I could really use some advice for a friend about a drive train issue
 

A friend who has had his 190e much longer than I have had mine is in a jam. He has some sort of noise coming from the rear when he steps on the gas from a standstill. Once the car is moving it drives fine. I'm guessing that it might be a rear axle issue or a u joint issue. He is frustrated and wants to junk the car. He thought it was the transmission. I told him let me look in to it before you do anything rash. Does anyone have any ideas what could be going on?

What sort of noise? A clunk?

That is a good word for it. A slight grind/hesitation with a clunk when starting from a stop. No noise once the car is moving.

There are numerous rubber bushings throughout the rear suspension and differential area, along with flex discs on the driveline. Any one of those that has deteriorated is a candidate for causing clunks.

Thanks for the reply. What a pain in the neck this could turn out to be.

Best description...is it a clunk or a 'ting'? At low speeds blip the throttle really quick. Does it do it again? If so. Flex disk for sure.

Seems like a clunk and some hesitation than snaps in to place when going from a complete stop to stepping on the gas from what I remember. I will get back to you on that

I agree, my '93 190 made a heck of clunking noise at take off when the right rear sub-frame mount bushing went bad. Then later, the front flex disc went out and also made clunking noises.

But it isnt only a clunk. The car has a hesitation and then like a small grind noise before it locks in to move. Only happens when stepping on the gas from a full stop. Doesnt happen while moving

I cant get under the car yet because we dont have the right kind of jack. I did take some pictures though. I cant tell if the disc is bad from the pictures. I will post what I have so far. He also did tell me he sometimes would hear a small thud when making slow right turns. I saw some oil/grease on the axle but its not wet. He has a oil leak up front so I think that may just be accumulated oil/dirt that blew back over the years while driving. His front disc was changed 50 or 60k miles ago. I dont know if his rear disc was ever changed. It may have been. I think he is around 165k now

Could it be the shaft, the axle or some sort of bearing?

Some more pics

Maybe the key isnt the clunk? Maybe the key is the hesitation and sort of grind noise that comes before the car moves.

Be sure to also check the front flex disc. Does the transmission go into drive smoothly with no hesitation? When was the trans. fluid and filter last changed?
Has the differential fluid been checked or changed?

Can I check the front disc visually without the car being on a lift?

It seems to stick or grind a bit when starting in first gear from a stop. I noticed the rpms go up till it seems to snap in to place. The clunk sound seems to come from the rear though. Maybe they are not directly related? I couldnt tell if there was anything wrong with the rear disk visually by sliding under the car. Isnt there some sort of drive shaft bearing? Could that be the cause?

The front disk was changed aroound 50k miles ago. The tranny fluid and filter around 40k miles ago.

If the car seems to drive ok when not starting off in 1st gear from a complete stop would it be crazy to drive it 10-15 miles to a mechanic?

I was able to slide under the car a little bit and take some pictures of the front disk. Does anything look out of order with the front disk? Should those bolts be seated that way?

From what I know those mounting bolts have all shifted quite abit.
Wear, misalignment or just plain bad all could cause that.

Thanks bob I was hoping the front disc would not be the problem but if I can be sure that is the problem I would feel better knowing for sure.

Do you think that front disc could be causing the symptoms that I mentioned? Did you see any problem with the pictures I posted of the rear disc area?

Definitely needs attention as there are gaps which allows for slack upon movement (hence why you only notice it while moving).

Not entirely sure that is the whole problem, but it sure would be contributing. Common wear item every 60-80k, so just change it out for both good measure and preventative maintenance. Don't want that baby to crack in two while you are on the freeway!

The clunk in the rear of the car is probably the differential mounts. I have that in my 87 300e.

There would have to be a hell of a lot of slop in a flex disc or an axle to cause a noticeable hesitation. Even 5-10 degrees of slop, which would be rather a lot for a flex disc or axle would barely be noticeable as a hesitation, but it would certainly be likely to clunk.

I think you have more than one issue here. Sounds to me like the transmission is engaging late, and when it does the sudden torque increase causes the slop in the flex discs and/or rear axle(s) to clunk audibly.

