bmwpowere36m3

If its an earlier 7G then it sounds like it could be the TC lockup... higher gear, light throttle, vibration felt through vehicle. More throttle and it improves. First suggestion would be fluid/filter change and inspect for debris in pan. Additionally re-adaptation of transmission may help, assuming the TC lock-up clutch is too far gone or box contaminated.

Left Coast Geek

I hopefully fixed that for you.

Lowacura

Thanks for the replies!....

@Left Coast Geek - I only took it to AAMCO to see if they can figure it out or suggest changing the fluid then I would have just done it myself at home- Free Diagnostic lol.... Car is originally from California, my dad drove it up here and said the car was mine which is the first time someone ever gifted me a car, pretty cool. But with a catch.... Those import folks said it would be around 5-7 grand to fix the transmission if that was the issue, and if that's the case, no thanks...

@bmwpowere36m3- AAMCO said something about the possibility of the Torque converter not locking up right on 6th, or said it was locking up, I don't remember what exactly. All I soaked in was $3750. I tried the Re-adaptation method or the relearning of the transmission and it did nothing...

My question is... instead of spending over $140 or more on Genuine Mercedes Transmission fluid, can I use any other cheap transmission fluid that's "mercedes approved" just to see if tit fixes the issue? If so, any recommendations? If it fixes the issue, ill drain it all out and spend 600 dollars to have a shop do it if I have to if it worked. I fear that it might be some gearing issue, but with all the reading i have done, alot of issues were solved just by changing the fluid. I am still hopeful.

nc211

honestly the brakes have felt completely different since a 40k visit to a dealership for a b service where they replaced the fluid. After that visit, the have felt hard. I wonder.....

it’s day 2 at a new dealership and still nothing to report. They started on the diagnosis today. I bought our GLS from this dealership, and they know I’ve not had good experiences with Mercedes dealerships. So it told them to not rush the job. I don’t need the car for several days, just take the time needed to pinpoint the problem. Around here, there are so many MB’s roaming the streets, I don’t think some of these dealerships get the proper amount of time to figure anything out and just rush it. Hopefully I’m avoiding that here. In my eyes, I have two, and if they want to make money from me to service them, then this would we that chance to prove to me they’re not just tossing out the corporate verbiage. I have my fingers crossed!

I think it’s either the brakes dragging or a bad bearing somewhere in the driveline from the front to right about where that center bearing is located in the prop shaft. Maybe a bearing inside the transfer case, who knows. I do know when they changed my trans fluid about 8k miles ago (around 48k miles), it was still red and had no metal shavings, the magnet was perfect. So I’m not leaning in that direction of it being a transmission. Maybe the front diff, but at only 55k miles, just doesn’t compute to me. Especially when not really driven in snow where the rear wheels would spin and not the front. Time will tell I guess... can’t wait to see this bill....

I did have to laugh yesterday when I received a random email from the dealership advertising pricing on new and CPO’d cars on their lot. Figured they were priming the pump just in case. Ain’t happening! I’ll park it on blocks in my garage and tear the damn thing apart myself.

Left Coast Geek

I think your car specs Mercedes 236.14, which includes Shell ATF 134

you can /probably/ get away with quality brand name generic Dex/Merc red ATF as I think its pretty close to the right spec.

bmwpowere36m3

I wouldn't be concerned over using generic DexIII or like a Valvoline Maxlife and damaging the transmission for this "experiment".... HOWEVER, my concern would be that the fluid characteristics could be different enough and not give you conclusive evidence on whether its "solved" the issue.

Another consideration before proceeding too far forward is simply dropping the pan and taking an oil sample and sending it out. Then you can check for debris in the pan and get an analysis of the fluid for wear material, coolant contamination, etc...

I'd take a $100-150 gamble, before tossing the car or replacing the transmission/TC.

Lowacura

I found a reputable import specialist that does a complete diagnostic check for $60. They said they will look over the car and tell me whats wrong with it. I took it to a transmission shop today and they told me the engine mounts and transmission mount was bad and that it was speed related. I countered back and told them i can be going 40-60mph no issues on 5th gear but as soon as I hit 6th it shakes. He was stumped and still insisted the engine mounts were the place to start. So he recommended an import specialist. (makes sense) but everyone has their own opinion and cant pin point the issue. Except i did. and they don't take my word for it.

