G-Tech Article  

Axle Service - Front

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posted by Dave Gomes on 2003-07-15
Updated on 2003-12-14

This article covers removal and replacement of brake calipers, rotors, wheel bearings and seals, kingpin bearings, swivel ball seals, CV joints, axle shafts, and tie rods. If your steering is less than perfect, consider some or all of the service elements in this article.

For a parts list, see the "Wheel Bearing Service Parts" in the "Related Items area of the left hand menu.

(1) First park the vehicle on a level surface, chock the rear wheels and secure the parking brake. Then raise the front axle and place securely on jack stands. I always like to get some help with the heavy work.
(2) A 19mm socket and impact wrench make short work of the wheel bolts.

(3) Next we'll use a screwdriver to pry the brake pipe securing springs up and out of their slots in the brake line fittings. This will give us a little room to move the lines around to get at the upper swivel pin bolts.
(4) A breaker bar, 3-inch extension, and a 17mm socket remove the two swivel pin bolts that hold the brake pipe mounting plate.
(5) A normal 19mm socket can remove the upper caliper bolt. But for the lower one, we'll need a modified socket to fit into this tiny space. You can improvise with a cheater bar over a high quality 6-point box end wrench, if you have one that will fit in there. But a socket works really well with just a little modification. Once the caliper is removed, I used a piece of 3/16 brake line about 8" long and bent into an "S" shape to hook through an extra hole in the inner fender well and hang the caliper there up out of the way and not stretching the brake hoses.

(6) To get at that tricky lower caliper bolt, I bought a consumer grade socket and faced off the open end until the socket was just deep enough to fully accept the bolt head. This one is a 12-point socket. If I'd been able to find a 6-point I would have bought that, but I was at Home Depot when I remembered it and the only 6-point 19mm sockets they had were part of impact sets. So I bought this one for about $4. It worked fine.
(7) An impact screwdriver works really nicely if the rotor lock screw is stuck. Striking the rear of the driver simultaneously seats the bit into the screw and rotates it counterclockwise to loosen the screw. At re-assembly we'll take precautions to prevent these from sticking in the future.
(8) Work a screwdriver in various places around the grease cap to pop it loose.

(9) At this point you'll need a pin-socket to remove the hub nuts. You can make your own from a suitable donor socket using a grinder, or fancier tools if you like, or you can buy the socket from Mercedes. If your hub nuts look pretty buggered up and you choose not to re-use them, you can even get them loose by hitting a pin punch or blunt chisel against the flats of the slots to drive the nut in a counter-clockwise direction. There are two types of hub nuts fitted to 460s. An early type that has slots approximately 8mm wide, and a later type nut that has slots approximately 6.5mm wide. Only the later type nut is available as a replacement, so if you're thinking of buying the MB socket, buy the one for the newer type nut, and buy a set of new nuts. The socket will work to remove the older nuts, but it will bugger up the slots pretty good. The MB socket that fits the NEW nuts is 460.589.02.07.00. The one that fits the old nuts is 460.589.00.07.00. This one also fits the diff pinion nuts, but as I said, the new style wrench can be used in a pinch. If you want to make your own socket of either type, CLICK HERE to see a sketch from our friend Roly in the UK.
(10) When I removed my right front hub, this is what I found!
(11) Daddy, what are those words you're saying?

(12) My left front hub is on the left. The grenaded one is on the right. I really don't have a clue what caused this, other than perhaps some latent flaw in the original material. The bearings were all in fine shape, with no signs of excess heat. My only clue something was wrong was that my brake pedal had longer travel due to the rotor moving around a bit and pushing the caliper pistons back. When I originally took the wheel off, I didn't even notice any excess play in the bearings. Anyway, I'll order two new hubs and save the one on the left for a spare. I don't have a picture of it, but now is the time to use a 10mm wrench to remove the three screws holding the splash guard to the swivel housing and remove the splash guard.
(13) Tie rod ends can be separated now by first pulling the cotter pins, then removing the nut with a 22mm socket, and finally, using a suitable puller to pop the ball joint free of the steering arm. This job needs to be done twice on the passenger side, and once on the driver's side. The puller shown here is part of a set available from The Tool Warehouse BY CLICKING HERE
(14) Here's the joint all freed up. Check the rubber boot for cracks. If it's cracked, the joint will deteriorate very quickly and steering play will result. Depending on your model, you may be able to replace the joint, or be required to buy a whole new rod. But in any case, the boots are not available as separate pieces because they're swaged in place.

