Help!! Rear Half Shaft Installation - PeachParts Mercedes-Benz Forum

zeiglerr · #1 03-21-2009, 12:16 PM

I broke a rear half shaft last week and got a replacement VERY fast from Phil. The old shaft came off easily (2 parts!) but I'm having a tough time getting the new one in place. With the spline in and snugged down, the diff axel end doesn't clear the "bump out" which is about 1/2". I've pried and tugged, taken out the 2 rear diff bolts, raised the diff up and down slightly, etc, with no luck. I've worked the new half shaft in and out against the CV's to get the grease out of the way and just can't get it to contract enough so that I can get the inner hub onto the differential flange. Any ideas?? Always before the CV joints on the Half shaft had enough slack that I could press the ends in and the length would clear, then stretch back out the 1/2" or so to attach the hub. Model & year below. Thanks.

JimmyL · #2 03-21-2009, 12:43 PM

Diff side goes in first! Then raise the diff to clear the hub spline entrance. In extreme cases you can loosen the top shock nuts to drop the hub a bit more.....

zeiglerr · #3 03-21-2009, 01:22 PM

Unfortunately that doesn't work on the back end because there's no place to stick the 4" spline while you're attaching the diff end unless the tie rods are all unattached. If that was the case, I wouldn't have a problem.

JimmyL · #4 03-21-2009, 02:14 PM

Perhaps a W124 is different.......

Jeremy5848 · #5 03-21-2009, 02:39 PM

Quote:

Originally Posted by JimmyL

Perhaps a W124 is different.......

I've wondered about this too. Most of our "collective wisdom" on half-shafts is based on the W123 chassis. Given the way the diff is mounted, I've always thought that it would be a lot more work to do half-shafts on a 124.

BTW, Reid, can you give us some gory details on how the half-shaft broke? Most of us do this job to replace a split rubber boot; actual breakage is much less common.

Jeremy

zeiglerr · #6 03-21-2009, 03:41 PM

I'm going to try to move the differential over (probably have to disconnect the half shaft on the other side!!) or maybe I can drop it down enough to get the clearance I need. With the spline end in the "cage" formed by all of the suspension links on a W124 wou can't get the big end even close to the diff. and with the hub end attached there's no room to swing the spline end up, over, around all of the suspension parts to get the spline through the wheel hub. I did get an aftermarket axel $125 VS $545 for the OEM part. and I'm thinking that the OEM part would have pulled-in enough to clear without all of this trouble.

The axel break was interesting. I had a full-out emergency stop with anti-lock brakes banging because someone blew a stoplight and went through right in front of me at about 50mph. A couple of lights later, I pulled away and when the car shifted into 2nd there was a clunk and the axel broke in a spiral shear right at the small end of the left outside boot. There was some corrosion there and the car has 271K miles so it may have been a combination of metal fatigue, corrosion, and a sudden extraordinary stress.

vstech · #7 03-21-2009, 08:39 PM

OOH, I've read of the rear control arms and mount points failing on 124's be sure and seriously inspect them before you get back on the road!
do the 124 axles have any way to separate the half shalfs? some 123 shafts do... aack. good luck. post some pictures of your situation for those of us to prepare for future issues with this.

zeiglerr · #8 03-21-2009, 09:32 PM

I'll try to post some photos Sunday night. I got pulled away this afternoon and will be gone most of the day tomorrow. The suspension mounting points all look great. My plan tomorrow night is to remove the shock absorber and see if I can get a little more drop on the suspension to give me the fraction of an inch I need. Now that I think about it, I put Sportline shocks and springs on this car when I got it 11 years ago and that might be why I'm having problems - less suspension drop when the wheels are off the ground. If Obama would give ME a stimulus plan, I'd just spend the $600 per side and replace all of the tie rods, links and bushings plus the brake disks & pads and I wouldn't have to poke my head under there for another 200K miles!! (other than to replace friendly brake parts)

Billybob · #9 03-21-2009, 09:44 PM

Assuming that you have the rear suspention hanging, the spline is put into the hub and snugged in place, the diff end is then swung forward around and then upward over the differential's flange. Then the axle end can be lowered into place from above. You might need to use a large screwdriver or smaller prybar to lever the angle of the axle's end piece to get it to slide into position. You can also pull down on the wheel hub to deflect it a little further and therebye gain a little space.

If your doing this on the driver's side you need to have the exhaust hung lower off its' mounts. Make sure you use locktite on the bolts and the bolt heads are clean before putting the tool to them, good luck.

zeiglerr · #10 03-21-2009, 10:25 PM

That's where I was yesterday. I can get it to flange-on-flange but all of the prying I tried wouldn't get the "hump" on the end of the axle hub over the flange. I tried from above and the side, bending the hub as far as it would go to the side for clearance, but there's just no give in the system anywhere. That's is good, I guess. Today, I stood the half shaft on end and tapped it on a piece of wood to make sure both ends were in as far as they could go. I think it moved some grease around and gave me another fraction of an inch so I'll try again tomorrow. I'm thinking the OEM half shaft must compress in a bit more to provide clearance.

zeiglerr · #11 03-23-2009, 10:13 PM

I should have checked the new part against the old part better. The new one has the right part number (129 350 41 10) but is 14mm longer and the hub is 8mm smaller in diameter. The MB OEM part is now over $1,000 so I'm hoping the aftermarket one I got from Phil (made by GCK) was just mislabeled. More to follow....

zeiglerr · #12 03-24-2009, 11:37 AM

The problem getting my halfshaft in place was that the replacement part made by GCK was the wrong size. The MB reference number on the box is correct for this car with ASD from what I can tell (129 350 41 10) The list price for the OEM part from Mercedes is now over $1,000!! so I'm trying to find out whether the flanges on my differential were swapped when it was repaired by an indy shop a few years ago, or if GCK is using the wrong MB reference number. On the remote chance that someone has an ASD differential out of the car, or a half-shaft for one laying around, here are the size differences. It would be very helpful to know which size is correct. Thanks, Reid

.............................................Length (total length).....................Hub Diameter

My Car..................................about 658mm...............................109.60mm
(broken axle)..................................25-7/8".....................................4-5/8"

GCK Replacement.........................about 672mm...............................101.80mm
....................................................26-1/2".......................................4"

milner351 · #13 03-24-2009, 12:28 PM

keep us posted!

zeiglerr · #14 03-25-2009, 01:23 PM

The number on the back of my differential is R124 351 25 08 and when I do a search on that I come up with 4-Matic rear differentials!! I called my friendly MB parts guy and he looked up the ASD diff part number for a '92 300D 2.5T and said it should be 124 350 63 14. I Googled that # and didn't find anything. I don't know whether I have a Frankenstein rear-end made of 4-Matic parts (the ASD works) or what it is. I'm waiting for some sizes on 4-Matic Hubs to see if they're the same as mine or the same as the half shaft with the correct part number that doesn't fit. -RZ

zeiglerr · #15 03-25-2009, 03:18 PM

I found a PDF file online that has all of the key differential part numbers by chassis, model, and year. Great resource!
http://www.w124performance.com/docs/mb/other/differentials.pdf
The diff rear cover# on the 4-matic and sedan with ASD are the same (actually everything but the gear ratio and carrier, including the axle shafts are the same) so I'll have to do more digging. There's an axle flange# given, but I can't find a number on mine. I guess the differential will have to come out next.