How do I know my car specs for sure? In manual mode it goes from gears 1-6 and then D. Does that mean its a 6 speed not a 7? I cant even find the dipstick for the trans fluid on this thing? Do i have to pump it in from the bottom on this car?


THANK YOU ALL FOR YOUR HELP!!!

Lowacura

Oh yea, there was this antishudder stuff i saw online in a red tube. Should i try that? Its only 10 bucks... or should i steer away from it?

bmwpowere36m3

Motor mounts generally can be felt at idle, when putting the car into R or D while holding the brake pedal. Sometimes when the car is cold, its more apparent and it usually clears up as you drive or is less noticeable. You feel vibrations in the floorboards and even in the steering wheel.

You can also check for signs of leakage from the mounts and/or if their compressed (which is hard, with no basis for reference). With a proper scan tool, an indy, dealer, or transmission specialist could further diagnose the potential for TC lock-up issue.

Lowacura

OKAY. So I made some more calls to indy specialists. I got filled in for tomorrow at 10am. He said he has all the special tools required for that car and mentioned alot of possibilities it could be, like selonoid, connection issues with the seals to electronics, valvebody etc. Issuues mentioned in the forums... He also mentioned he has a tool or computer that connects to the car and can monitor each gear while driving realtime, which the other shops did not do. So I am dropping it off tomorrow and hopefully have some real answers. I will keep you all posted. Just hope he can actually give me a diagnosis.

nc211

On mine, after 3 days, I got the “we cannot replicate the problem” call today from the dealership. 3 other indi mechanics could hear and feel it without a doubt. I swear, I could pull into the servicing bay of a Mercedes dealer with the damn thing on fire and they’d say “fire? what fire, we don’t see no fire....”

im going to toss some wheel bearings, flex couplings and a new center bearing at the car next week, along with new front end blanks on the rotors.

Edit - rotors ordered (Zimm blanks) and ceramic pads Akebono (spelling wrong but whatever) today for Tuesday delivery.

Before they go on, I have an appointment Monday morning at an actual wheel repair shop to make sure the rims are 100% round. Guys did say they were slightly bent, capable of being balanced out, but as sensitive as these cars are, I think it needs to be 100% round and NOT doing the dealership way anymore. My understanding is some guy comes once a week to the dealerships, pounds them back in round to the point of being able to balance them, and collects his fee. This time, they're going on a press that will heat them up and press them to perfectly round. If that happens to make a difference, then I know it's the wheels indeed. The front rotors and pads are getting replaced regardless. Clearly enough material from the pads have baked onto the rotor again as the car is skipping badly at 70mph with moderate braking effort. No more MB OE rotors/pads on the front here. Lesson learned.

nc211

I really would like to figure this out for folks, because I just struggle with the idea of it being some major part. Not trying to say my car is any better or worse than the others, but as kind and gentle and willing to spend a few thousand on her, has this problem too, then it has to be something in the wear and tear area that we’re either overthinking or overlooking. It’s like the seat issue a few years back. A simple fix for those with the issue with an added spring and some properly placed shop towels under the seat pad.

looking over the dealer notes from yesterday, they comment of rust on the inside of the front rotor and that is the cause of the brake groaning noises. Not flash rust, but actual rust itself. Strange as the car isn’t a beach car, garage queen, always washed every 10 days or so, etc. the rotors are genuine MB from 2018 with now 25k on them. So, I am hopeful this is a contributing factor. The droning noise sounds like a weaker version of the brake groaning noise actually when using the brakes. I’m hopeful....

S-Prihadi

nc211,
Is there a dyno machine in your area or within reasonable distance, which is a 4 wheel drive type and wheel hub version. Not the roller ones.
This kind of machine can produce drag resistance equal to a car moving on the road under variable load condition like gradient and so on.
This is one of the brand I have seen in my country and it also is sold in the USA
http://www.dynapackusa.com/product.htm

The problem with testing a fault condition which needs the car to move at a certain speed, experience certain load and yada yada is ... it is not easy to replicate on real road short of having a real test track.
I think this wheel hub 4 wheel drive dyno can assist you as the amount of wind noise can be reduced to NIL and you can focus on your noise based problem much easier.

nc211

I got under the car myself this morning while having a wheel fixed. Dollar for donuts I’ve found the problem. Take a look at these photos of my drivers side front brake rotor on the inside. There is about an inch ring all the way around it that is extremely rough. As the pads glide on the surface, they’re probably harmonizing on that rough surface.

so, it’s the brakes after all. No more MB parts for front brakes. Will know for sure tomorrow when the new ones go on, but I’m willing to bet a steak dinner this is the cause of the droning noise for me. Nobody who has looked at the car seems to realize these brakes don’t have spreader clips...

bmwpowere36m3

That'll definitely make noise and shudder when braking... as far a droning while driving, hopefully it resolves. Even without spreader springs, the piston seal always retracts the piston a minute amount after releasing the brakes. Granted that might not be happening if the pad/caliper/guide is not "free" to move.