(15) Next use a wire brush to clean up the back side of the swivel housing and remove the bolts that hold the seal retainer in place. I think it's a 10mm agian, but may be a bit larger.
(16) Now we can remove the remaining bolts holding the upper swivel pin in place (17mm socket, remember), withdraw the pin upward, and angle the swivel housing downward and off the swivel ball. Or if you prefer, you can remove the lower pin (also 17mm socket) at this time as well and pull the housing straight outward. In any case, when you remove each swivel pin, be sure any shims between the pin and the housing are kept with the pin. You'll want to re-use these in the correct places at re-assembly.
(17) I chose to wait and pull the lower pin after the swivel housing was off. In this picture I've also scooped the grease out of the housing and done a cursory job of initial clean-up of the inside of the housing.

(18) If you have just the right size socket, (I hear a 1" impact socket of Snap-On brand works great!) you can knock a hole in the upper swivel bearing inner closing plate, and use a drift against the socket to drive the lower closing plate and bearing race straight out. My Craftsman socket was a little small, so I had to use other means.
(19) That means using a long drift and striking it from the top to catch the edge of the bearing race and drive it out. No matter how you slice it, this job gets more challenging as you need to drive upward to push the upper bearing race out. But, with some perseverance, all can be accomplished without the need for the special MB tools. This will complete the disassembly of the front axle and we can move on to refurbishing and replacing parts.
(20) With the swivel housing in a bench vise I'm using a seal puller to remove the inner wheel bearing seal. This can also be accomplished by using a drift inserted from the opposite side to drive the bearing inner race against the seal and push both parts out together. But the seal puller works really well for this one.

(21) For the outer seal, my puller doesn't work so well due to the large diameter of the seal. For this one I ended up using a drift from the far side to knock the seal out.
(22) The drift can be used again to catch the inner edge of each bearing race and drive it from the housing, working your way around the whole perimeter of the race a few times to keep it running straight on the way out.
(23) Now's the time to do a thorough cleaning of the housing, especially the surfaces that mate with other parts. Remove any old gasketing and use a stone to be sure each surface is flat and free of burs or protrusions that might interfere with proper mating of the parts. Now is also a good time to clean up the backing ring and compression plate that should still be hanging on the axle with the old ball seal.

(24) Now we can start putting things back together. Here the bearing races go into the swivel housing using a brass drift and once again, working slowly around the perimeter of the bearing to keep it going in straight.
(25) I switch to a smaller drift for the last bit as the bearing race receeds into the housing, again working around the edge until a sharp metalic ring is heard all the way around, signalling that the bearing is fully seated in the housing.
(26) Now it's on to renewing the hubs. I'm using new ones here. If you're re-using your old ones, you'll need a knife-edge bearing splitter like this one available from The Tool Warehouse BY CLICKING HERE to get the bearing off the old hub, then use a screwdriver to dig out the old foam seal and clean everything up really well. Here I'm placing a new foam seal onto the hub. The face of the seal that has a small protrusion around it's outer edge should be the one facing upward. The smooth face goes against the hub. I smear this one with a little wheel bearing grease just for good measure, since it will ride against the swivel housing.

(27) Here we've packed the inner race of the outer wheel bearing with grease and we're driving it onto the hub. Use a very small diameter drift and be sure to strike only the edge of the inner race, and not the rollers or cage. Again, work your way around to drive the bearing on straight all the way to the shoulder on the hub. Be sure the shoulder is nice and clean so the bearing can seat squarely against it.
(28) Here's the hub with bearing in place and ready to go back on the car.
(29) Now we move on to the CV joints. One of mine needed to be replaced since the broken hub had resulted in damage to the threads of the outer stub shaft. And since the car has nearly 300,000 miles on it, I decided to replace both CVs with new ones. Mercedes will want to sell you a whole new axle shaft for nearly $1,000. But the joints are available for about $250 each from our friend Franco in Germany BY CLICKING HERE. Be prepared to speak German and transfer funds by wire, since this fellow speaks no English and doesn't accept US credit cards. Anyway, the idea here is to spread the ends of the circlip apart and slide the CV joint off the shaft. This task proved beyond my ability. When I asked Marc at Europa, he said they usually use two people, one to hold the clip open and one to drive the joint off the shaft with a drift against the center spider of the joint. I didn't have help handy, so I dropped the shafts off with my local MB mechanic and he removed the joints and replaced them with my previously procured new ones for about $50.

(30) Here's the new joint in place and the boot secured with it's inner clip. Do a little test-fiting to determine the exact location to secure the boot to the shaft. You want it far enough from the joint to give full range of motion without the joint fouling th boot, but you want it close enough to the joint that it doesn't hit the swivel ball when the shaft is inserted in the axle tube. A little fiddling will get it right.
(31) Two packets of grease came with each CV joint. I squeezed one packet into the spaces of the joint itself.
(32) I squeezed the other packet inside the boot before fitting the boot to the outer race of the CV and securing it with the outer clip and wiping the outside of the assembly free of grease. I don't want any stray grease to foul the swivel housing grease. That way I'll be able to use any discoloration of the white grease in the swivel housing to indicate a broken CV boot.