That rear differential looks pretty oily, you may want to check that the fluid level is adequate too.

Check the trans fluid level. Low fluid can cause all sorts of weird trans symptoms including slipping, late shifts, etc...... A clogged trans filter could also be to blame.

Thanks for all the replies. I checked his tranny fluid level. That seems fine.

I dont know how to check the differential level. Can anyone explain that for me?

Mechanic wants $400 to do the front disc if that is the problem

It is noticeable when stepping on the gas from a stop. Once the car gets moving it is not noticeable.

Is it a hard DIY procedure for us to do at home in the garage?

Not too terribly hard if you have proper equipment.


CAUTION - When you disconnect the drive shaft, there is no longer a park pawl holding the car in place. The car must be on a level surface and carefully chocked!


How much of a hesitation are we talking about here, anyway?

I'm still not convinced the problem is not in the trans. You say the problem happens every time you start from a dead stop. Well, let's use our imaginations for a second..... Any slop in the drive train will get taken up when you shift from park or neutral into drive, right? The torque from the trans is supposed to always be present on the drive train when the car is in gear. This is why the car starts to move by itself when you take your foot off the brake. So, that slop goes away the very first time you go into gear, right? Okay, so how then does it re-appear at every stoplight unless the driver is shifting to neutral?

The only way this could be happening is if the trans is not applying torque to the drive train at all times, and that points to trans problems.

It's easy to replace. When I replaced my front flex disc, I had to remove the rear one so I could slide the drive shaft back to remove and install the front one.

Not a tremendous amount. I did not notice it at first.

I also have not noticed it in reverse yet.

Is it basically removing 6 bolts from the rear and removing 6 bolts from the front and just pulling it out? Are there any other parts like the bearing I should check out while it is of?

Yes, that's about it. One thing I like to do is put witness marks on the shaft/connectors so that the drive shaft goes back on the the same position.

Remove filler plug at differential, stick your finger in the hole, if low, add fluid, screw filler plug back in.

I read about that and I would do that. I think I could do this job if I had a lift for sure but I'm concerned about trying to do it with little clearance on jackstands or light. I'm also concerned because I'm not sure of the problem yet

Sounds complicated. :)

In all seriousness is it just if the fluid is below the whole it is low? I havent used my finger as a dipstick before. :)


Last dumb question. Which side is the filler plug facing?

Before doing anything else, have your friend take off in the car and watch the rear wheels real close. I had my wife take off in hers and I could see a lot of movement in the right rear wheel when the sub-frame mount went bad. It made a hell of clunking noise when taking off, then smoothed out.

That is really interesting because that is how his is.

From a stop you have hesitation, slight grind, clunk then smooth going

I dont even know where the sub frame mount is. I will look that up.

It's on the passenger side of the differential. I just changed the fluid recently on the 190 and the SLK230.

Maybe after this you will want to change your user name to "Dipstick":D

Well, you need to isolate the problem. Does the above start happening before the rear wheels start turning?

After I saw my wife's 190 right rear wheel moving around at take off, I jacked up the right rear, removed the wheel, then used a 2 x 4 to lift up on the suspension. I could see movement/play in the sub-frame mount. It was obvious that the rubber bushing was toast.
It was hard to replace but I got it done in one afternoon.

Thanks. Only my friends call me that. :)

I think all that does happen before the wheels start moving. I will double check that and get back to you.

If it is a tranny problem I think he would have to sell the car because he couldnt afford to put a new tranny in it.

OK guys please bear with me because we seriously need and appreciate your help with this situation. We think we are getting closer to narrowing the symptoms and the problem down. Here are some updates:

1. We tried shifting directly in to 2nd and 3rd gear instead of drive to see if that made a difference. Trying to figure if it was a 1st gear problem since it drives fine once moving. It didnt make any difference.

2. I did notice it not only when starting off but now when hitting the brakes and coming to a stop we feel it also. It seems to be coming from the shaft or axle area more than from the tranny but that is just my hunch for now.

3. When we step on the gas hard we feel it but if we step on the gas really lightly to start off it doesnt happen at all.