I would have suspected or inspected that solely based on the braking noise. Whereas droning in cabin... less so, but it could depend on how loud and/or sensitive one's ear is.

nc211

I’m willing to bet a tiny little pebble is sitting between the rotor and the pad and is embedded into the pad to the point it can’t break loose. You can see the little groove between the raised areas. I suspect it’s just buzzing away on that pad, to the piston and throughout the lower control arm and outward.

Why my shop nor the dealership didn’t catch this, or even suspect it, is a whole different story. But I’m willing to bet that once the new rotors and ceramic pads go on, the problem is solved. Also explains why it goes away a bit when it’s wet out (lubricant) and the sounds changes ever so slightly when the angle of the road shifts left to right, shifting the weight of the car.

Bad bearing, bad diff, bad transmission... whatever’s. Only bad thing here is I got lazy and didn’t take a look myself, otherwise I’d of spotted this long ago. Also explains why I get brake dust on that wheel worse than the other. Front look fine. But the back is basically destroyed.

I think the moral of the story here - have a droning noise - check the inside of your brake rotors before anything else.

one wheel was bent, now fixed and even smoother than before (which was glass).

im also reminded that having a MB also makes you a target for the upsell. Guy this morning said I needed two new wheel bearings, and the transfer case needed new fluid. When I explained to him how he would change the transfer case fluid, he said it’s easy as the case is right in the middle of the car. BS.... transfer case is inside the transmission and lubricated by the transmission fluid. I think once he realized I knew more than he thought about the car, he backed off. I just told home to fix the wheel.

nc211

Ok closing in on it. The new rotor and pads have made a nice difference and they’re now completely silent. Now we can hear it more clearly. We’re pulling the wheel bearing Thursday. The sound is exactly what you’d expect from a wheel bearing that is starting to fail, even though the wheel is tight. There is no mistaking the noise though. Humming at 60+, rotating tires doesn’t matter, tossing into neutral doesn’t matter, and definitely localized to that front drivers side wheel. Couldn’t get a locational pinpoint with the bum rotors and pad drag before. Now we can.

nc211

Go fund me page being set up around the corner from the blood bank to now cover costs. At this point in time, I’m technically dead due to blood loss and this is my vampire self talking...

ok... the front diff is leaking at the pinion seal. No telling how low the gear oil is, but thankfully caught before burning up the diff. So...out come the axle to drain and repair the seal.

Between the new rotors, fixed bent wheel, new front bearings, fixed differential... looking like a $3k repair bill... of all of that, while the rotors were bad in general, I am thinking the droning noise is indeed the front differential getting low on gear oil.

Because of the design of the front diff on these cars (no drain/fill plugs), the passenger side axle has to come out. Cost is about $1k.

good thing i love this car and plan to keep it for many more years... At 7 years old now, cost to maintain/repair is averaging out to about $1,000 per year. I’d say right on cue for a Mercedes Benz....

S-Prihadi

Damn, really none of those oil ports ?

nc211

nope. The passenger side axle comes out and then you pull the old fluid out and new fluid in, then reassemble. Why they did that, is beyond me. Just stupid. I think the idea behind the design is that they probably thought lifelong fluid since the rear takes the abuse with a fixed 55/45 power split between rear/front. But....

in my situation, the diff is probably fine if the pinion seal wasn’t leaking now. So for me it’s a repair regardless.. would not surprise me if due to lack of driving much over the past year and the seal dried out.