(33) Finally it's back to the axle. Here we've inserted a new closing cover, bulge toward the axle centerline, and new outer race for the lower swivel pin bearing. Drive it home as we did the others, capturing the closing cover between the race and the swivel ball.
(34) I used a red Valvoline synthetic wheel bearing grease in the wheel bearings, and a black Moly-Disulfide grease for the swivel pin bearings. I hear there's an even better product for the swivel pins available from Wurth. For this application we want something that's very highly impact resistant, and we don't need the high heat, high speed lubricating properties of a wheel bearing grease. The swivel pins are really the same type of application as U-joint bearings and should get the same impact resistant grease.
(35) Here's the inner wheel bearing ready to go into the hub and be trapped in place by the seal shown.

(36) Use a brass or plastic drift to fully seat the seal in it's recess. It will go down slightly below the inner face of the swivel housing before you feel it come up solidly against the bottom of it's bore.
(37) Back on the truck we're stretching a new ball seal over the swivel ball. The inner diameter of the seal has a tapered surface. Make sure the taper opens outward, toward the ball surface so the seal surface will mate smoothly to the ball. Before I put this seal in place I used brake cleaner and fine sandpaper to remove all of the old hardened grease and any surface rust from the swivel ball to make a smooth continuous surface for the new seal. I didn't want the new seal to be damaged if it came into contact with an area of the ball that was not swept by the old seal.
(38) Next the seal's backing ring is twisted into place over the swivel ball by separating its two ends just far enough to work it into place over the swivel ball. The axle shaft has already been loaded here, but it could have been put in after the seal and backing ring were in place. If you have a later style axle you'll see a seal ring around the edge of the hole in the axle tube that the axle shaft passes into. If you have these seals, you should pull out the old ones and replace them with new before inserting the axle. My axles are an older style that have the seals at the differential end. So much more difficult to service that I'll ignore them for now until I have another reason to pull the differential.

(39) Now the sivel pin bearings are packed with grease and put into place in their races. I put a little extra grease into the cup formed by the closing cover to sort of "stick" the bearing in place in it's race.
(40) The white arrow shows the outer closing cover in place over the swivel pin bearing. The same is true of the lower bearing. Now it's time to slide the swivel housing on over the bearings.
(41) Once the swivel housing is in place, I clean the old shims and upper and lower pins with brake cleaner, a wire brush, and finally a stone for all the mating surfaces. The upper and lower shims are given a light coating of white waterproof grease to keep water from seeping in between the mating parts and rusting them.

(42) Here the upper and lower swivel pins have been inserted and a couple bolts fitted to secure them.
(43) Next the ball seal backing ring is fit into the swivel housing until it bottoms in it's bore. I insert the ring with it's split portion uppermost, since that part of the seal is just pivoting on the ball and not dragging across it, the seal doesn't need as much backing support at that point. Now is also a good time to coat the paper gasket for the seal retainer with some waterproof grease and stick it in place on the seal retainer. As you can see I've also coated the ball with a light coating of waterproof white grease to be sure the seal has a nice greased surface to ride on from the start and doesn't get scored by any pits in the ball.
(44) It's hard to get a picture of this operation, but what I did to get the seal in place is I put one bolt into the seal retainer plate on the front most part of the swivel housing. Then I stretched the seal around the ball as I pressed the retainer plate in closer and closer to the housing on the side closest to the camera here. Eventually I could place a second bolt in the retainer ring 180 degrees off from the first one. Be careful to be sure the tapered edge stays against the ball and that the seal doesn't twist as you stretch it around. Once that second bolt is in, you can put in the rest of the bolts and tighten them all up evenly around the perimeter of the seal.

(45) Now it's about time to replace the tie rods. Before you put them in place, you can help them out a little if you fit a needle attachment to your grease gun and squirt some grease up inside the boot. Place the needle against the ball joint shaft and slide it along the shaft up under the boot. Be careful not to damage the boot. 4 or 5 squirts of grese now will help those joints last just a little longer. Again, this is a u-joint type grease.
(46) Slide the ball joint shaft in place, replace the nut, tighten with 22mm socket to the first time a slot aligns with the cotter pin hole AFTER you've reached about 90 Nm, and insert and bend a new cotter pin.
(47) Use a 17mm socket to torque the lower swivel pin bolts evenly to 160 Nm

(48) Use a 17mm socket to torque the upper swivel pin bolts evenly to 120 Nm
(49) Replace the splash guard
(50) Slide the hub in place after coating the splines with a bit of high-impact grease.

