"Wheel Bearing Tour":
5-8-09 Part No. Correction (inner rear seal should be #001 997 3446 thanks Erick M.) text corrected
Additional information added 11-26-05, 11-28-05, 11-24-08
This topic will be updated and added to over the next few days since it is somewhat lengthy. I will keep adding to this first post by editing, so that the material remains together in one post and at the top of the page. Feel free to add information or ask questions anytime during the tour. We have taken many detailed photos and have diagrams and illustrations to add also.
We were unable to perform the procedure during the Ohio Tech Session, we ran out of time. Bob Fellows 1969 dark blue original 280SL was on hand for the work. Jim Villers was kind enough to contribute the bearing which he carried to the Tech Session as a spare. Thanks Jim!
Symptoms:
You may notice a low pitch groaning noise coming from the rear axle area.
Diagnose by:
Drive the car down the road and swerve from side to side. As the car leans to the side with the bad bearing the noise will increase. As the car leans to the other side the noise may disappear or become less.
Parts needed:
(1) right side axle wheel bearing "roller cylindrical bearing" #000 981 152
or
(1) left side rear wheel bearing "ball bearing" # 001 981 1525
(1) seal and gasket kit # 111 586 0035 which includes the following parts or can be ordered separately:
(1) inner oil seal # 001 997 3446 (correction 5-09)
(1) outer oil seal # 001 997 4746
(1) paper gasket # 110 997 47 46
(1) lock plate # 183 353 0373
(1) special grooved nut (optional, but comes in the kit) #153 357 0026
(2.5) quarts of 90w or equivalent gear oil
(qty) bearing grease (synthetic best)
Special Tools:
(1) 14mm drain plug tool or equivalent (a 9/16" allen wrench will work or use a 14mm bolt head in vice grips)
The BBB advises use of a special puller and a special "grooved nut tool" however These items are expensive and not needed. Depending on how tight the bearing is on the axle shaft after removal you may need to take the axle to your local NAPA store or automotive machine shop to have the wheel bearing pressed off. However there is also a simple method which you can use which will work most of the time. To install the new bearing, no special tools will be required.
To perform the work you will need two jack stands, an oil drain pan and a jack.
Here are diagrams, the 230SL has drum brakes so we have no photos of its brke assembly, but the basic procedure is the same except for the brakes. I will try to fill in some 230SL specific information as we go along.
Download Attachment: 250SL, 280SL.JPG52.24 KB
Download Attachment: 230SL.JPG76.98 KB
This swing axle differential has two oil seals on each axle The inner seals isolate the differential 90W oil from the wheel bearings which are packed in bearing grease. The outer seals keep the bearing grease from getting into the brakes.
The right side of the swing axle must be able to hinge with the suspension and the right side wheel bearing is a special barrel shaped "roller bearing" which can actually hinge with the axle.
This right side wheel bearing is three or four times more expensive than the left side "ball bearing". Fortunately since "roller bearings" are designed to handle higher loads than a standard "ball bearing", this expensive right side "roller bearing" seldom fails. View the photo below;
Download Attachment: bearing types.JPG31.02 KB
Since the rear wheel bearings are isolated from the differential oil, running the car with a low oil level in the differential will not normally cause these bearings to fail. Long term storage, dried out bearing grease, and normal usage may eventually cause a bearing failure. If left in use the bad bearing may seize and may begin to spin inside its seat in the axle housing, wearing the casting itself.
As typical, Bob's left rear "ball bearing" began making some noise which progressively became more noticeable. We did the "swerve test" which confirmed our diagnosis.
Download Attachment: rear wheel1.JPG49.34 KB
The first step is to place the rear of the car on jack stands and support the rear axle so it is as level as possible.
A 14mm drain plug tool is used to remove the drain plug at the bottom of the differential casting, allowing the 2.5 quarts of gear oil to drain.
Download Attachment: drain fluid 2.JPG49.51 KB
The rear wheel is removed and the brake caliper can be unbolted and hung out of the way without opening any brake lines. The brake disc can now be removed. In the case of a 230SL the rear drum is removed. The 230SL drums have three threaded holes on the flat side of the drum. Winding three M6 bolts into these threaded holes magically removes the drums.
Unfortunately on the 230SL drum brakes the wheel cylinder must be disconnected to remove the backing plate.
Disc brake cars have a complex emergency brake arrangement, while drum brake cars have the usual complexity of springs and shoes. Pay special attention to the arrangement in either case.
Disc brake cars have two large holes in the axle wheel hub so the spring retainers holding the emergency brake shoes in place can be removed. Needle nose pliers or small needle nose vice grips can be used through these openings. An old screwdriver can be modified to work as a simple removal tool also. In any case the axle must be stripped of it's brake and emergency brake assemblies.
Download Attachment: retainer 3.JPG59.35 KB
The brake backing plate or beaing retainer is held on by six 13mm nuts around the axle. These can be removed using a socket through the holes in the axle hub.
