alive19

I'm getting a massive clunking noise from the front. It feels like it is coming from the drivers (right hand drive) foot well. The car has done about 230k kms. I have 2 speed transfer case and rear diff locker (off road package).

It happens very repeatably when transitioning from loaded engine to coasting. Will happen at different revs and speeds. Basically as I back off the accelerator it'll start clunking.

When loaded it quiet, no noises going over bumps or full lock turns. My transmission is quiet and smooth at pretty much all gear changes, apart from occasional non smooth 2nd to 1st when slowly slowing.

I drained the front and rear diff and they were clean. Ran a magnet through the oil and didn't pick up much. I've had the front tyres up on stands and backlash in front diff feels ok. I do however get some slop between front and rear driveshaft through the transfer box. Maybe 1/8th 1/10th of a turn.

Rubbers are all generally good on the car. Centre drive shaft bearing looked good from one side.

My only thought is the chain is stretched. Has anyone had a similar issue and solved it? It's a big clunking noise, so it needs to be fixed. Doesn't have that self heal feel.

alive19

Just noticed DAS has clunking listed in the transfer control module section.

Can anyone access TIPS.

I'm interested in: LI27.00-P-045779 Throttle Lift-Off Clunking Noise In Vehicle Speed Range Up To Approx. 50 Mph

alive19

Continuing the monologue...

I've just flashed the lasted firmware for the transmission.

Now I can't reproduce the impending doom sound. Hopefully this has fixed it, but it really sounded bad, so a simple software update seems a little optimistic.

eric_in_sd

Perhaps it is the adaptations. Consider going in (I assume you have DAS or a bidirectional tool) and resetting the adaptations if it recurs.

I got clunky noises at one time that sounded like your description, but they do not seem to have recurred. I thought it might be transfer case, but after looking into it I decided otherwise - chain skipping happens when force is applied, not when put putting around.

I would not be surprised if it were a glitch in the adaptation algorithm. Glad I checked in on your monologue.

eric_in_sd

What is TIPS?

is this in WIS?

alive19

TIPS is where you can access all the TSBs AFAIK.

It is on-line and can be accessed through Xentry. I haven't seen any offline hacked versions.

https://b2bconnect.mercedes-benz.com...ns/xentry-tips

eric_in_sd

A few of the guys here on the forums have bandit version of DAS. Somehow I doubt that will help.

You could try asking these guys but I have a funny feeling nothing will come of it: https://www.tsbsearch.com/Mercedes-B...27-00-P-045779

eric_in_sd

Well, you got me curious.

If you go here https://www.nhtsa.gov/recalls and click the Vehicle tab, entering the year make model you can see TSBs. However, for older vehicles the database is incomplete or something. I found a bunch of TSBs for my GL but not the one you are looking for.

Air2msc

If you haven't solved this, ours was the front prop shaft. It eventually failed and car wouldn't move.

Max Blast

If OP has a 2 xfer case it’s chain wear. I have the same clunking going on under power and I have ran adaptations and it still persists. I have not tried to flash the firmware but I also don’t want to brick my TCM but it’s got 225,000 miles on it. It noticeably creeps forward after being put in park went on an incline so I got a believe that is slack in the transfer case chain, compounded by slack in the parking pawl.

alive19

The software update got rid of the clunking. I'll have to do some adjustments as now the 2->1 gear change is a bit rough.

Yeah likely to still have some chain slack. Just not keen to rush into that as a job.

eric_in_sd

How do you do the software update?

alive19

Xentry / DAS

Depends on whether the module has updates available. My transmission did, so I updated.