(51) Fit a new hub nut with the conical face toward the hub and the flat face outer-most. Tighten the inner hub nut as far as possible while rotating the hub. This is only to hold the hub in place, actual torquing will be done later.
(52) Fit the rotor in place and secure with the philips head screw. I used a little copper-based anti-seize brake grease on the scew before I inserted it. I put a fine coating of grease on both the threads and the tapered face of the head of the screw to keep either one from seizing up as the rotor is heated and cooled.
(53) Here's a picture of the "Coppaslip" brand grease I used above. Here I'm also using a bit on the upper caliper bolt, the one that doesn't have the loc-tite factory applied. These bolts get tightened to an awful high torque. I want something in there to protect the threads and keep any water from getting in to weaken the bolts or seize the threads. It's recommended to use new bolts for the brake caliper attachment, and I have to agree. These bolts can be twisted or weakened without showig outward signs. And with such a mission critical safety item as the front brakes, don't take any chances.

(54) Here we remove the two forward upper swivel pin bolts to prepare for the placement of the brake pipe bracket.
(55) Remove the caliper from it's hanger and slide it into place over the rotor and against the back side of the lugs on the swivel housing. Don't forget to remove the hanger hook from the inner fender or you'll hear it jingling around later.
(56) Here we place the upper caliper bolt. This is the easy one to get to.

(57) I found the lower one impossible to reach, even with the shortened socket, so I started it with an open end wrench.
(58) Then spun it in most of the rest of the way with the "GearWrench" brand ratcheting box end wrench. These things are worth their weight in gold in tight areas. And the G front axle job has no shortage of those. The 10mm version was especially useful on the ball seal retaining plate on the back of the swivel ball.
(59) And finally we're able to reach in with the shortened 19 mm socket for the final torquing to 260 NM for the lower bolt and 200Nm for the upper one.

(60) We're in the home stretch now. It's time to fill the swivel housings with grease. I use the 19mm GearWrench to pull the plug from the housing. Remember to have the wheels turned all the way AWAY from the side you want to add grease to.
(61) Three squeeze tubes of Lubriplate's Special waterproof Marine Grease will result in just a slight overfill of the housings, even considering that some of the grease will squeeze out around the filler hole. These tubes are 10 oz. each. Two regular grease gun tubes at 14 oz. each give a more accurate fill ammount, but I didn't want to do all that pumping of the gun, and a little extra grese in there doesn't hurt anything at all. So in go the three tubes of grease and we replace the plug.
(62) Don't forget to replace the two upper swivel pin bolts with the brake pipe retainer plate in place, torque to 120 Nm and re-clip those brake lines.

(63) I find it easiest to do the hub nut torquing with the road wheel in place, so here it's been re-mounted using the 19mm socket and breaker bar on the wheel nuts. Spin the wheel while tightening the inner hub nut. Wedging the toe of your boot under the tire will give you enough resistance to torque the inner nut to 200 Nm. Then without disturbing the wheel, back the hub nut off to slack, re-tighten it finger tight, and back it off 1/8 turn from there.
(64) Fit the tab washer and be sure the center tab fits down into the groove in the outer stub axle shaft. Coat the threads of the stub axle witha bit of anti-sieze to help them stand up to the high torques they'll see.
(65) Here you see why I had to tap the tab in to the slot in the last picture. I think Travis sent me the wrong tab washers. I'm not sure, but these new ones (on the right in the picture) are definitely bigger in each feature than my old ones (left in picture). They barely fit into the hub and make it difficult to bend the tabs. But I wanted to get it together, and these worked okay, so I didn't send them back.

(66) Place the outer hub nut with it's flat face against the tab washer and tighten it to 200 Nm. Then bend the tab that most closely aligns with a slot in the outer nut into place in the slot to secure the outer nut.
(67) And finally, tap the grease caps into place on the hubs. Some books say to pack the cap with grease, but I really can't see why since this cap is the farthest thing from any greasable bearing. My caps had old grease packed into them, so I left it out of pure laziness. About the only grease of value here would be a little waterproof grease smeared around the lip of the cap before installing it to keep water out of the hub nut area.
NOTE: The hub nut torquing instructions above presume new nuts on new threads. If your threads or nuts are worn, it may be advantageous to back the inner nut off more than 1/8 turn - more like 1/6 turn - before fitting the tab washer and outer nut. When finished, the wheel should spin freely, but exhibit no perceptible shake or wobble when the wheel is grasped by the outer edge of the tire and shaken in and out. To double check that the bearings aren't too tight, drive the car 20-30 miles making an effort to use the brakes as little and lightly as possible. After rolling to a stop, again using the brakes as little as possible, get out and touch the raised portions of the wheel hub that stick out beyond the rim with your fingers. They should be cool to the touch. If they're heating up with normal driving, the bearings may be too tight. But remember, use of the brakes will warm the hubs up quite quickly, so take this into account.

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