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  #1  
Old 03-25-2014, 12:51 AM
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300SD Wheel hub humming

I swapped the front wheel hubs/rotors from my 85 300TD into my 83 300SD a few years back, and since then (without realizing the cause), heard a light humming/thumping noise in my front driver's wheel/hub. On a recent road trip, the inner bearing disintegrated and I had to tow the car home.

I suspect now that I tightened the spindle locking nut TOO tight. When free spinning, the wheel definitely slowed down pretty fast, like there was serious resistance. After maybe 2 years, some noises coming and going, the bearings became stressed enough to the point of breaking (especially when the other wheel moved more freely). I'm wondering if someone can confirm this possibility.

I was wondering if there's anything special involved with putting the new bearings on the hub. I tried doing it the other day with simply using the locking nut and hub as a "press" to fully tighten the hub and bearing, then backed off on the locking nut until it rotated as freely as the other wheel. I drove it for about 60 miles and it definitely sounded differently than before, but it still sounds like a light low humming noise. Maybe that's normal to an extent.

Is there anything special to the process of adjusting the locking nut or getting the bearings on?
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  #2  
Old 03-25-2014, 01:22 AM
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Quote:
Originally Posted by tomas_maly View Post
Is there anything special to the process of adjusting the locking nut or getting the bearings on?
If you are not measuring the bearing preload with a dial indicator, you are just stabbing in the dark. And you have already demonstrated how that works out.
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  #3  
Old 03-25-2014, 03:03 AM
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https://www.youtube.com/watch?v=lI5GopJIBIA


This guy does it just by hand/feel. Is he an idiot? No dial indicator that I saw.
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  #4  
Old 03-25-2014, 05:14 AM
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Quote:
Originally Posted by tomas_maly View Post
https://www.youtube.com/watch?v=lI5GopJIBIA


This guy does it just by hand/feel. Is he an idiot? No dial indicator that I saw.
Well I don't think it is fair to say he is an idiot but that's not the way to do it by the book.

As for a bearing disintegrating - the correct pre-load / clearance and the right amount of grease is important but as you took the hub off of one spindle / axle and put it on an other it is important to make sure you keep the bearings with each hub => bearings wear into their races - at CSI levels of examination they are more or less unique - you should always change the race with the bearing. If you swap used with used the chances of failure are greater.

In terms of a W123 / W126 front wheel bearing this means the outer bearing races in the hub should be changed if the bearings have been mixed up.

If the visible outer bearing races are damaged at all I have found that if you destroy the tapered roller bearing and look at the inner race you will often find more damage there - dirt / debris / muck seems to get trapped in the inner part of these tapered roller bearings more than it does on the larger outer bearing race surface.
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Old 03-25-2014, 07:53 AM
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Whatever works.

My first MB needed this guy, as about a month after purchase, the RF bearing seized.

Mucho denaro later, back on the road.

I use a dial indicator. I did not replace the races, so far, so good.
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  #6  
Old 03-25-2014, 10:31 AM
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Originally Posted by tomas_maly View Post
This guy does it just by hand/feel. Is he an idiot? No dial indicator that I saw.
You also didn't see the bearing tension being relieved after the spindle nut was overtightened.

That said, I am sure that YouTube would not allow anything that was not completely correct and accurate. So, forget the FSM, grab your Channellocks and adjust away!!!
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  #7  
Old 03-25-2014, 12:32 PM
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Quote:
Originally Posted by tomas_maly View Post
I swapped the front wheel hubs/rotors from my 85 300TD into my 83 300SD a few years back, and since then (without realizing the cause), heard a light humming/thumping noise in my front driver's wheel/hub. On a recent road trip, the inner bearing disintegrated and I had to tow the car home.

I suspect now that I tightened the spindle locking nut TOO tight. When free spinning, the wheel definitely slowed down pretty fast, like there was serious resistance. After maybe 2 years, some noises coming and going, the bearings became stressed enough to the point of breaking (especially when the other wheel moved more freely). I'm wondering if someone can confirm this possibility.

I was wondering if there's anything special involved with putting the new bearings on the hub. I tried doing it the other day with simply using the locking nut and hub as a "press" to fully tighten the hub and bearing, then backed off on the locking nut until it rotated as freely as the other wheel. I drove it for about 60 miles and it definitely sounded differently than before, but it still sounds like a light low humming noise. Maybe that's normal to an extent.

Is there anything special to the process of adjusting the locking nut or getting the bearings on?
What you did is a good way to damage the Bearing becaus it puts the pressing force on the edge outer surface of the Rollers against the Bearing Race.

Not adjusting the Bearing by way of the Factory Method is also taking a chance.
The proper method using a Dial Indicator is in the DIY section:
DIY Repair Links
http://www.peachparts.com/shopforum/forumdisplay.php?f=82
http://www.peachparts.com/Wikka/DoItYourSelf
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  #8  
Old 03-25-2014, 12:59 PM
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Quote:
Originally Posted by tangofox007 View Post
You also didn't see the bearing tension being relieved after the spindle nut was overtightened.