But I will say, this is about as far as I go with this repair. The sound is coming from the front of the car. I will have essentially replaced or serviced nearly every moving part up there now. Bearings, wheels, rotors, and now differential. If this doesn't do the trick, then I haven't a clue and calling it a day. Only other thing I could think of would be an axle bearing, but not sure if the car even as one into the differential or not.

bmwpowere36m3

I know earlier W212 front diffs had a DRAIN (don't recall later MY)... no fill, which "needed" to be thru the passenger side axle (once pulled out). Some ingenuous members figured you could fill thru the drain, like then doing the transmission. Both my W212s have some leakage from the front diff. Pulling the intermediate axle (which risks damaging the seal in the transfer case) and all the work associated with it... yea, I'll drain, refill and live with a little leakage.

The diffs and transfer-cases, notorious for leaks. On one, we replaced the intermediate seal twice because it kept leaking... master tech friend asks, "how many times did you replace the seal, twice... need to do it at least three times....hahaha"

bmwpowere36m3

Oil leakage, the amount, can be deceiving...

I know you've done a lot of work... and it sucks when it isn't working. Maybe take step back, because honestly you might replace the seal and oil and still have a drone. Almost a come to Jesus, moment.

nc211

Yep, I am approaching that moment now. If the noise is not in the front axle/wheel/diff, then that's when I call it. Not messing with the transmission here. I'll just look to replace it later on for something else. All of the symptoms here speak to something in the front. I can't think of anything else it could be. It's not the motor given the ability to kick it into neutral at 80mph and no change in feel. It's not the transmission either given the same scenario as neutral disengages the gear box. Rotating tires doesn't change it either. It's something that spins and/or meshes together. All things seem to point to either wheel bearing, differential, dragging brakes. One if fixed (brakes). We'll see about the other two.

I've spent this much because the car is paid for, only has 55k miles, and I only drive it about 5k - 7k miles a year normally. So lots of life left in her, and given the new parts now, even more so. That's the hard part about it. The car mechanically is as pristine as I can get it, except for one annoying thing that we can't seem to figure out. If this repair from front rotor across to the other front rotor doesn't fix it, then I'm stumped for sure.

All I know is tomorrow night I have to pick it up and take it for a 3,000 mile road trip to SW FL from DC, back up through Alabama then back home. I'd prefer to not listen to the noise if I could avoid it.....

Arrie

Indeed you have done a lot for your car and have given us all lots of good info about it. Thanks for that!!!

But, two items I don't see worked on are the center bearing and the drive shaft U-Joint. With drive shaft I mean the shaft from gear box to rear differential where I understand the center bearing is located right next to the U-Joint. I have not looked at in my cars but saw some MB parts catalog with this kind of pictures...

Anyway, a humming sound in car that does not change with speed typically is some natural frequency exited by a rotating weight. I read in an earlier post that it appears at 50-80 mph and at 85 mph it is silky smooth.

Natural frequency is a "funny" thing that appears even when the exciting force is not at the exact frequency. It is a rule of thumb that when you design rotating equipment you want to stay 25% below or 25% above the natural frequency so that you would not excite it (wake it up). Looking at the 50 - 80 mph speed range, if we take the mid point 65 mph as the natural frequency, then 25% less is 49 mph and 25% more is 81 mph. 50-80 mph speed range being noisy fits pretty well to the 25% rule, doesn't it? So the question is if the humming noise is loudest at around 65 mph speed?

So, what I would do is to change that center bearing while taking the drive shaft out for replacing the U-joint bearings and balancing it. And replace those flex disks too. That center bearing is a very low cost part (ball bearing) and as it needs to be removed for the shaft work there is no extra labor putting a new bearing on when re-assembling it all.

The humming noise very often is caused by a U-joint that needs new bearings. And it has been said in earlier posts that the sound could feel like it is coming from the front of the car while it is caused by something under or in the rear of the car. This is because we are dealing with the cars body vibration, which means the vibration excitement can be in a very different location from where the actual natural frequency vibration takes place.

nc211

Very interesting Arrie, thanks! We did look at the driveshaft and inspected the couplings and bearing, nothing seemed out of bounds on either of the 3 components. We might go there next though if this current attempt doesn’t fix it. If none of that works, then I’m afraid it’s probably in the transmission indeed, likely the transfer case bearings. I don’t think I’m willing to go down that road though on cost to repair. Hundreds, I can handle. Thousands, is a debate between how much I like the car and how much I might like something else instead. We’ll see what happens here.

I did hear that my front diff is leaking from two spots and not just one. The pinion seal is bad, and the axle shaft seal is bad. So there is no telling how much has leaked out at this point. I don’t think s lot of gear oil goes into the front diff, so it might be meaningful... we shall see!