Download Attachment: axle4.JPG61.48 KB
Drum brake cars will also have to have the two 10mm nuts holding the emergency brake pulley assembly (#20 on the 230SL diagram above). An additional 14mm bolt (#2 on the 230SL diagram) also must be removed behind the brake backing plate on the drum brake cars.
The axle should be ready for removal at this point. In place of the expensive special axle puller, bolt a piece of angle iron or uni strut to the axle and tap it out with a hammer (see below).
Download Attachment: axle removal5.JPG56.1 KB
Download Attachment: axle out 6.JPG50.72 KB
Remove the axle assembly with bearing. Confirm the diagnosis by slightly pinching the bearing in the jaws of a bench vice and turn the axle. The slight pressure of the vice on the bearing will simulate normal load on the axle. You will feel a definite flat spot on the defective bearing as the axle is turned.
Download Attachment: vicetest7.JPG60.26 KB
A special "grooved nut" holds the bearing in place. The grooved nut is locked in place by a lock plate which is bent up into the grooves of the nut. Grind a punch so as to fit the groove and straighten the lock plate enough to release the grooved nut.
Download Attachment: axle 8.JPG40.7 KB
The grooved nut can be loosened by use of a special tool, or a spanner wrench, flat drift or even a pipe wrench.
Download Attachment: grooved nut 9.JPG35.82 KB
The axle bearing must be removed next. The BBB shows a very special and expensive puller, your local NAPA or automotive machine shop can press it off. I use another simple trick. Place a block of aluminum or hardwood on the floor. Strike the axle assembly splined end down firmly on the block. With one or two blows the bearing should pop off, (see photo). This method has worked many times for me. Do not use anything harder than aluminum or wood or you may distort the end of the axle.
Download Attachment: [ removal 10.JPG67.58 KB
The old axle seals can easily be removed next. The inner seal located in the axle tube can be tapped with the drift by hitting it inward in one spot so it will twist so it can be pulled out.
Download Attachment: inner seal 12.jpg62.44 KB
The next photo shows the installation of a new seal using a large socket to drive it in place. I coated the outer surface of the seal with gasket shellac to insure a good leak proof seal against the axle housing.
Download Attachment: install seal 13.jpg60.18 KB
The outer seal located in the backing plate can be tapped out on the workbench.
Find a correct size socket or pipe to drive the new seals in place. Also coat the outer seal surface with gasket shellac to insure a good leakproof seal against the housing. Coat the soft seal lip with some grease so you do not have a "dry" start up. Starting the new seal in straigth is the challenge here.
Download Attachment: outer seal14.jpg58.28 KB
The bad bearing can vibrate or actually spin in the housing, wearing away it's seat. A highly polished suface in the housing can be a sign of bearing rotation in the housing. You can tap a series of punch marks arount the circumference of the housing and also use "Locktite Stud and Bearing Mount" or equivalent to insure a good snug fit for the new bearing.
Download Attachment: housing16.JPG45.6 KB
Download Attachment: housing17.jpg59.43 KB
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Emergency Brake information (disc brakes)The emergency brake assemblies on the disc brake cars can often be the most troublesome part of the bearing change. I have some information and photos here which may help you next time. I will add this information to the tour also.
Here is a photo all the emergency brake parts;
Download Attachment: exploded view.JPG
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This photo shows a backing plate with the parts installed. The adjuster can be installed in either direction so take note which way it is pointed for re-assembly otherwise adjustment may be backwards but will work fine.
Download Attachment: clear view.JPG
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Two special tools will make the job quite a bit easier. One can easily be home made, the other is an inexpensive spring tool. Grind a round screwdriver shaft or similar for the home made tool.
Download Attachment: special tools.jpg
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Use the home made tool to release the retainer springs first. Push in then do a quarter twist to release. The retainer spring hooks through the hole in the backing plate see photo of the back view.
Download Attachment: removal of retaining springs.jpg
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Download Attachment: back view.JPG
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After both retainer springs are removed use a large screwdriver to pry the top brake shoe far enough to remove the adjuster. this will loosen up the entire assembly enough so that you can remove both upper and lower return springs with the spring tool.
Download Attachment: remove adjuster.jpg
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Both emergency brake tools can now be remved. Next remove the cam assembly by pushing the connecting pin out.
Download Attachment: removal of cam unit.jpg
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There is a special "C" clip which must be removed before the emergency brake cable can be dis-connected from the backing plate.
Download Attachment: removal of emergency brake cable.JPG
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Continue the axle removal by unfastening the 13mm nuts around the axle.
My re-installation of the emergency brake assembly is the reverse order of above. I prefere to deviate from the factory assembly sequence in that I install the brake adjuster and top return spring last instead of first.
More to follow soon!
Joe Alexander
Blacklick, Ohio
