I have a rear noise that sounds like a wheel bearing. I took it to the independent to have it checked out and he said the left rear was loose. I told him to replace the bearing and when he got it apart it everything looked ok. The noise has been getting worse or I’m just aware of it more. (About 5-6K )He said the hub was bad . Has anyone replaced rear wheel bearings? The outer race was still on the hub but the inner race was apart. Where the inner race is pressed to the hub… the hub has a grove… not flat and smooth like you would expect. It could be the casting because the old bearing does not have any scoring. I don’t want to replace the hub for 130.00 if it is not necessary. Is anyone experienced with rear bearing and understand what I’m talking about. Your input would be appreciated

Yes, the inner race usually sticks to the hub. The race comes off and you reuse the hub. I don't know why they want to replace it, It's just a chunk of highly machined steel and should be reused. Only time I've replaced one is if it's damaged because the bolt holes for the wheel bolts were stripped/damaged beyond repair. Is the shop familiar with Mercedes? There are several ways to remove the inner race, the "Mercedes way" is to use a collet puller, this is the "nicest" to the hub (also called the flange). There are other ways, which admittedly are more popular, including making a lateral cut to the race with a grinder then prying it off, and also applying heat to it so it expands slightly and taping or prying it off. I like the collet puller, if you have it it's fast, easy and no real possibility of damaging the hub.
Could it be the hub was damaged during removal and now they say the hub is "bad" and needs to be replaced?
Or am I misinterpreting the whole question and y the bearing was replaced 5-6,000 miles ago, and now they say the problem is the hub? THAT would be a little too weird for me. If they try removing just the hub to replace it (for whatever wild reason) that inner race will MORE than likely come off with the hub again and it'll need a new bearing AGAIN.
Gilly

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Hello Dan,

The Tec has the tool and works on mercedes/bmw He said he never saw a rear bearing go on a 300e... and never replaced one.

I wanted to see what was making the noise so after he got it apart I was expecting a dark blue bearing or some sort of scoring. I looked at the flange and where the bearing race rides there were groves. Is that normal? Looks like the race only rides on 1/16 of a inch on each side with a grove in the center… OR what the tec thinks is the bearing went and was turning on the flange causing the grove. The bearing was replaced and not the flange. The grove is not scorn like something was spinning on it. Could that grove be normal? I have only had the car for 6 months about 8K.

Joe:
It's not all that unusual for a rear wheel bearing to need replacement on a 124, this guy must be lucky or just not work on many.
I'm sorry I'm having a difficult time comprehending what you are describing and also totally lost on the series of events you are describing.
1. You wanted to see what the noise was.
2. The tech took apart the rear hub, the inner race of course stuck to the flange.
2a. Did the bearing get replaced, yes or no.
2b. If it did, was this the 5-6K miles ago you mentioned? yes or no
3. The area on the flange where the bearing (inner race) presses on has grooves. Is this normal you ask. Maybe. There may be some scoring depending on how the inner race was removed from the flange. I would expect them to be across the narrow end of this area, not scores "around" the area as though something were spinning on it. This is a tight fit. If the bearing locked up, and the flange were spinning on the inner race, i assume you sure as heck would KNOW something ain't right. Never seen/heard of this happening before.
4. Looks like the inner race rides on 1/16" area. No, the area is about the width of the one section of inner race that is left on the flange after removal, about 3/8" to 1/2" by my estimation. It's flat, no machined in groove or anything.
4a if the groove is as you described "across" the area of the flange that the bearing is pressed onto, the tech may have used the method of inner race removal that I mentioned where a slot is cut into the inner race section to loosen the races grip on the flange, then is quite easily pryed off. Some techs I've seen do this twice on opposite sides of the old race, then it just falls off. i don't like marking up the flange with the grinder, so i use the collet puller, but i don't think that the slot that usually is left on the flange really hurts anything, nothing that would make a noise.

IF I had to guess or present a possible scenario, taken from personal experience, here it is:
Bearing is reinstalled, tech forgets to install the big retaining clip for the bearing, only discovering it AFTER the flange is reinstalled.
Tech tries to remove the flange from the new bearing, oh crap, the inner race popped out, stuck to the flange. Tech Carefully removes the inner race, pounds inner race into new bearing, installs big circlip, reinstalls flange, etc. Been there, done that, except the bearing is now junk and has to be removed, sorry boss, we just bought a wheel bearing. I'm sure several techs reading this can relate.
Not saying that this is what actually happened, but it can happen. If you work at a dealership you tell the boss you're sorry and move on. If it's a smaller shop the tech and/or owner may have different ideas. MAY is the key word, I don't want to generalize, this could happen in a big shop too if the tech thinks he's been screwing up too much lately and is afraid of the consequences of "one more" screw-up.
Whew, I'm done
Gilly

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Thanks for your patients Dan… The car is at the shop now. Apart waiting for a new flange. It was 3pm on Friday and the part was not available. The next generation of forums should have a FORUM-CAM that would make it easy.

I think you answered my question. The new flange without any bearings should have a smooth machined surface from the hub part to the spine for the new bearing races to rest.
There are no groves under the races. I’ll let you know how it turn out Thanks again

OK Joe, no sweat. One thing I'd like to mention is that if he's replacing the flange he should be doing the bearing too. As I mentioned, the inner race almost always comes off when the flange is pulled, and even if it doesn't I'd still be leery of reusing the bearing, as the removal of the flange will still put a pretty good side load on the inner bearing race, which could lead to problems later on. Doesn't matter that the bearing was already replaced, I'd have him put a new one in, just wouldn't trust it.
Also, just to touch on something else you mentioned (oh boy, here we go again) . On the inner part of the flange, the side that faces the inside (the half-shaft butts up against) it seems to me there may be a circular groove there. I didn't realize it at the time, but we may be talking about 2 different areas of the flange. I thought you meant the area the inner race presses onto. No grooves there. But yeah, if you have the flange sitting face down on a table (the face being the part the wheel bolts to) and looking at the splined part that the half shft splines fit into, there may be a groove running around that splined hole, just going by memeory. Never paid too close attention to it though.
Gilly

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this grove your are talking about would not be where the second race goes would it...

Joe:
Nope. The splined end of the half shaft would butt up against this groove. Not the splines themselves, they go into the flange. There is a "stop" on the inside of the splines, towards the outer CV joint, that butt up against the inside of the flange, it's what the bolt or nut (usually a nut but later on they had bolts, depends on the halfshaft) tightens against when securing the half shaft to the flange.
Gilly

ps The stub-end of the half shaft, the one that goes though the bearing and hub, doesn't fit as tightly into the inner half of the inner race like the flange does, the flange is a press fit. That's why the inner race usually sticks to the flange but not the stub-end of the half shaft. When you remove the half shaft nut, usually just a few raps with a plastic hammer will release the stub end of the half shaft from the center of the flange.

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I think I know what he's talking about here...

On my 87 300E the RR bearing was obviously bad. Got the bearing, pulled the carrier w/ hub flange and took it to a shop to have the old removed and the new pressed in.

Where the inner races (2 pieces here) ride on the hub flange we found that the inner (towards car center) 1/2 of the inner race had spun on the hub flange and wore it down some. Not good.

Now I'm waiting for the new hub flange to get here so I can get it back together.

A few months ago I had to do the LR (second time) and the hub flange was good. The car has 267, 000 mi., so I can't really complain.