drive.
It sounds/feels almost like a friction clutch releasing and then grabbing, and it only occurs from a HARD acceleration from a dead stop. And it only skips 2-4 times and then is done......
It seems like a bad thing, but nothing ever bad happens, it just "sounds" like the drivetrain is about to break.... :-(

Thanks.

Q · #5 11-09-2002, 09:28 PM

Isn't that what a CV joint will do??

bbrewer · #6 11-09-2002, 10:51 PM

Could be, but it doesn't feel or sound any different while turning. IT only "slips" under HARD acceleration, and the wheels are usually straight while I'm doing it.
Thanks,

bbrewer · #7 11-19-2002, 12:57 PM

Is there a chain or belt that could be slipping on it's toothed-sprocket in the transfer case??
The CV joints checked out solid with no play, but yet there IS this slipping/ratcheting noise upon very hard acceleration.....

Thanks!!

Gilly · #8 11-19-2002, 07:58 PM

If that were happening, I would think it would be making alot more racket than it is now. Have you tried rapping on the catalytic converters yet with a rubber mallet?

Gilly

bbrewer · #9 11-20-2002, 08:34 AM

Oh yes, I pounded around down there while I was down replacing that transmission bracket bolt.....
Everything seemed solid and tight. No rattles from the exhaust system.
And it IS a pretty loud racket, but it just lasts about 2-4 seconds, depending on how hard you are stomping on the accelerator, and it only occurs from an initial dead stop.
Somewhere in the drive train there must be SOME kind of sprocket that is slipping, because it's JUST like a clutch slipping in a manual transmission when you rev the engine but the rest of the car hasn't "caught-up" yet.... :-), only it makes a "ratcheting" noise, like "teeth" on a gear slipping.
The rest of the time driving you wouldn't even know anything is wrong....

Thanks.

Lebenz · #10 11-20-2002, 11:33 AM

Long time ago, I remember someone with a similar problem on a ML that was caused by a loose heat shield. Just a thought....

bbrewer · #11 11-20-2002, 11:52 AM

Sadly, I just heard from a repair shop.
They say it IS the transfer case, and that there IS in fact a chain/sprocket combination inside that is "skipping".
He also went on to say that Mercedes has come out with an upgraded transfer case, and does not recommend rebuilding the "older" style.....
This is a 1998 ML320 with 119k miles on it.
Questions:
Is this true about the upgraded transfer units??
The shop quoted me 5 hours labor. How hard is this for a reasonably competent home mechanic?? I've replaced clutches and transmissions before, but never worked on a 4WD.
Any special tools or tricks to know??
Or is it a pretty straight-forward R&R, with just a good day's effort??
Thanks.....

Lewis · #12 11-20-2002, 12:59 PM

Barry, I think they're way overestimating. Mine was replaced under warranty at 45K miles due to binding on turns. The part was about $1000 and service was about $200-300. I'm sure it's cheaper just to replace vice rebuild. I was surprised the thing wasn't 2 or 3 times that much, but if you look at it, it's really small compared to an American 4X4 and the thing is completely separate from the tranny. Looks like it would be a farily simple job, but Gilly could say for sure. The costs aren't on my bill because it was warranty work, but I'll check on the hours for you. When I checked my shop's part counter a few days ago on fuel pump part numbers, he showed me his screen and how it listed the whole sequence of old and new part numbers. You should do the same to see how may updates there are for peace of mind. 98 and 99s had lots of transfer case complaints and problems like mine, so I'm sure there were updates.

Lewis · #13 11-21-2002, 12:49 PM

Barry, checked my invoice last night. Looks like they billed 3.2hrs to remove and replace the transfer case and .4hrs to swap some parts from the old unit to the new one for 3.6hrs total. Maybe my shop is little more skilled than yours. I'll bet Gilly could do it in 2 flat though.:p

bbrewer · #14 11-21-2002, 02:57 PM

Thanks.
I ordered the replacement yesterday, and I plan to take the old one out tonight. We'll see how it goes....
My shop quoted me about $500 for labor......
I don't mind spending 3.6 hours, or even TWICE that, doing it for that kind of money.....

But I AM hoping Gilly might pop on here to let me know if there are any tricks or anything that might save me some time or grief.... :-(

Thanks again.

bbrewer · #15 12-02-2002, 01:56 PM

Okay, THAT's done....... :-)
Just a brief rundown, it's really NOT difficult to replace the transfer case, and it's about 1-1/2 to 2 hours each for removal and then replacing it.
I did waste about an extra hour trying to install the new one by myself. Bolting and unbolting is pretty much a one man job, but getting the new one from the garage floor to it's rightful place snugged-up to the back of the tranny IS a TWO-MAN job......
Just too much weight at the same time trying to line things up.
Trust me, phone a friend for this step.....

Anyway, runs like a champ now......

Thanks to all for their advice and encouragement.

Barry