4. I dont ever feel it in reverse but since I'm usually going very slow in reverse.

5. Do these descriptions of the problem help anyone in trying to figure it out?

6. Does those bolts look like they are lined up correctly on the front disc pictures or are those curved areas supposed to be in the raised curve area of the plastic/rubber? I posted the picture previously in this thread

I have a few updates but before I get to them I really wanted to thank everyone in this thread for their help.

1. My buddy was so frustrated and worried about all the things this issue possibly could be that he just wanted out of the car so I bought it from him this weekend. I now own 2 190e's

2. I finally got under the car with the correct jack, jacks tands and a light. Visually both flex discs looked fine. I was stumped and concerned what could be the problem. I started playing with the drive shaft and noticed some slack but not a large amount. When I went to the rear of the car I didnt notice any slack but I did notice slack from the front. So I went back to the front disc. While visually it looked OK I noticed when I turned the drive shaft 2 of the (15mm socket) flex disc bolts were moving. I hoped I could just tighten them and the problem would go away but the problem remained although it seemed lessened. The bolts still seemed to move even when very tight so my guess is that the flex disc is bad. I'm going to hope that is the only thing causing this problem. It was changed around 61,000 miles ago.

3. When in the back looking at the differential there are 2 round wheels on each side. I dont know what they are called. 1 side seemed totally straight. The other side did not seem as straight. Do you know what the wheels are called? Would 1 not being 100% straight be a major issue?

4. Would I be better off ordering a Lemforder or a Febi Bilstein front disc?

Thanks once again. I guess I will order the front flex disc, attempt to change it out myself and hope that was the problem. It probably is. Would seem a bit coincidental for that not to be an issue since it is 2 of the 3 bolts that are moving.

;)

The first part of the flex disk's wear comes at the holes as they widen and can cause the clunking you are noticing. The washers actually mask the holes to some extent, but under a closer inspection (and turning like you did), you'll notice quite some slack.

Now get on and swap'er out!

I would go with whatever is cheaper. Both are quality, but these flex disks wear either way. Unless someone has used both and can comment of course! (which would be at least 150k+ miles worth of experience on the same car under roughly the same driving conditions)

flex disc
 

flex disc not mounted correct, should be aligned in proper recess.

ps2cho,
Thanks for the explanation. That makes me feel more confident that the disc is the problem. I ordered a new Bilstein disc 15 minutes ago.

Pop & Blow Thanks for the tip. Sounds like that could indeed be the problem.

OK the good news is I got the part.

Bad news is the tranny cross-member bolts seem to have been put on by the incredible hulk. I'm having big trouble getting them off. I dont have an impact wrench. I used to use a long torque wrench for leverage in the past and that worked well but that wrench got up and walked away one day. Any advice on how to get the tight bolts loose? Should I go buy another torque wrench or some sort of breaker bar?

Crap crap crap.

One of the tranny cross member bolts just snapped off like butter when I used the breaker bar. I'm afraid somebody went crazy with an impact wrench and the other 3 might snap off as well. I just hit the outside of the bolts with liquid wrench (I should have used that in the beginning) but I dont know if it will help at all. I'm desperate for some help here!!!

OK I got the tranny crossmemeber bolts off but when I did I wasnt even sure if I was going about this the right way so I put them back and figured I will try a different way tomorrow. I think I'm going to try to remove the rear disc and then the front. Maybe after I remove the rear I can slide the drive shaft backwards a couple of inches to allow me to change out the front disc.

The disc bolts on are so tight and even when they come a little loose they are a pain to keep undoing. Is that normal? Also when you went to loosen your bolts did you use a box wrench in back on the nuts?

Maybe it's just me, but wouldn't it remove a certain amount of guesswork and suspense if you just used the FSM?

The online manual I have isnt very specific for this job/car but if you know of something that is I would really appreciate the heads up. Thanks in advance.

Slowly I'm making some progress. I got all 6 rear flex disc bolts off. Looks to be a Mercedes replacement part. I doubt it is original because it is in really good condition. Even with all 6 bolts out it seems stuck in there. Any hints on how to get it out after the bolts are removed?