That said, I am sure that YouTube would not allow anything that was not completely correct and accurate. So, forget the FSM, grab your Channellocks and adjust away!!!
Joking aside, I am looking through the FSM (33-300, adjusting bearing play). It mentions "remove contact spring for radio suppression"... I am honestly not sure what that is. The FSM shows a little white rectangle thing covering the spindle (parallel to the surface area), but all I see is a pin that goes through the middle of the spindle. The cut-away diagram shows what appears to be a flat clip (similar to what goes on the throttle lever), which I don't seem to have. Nothing protrudes out of the spindle.

I'm assuming you mean tension relief that the spindle being tapped with a mallet (step 5)?

The FSM seems to say to remove the "contact spring" (step 3), then tighten the locking nut until the hub is "hard to turn" (step 5), then back off 1/3rd a turn, then whack the spindle with a mallet. Let me know if I got that right (without the sarcasm)...

When it starts to mention checking for "play" it doesn't really say explicitly how to adjust that play within tolerance. I'm assuming by adjusting the locking nut either way (and relieving tension again)?
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  #9  
Old 03-25-2014, 01:22 PM
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The radio suppressor spring is a bit of spring brass(?) that is often buried in the grease in the axle cap.

{And there's nothing wrong with a bit of friendly sarcasm in my honest and most humble opinion - take it as a friendly poke in the ribs from a buddy with a friendly glint in his eye}
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #10  
Old 03-25-2014, 01:30 PM
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Quote:
Originally Posted by tomas_maly View Post

I was wondering if there's anything special involved with putting the new bearings on the hub. I tried doing it the other day with simply using the locking nut and hub as a "press" to fully tighten the hub and bearing, then backed off on the locking nut until it rotated as freely as the other wheel. I drove it for about 60 miles and it definitely sounded differently than before, but it still sounds like a light low humming noise. Maybe that's normal to an extent.

Is there anything special to the process of adjusting the locking nut or getting the bearings on?
yeah...
firstly, the bearing has two parts, and the outer race needs to be swapped to the new one. are you doing that? the old race needs to be hammered out, with a brass drift or steel pin PRECISELY tapped out, then a race installer needs to be used to fully seat the new races...
after the races are set, THEN the FULLY GREASED bearing sets need to be set in, then the grease seal set flush, then the hub set on, and the spindle nut tightened fully, and the hub spun by hand a few turns both directions, then the nut loosened, and finally the extremely precise end play needs to be set with a dial indicator...

can it be done by feel... sure it's an extreme remote possibility that a highly skilled experienced mechanic could do it... does that sound like you?
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  #11  
Old 03-25-2014, 04:37 PM
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Quote:
Originally Posted by tomas_maly View Post
Joking aside, I am looking through the FSM (33-300, adjusting bearing play). It mentions "remove contact spring for radio suppression"... I am honestly not sure what that is. The FSM shows a little white rectangle thing covering the spindle (parallel to the surface area), but all I see is a pin that goes through the middle of the spindle. The cut-away diagram shows what appears to be a flat clip (similar to what goes on the throttle lever), which I don't seem to have. Nothing protrudes out of the spindle.

I'm assuming you mean tension relief that the spindle being tapped with a mallet (step 5)?

The FSM seems to say to remove the "contact spring" (step 3), then tighten the locking nut until the hub is "hard to turn" (step 5), then back off 1/3rd a turn, then whack the spindle with a mallet. Let me know if I got that right (without the sarcasm)...

When it starts to mention checking for "play" it doesn't really say explicitly how to adjust that play within tolerance. I'm assuming by adjusting the locking nut either way (and relieving tension again)?
The Spring they are speaking of is sort of V shaped and goes in the Hub Cap between the Hub Cap and the Axle end. Mine were long gone when I got the Car and I never replaced them and had no issues.

You are tightening the Lock Nut till it is hard to turn to squeeze the Grease our from between the Bearings and the Bearing Race (why you also need to rotate the Hub). The reason for squeezing the Grease out is that the Grease can throw the Dial Indicator reading off.

Because you over tightened the Nut to squeeze the Grease out it is possible for the Hub to sort of get suck there. So they want you to back off the Nut and smack the end of the Axle with a Mallet to release it so it is free to move again.

People have shown a Rubber Mallet but I think a Mallet with hard Plastic ends would work better.

The instructions in the Mercedes Manuals are sometimes lacking due to Language translation issues and the fact that the Manual was actually made as a guide for Mercedes Mechanics and not for us unskilled DIY Folks.

Another issue is that sometimes the Manual has how to check something and you need to read down further in the instructions on how to set-up something after you did a replacement and you finde that there is more detailed instructions there.
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