Help! New Axle installation in '85 300TD - PeachParts Mercedes-Benz Forum

FeldmanCello · #1 10-07-2016, 05:44 PM

First post here! I've enjoyed reading these blogs for previous projects. I am in the process of replacing my rear CV axles in my '85 300TD, w123 chassis. I got the old ones out, put the new ones in differential side first, c clips are installed, and now I can't seem to get enough clearance to get the outer spline to the hub. As you can see from the photos, I need another 1/8"-1/4" of horizontal space to get the axle behind the hub. (for some reason the photos uploaded upside down...?)

Things I have checked/done so far:
- I know the differential splines are in completely since I got the C clips installed.
- I checked the replacement axles and they are the same length as the originals (USA remanufactured)
- the axle joint is completely compressed to make the length as short as possible.
- I saw on other blogs that you can lower the hub further by releasing the shock bolts behind the back seat. I did this, which lowered the wheel an extra inch or so. The differential is jacked up to the subfloor, but the control arm/hub rises as well when I jack up the differential. I'm not sure how or where the differential/shaft is connected to the control arm.

Any other thoughts on how to get extra horizontal space would be greatly appreciated. I'm afraid if I use force to move the axle into place I will damage either the splines of the axle or the bearings.

Steve_in_NV · #2 10-07-2016, 06:52 PM

I think you need to disconnect the diff and lower it a bit. There are two bolts on the top securing it. And you are correct the shocks need to be disconnected. For some reason I think I inserted into wheel hub first then the differential, it's been awhile. Don't forget to tighten (torque) axle shaft to wheel hub bolts. 8mm bolt 7 ft. lbs, 12mm bolt 21 ft. lbs.

charmalu · #3 10-07-2016, 07:26 PM

It`s been quite a while for me also replacing an axle. Probably close to 6 yrs.
They are a tight fit. Don`t remember which end I replaced first, but I replaced the "C" Clip last.
I also had the Differential unbolted from the body on a floor jack to raise or lower. There is the 4 13mm bolts that holds the Diff Mount to the body, these are what I remove.

If you remove the 2 in the center of the mount, they are 22mm as I remember.

Here is a DIY link to replacing the Differential by DELIVERYVALVE several yrs ago. Shows how he R&R`d the axles with pictures.

PeachPartsWiki: Replacing the Differential

Is yours a one piece or two piece axle?

If you have the two piece, (Annular style) you can remove the 6 bolts, place the Stub in the Diff. and put the Splines in the Hub, then rebolt the two halves together.

A few more links

http://www.peachparts.com/shopforum/diesel-discussion/220000-w123-how-replacing-rear-axles.html

here is the Wiki from that thread.

PeachPartsWiki: Replacing the Rear Axles

Here is a Google search I did with more info

https://www.google.com/search?q=site+peachparts,+replacing+w123/w126+axles&biw=942&bih=449&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiOgbba7cnPAhUSzWMKHYG2AM4Q_AUIBygC&dpr=1.45
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Ceristimo · #4 10-07-2016, 08:07 PM

I did this on a W123 sedan beginning of this year and indeed had the diff unbolted, and lowered it a bit supported by a jack.
That gave ample space to get the new axles in. Had no problems that way.

C clip was the last thing to put on.

FeldmanCello · #5 10-07-2016, 09:38 PM

That is a good idea- I will try removing the bolts around the new annular axle so I can get both spline ends in first, then put the axle together. Anyone know what the torque spec is for the annular axle bolts?

I did not mention this specifically if my
original post, but my diff is already unbolted and freely moving on a floor jack. I've tried at every height so far.

A side question: does leaving the diff "hanging" at its lowest position cause a lot of strain on the driveshaft? My floor jack seems to creep down overnight.

You all are great. Thanks!

vstech · #6 10-07-2016, 10:59 PM

the driveshaft is connected front, middle and rear with rubber... so, yeah, letting it hang can cause failure. you may seriously wish to TOTALLY inspect all the parts. look over the flex discs at each end, and check the boot/mount in the center bearing. DON"T TAKE THEM APART, unless you wanna replace them. the bolts are one time use only... so, if you take them apart, you need to replace the bolts.

as for clearance, be sure the vehicle is supported by the frame, NOT the subframe... you need full movement of trailing arms, and the subframe to get the clearance. lifting the trailing arm, while dropping the diff gives you plenty of room. but if you have one wheel on the ground, and one in the air... the swaybar limits movement.

charmalu · #7 10-08-2016, 01:51 AM

Try wedging in a 4 x 4, 4 x 6 block of wood, so when the jack bleeds down it will bite into the wood.

I have a parts car out side sitting on a FJ with wood wedged in to hold it, and my 85
in the shop sitting on a FJ because of a leaky tire.

Holds them good. 85 has been like that for 2 years.

for the bolts holding the 1/2`s together. Clean the threads off good and apply Lock-Tite before tightening them down. Don`t know the torque setting.

On mine, just made them gootentite.

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FeldmanCello · #8 10-09-2016, 09:00 AM

Success! Got the axles in by disassembling the halves, then reassembling after insertion. Driver side is all set. On the passenger side there was a slight bit of play with the C clip, and therefore the axle itself. After testing the c clip on the old axles and measuring the radius of the groove, I determined that the problem was the actual width of the c clip groove on the new axle, which was slightly wider than the one on the OEM axle I removed. Because it was only the case with one axle, it leads me to think it was a manufacturing defect, and I ordered a replacement.

Questions moving forward:
1) Since the differential was hanging under its own weight overnight, I am planning to inspect the flex disks and the mount/bearing on the driveshaft. Are there any other points to check for damage?

2) How difficult is it to replace the oil seals in the differential? I believe my boots were leaking on the old axles since there was oil buildup on the inner and outer portions of the axle. But I could also have a seal leak. Is there a way to tell if there is a seal leak without cleaning the diff and waiting for new buildup over time?

Frank Reiner · #9 10-09-2016, 10:57 AM

Quote:

Originally Posted by FeldmanCello

Success! Got the axles in by disassembling the halves, then reassembling after insertion. Driver side is all set. On the passenger side there was a slight bit of play with the C clip, and therefore the axle itself. After testing the c clip on the old axles and measuring the radius of the groove, I determined that the problem was the actual width of the c clip groove on the new axle, which was slightly wider than the one on the OEM axle I removed. Because it was only the case with one axle, it leads me to think it was a manufacturing defect, and I ordered a replacement.

Questions moving forward:
1) Since the differential was hanging under its own weight overnight, I am planning to inspect the flex disks and the mount/bearing on the driveshaft. Are there any other points to check for damage?

2) How difficult is it to replace the oil seals in the differential? I believe my boots were leaking on the old axles since there was oil buildup on the inner and outer portions of the axle. But I could also have a seal leak. Is there a way to tell if there is a seal leak without cleaning the diff and waiting for new buildup over time?

The end play of the inboard stub axle(s) is set with selective washers, they are the ones that are found between the shoulder of the axle and the end of the diff carrier (in the side bearing). You should be able to rotate the c-clip but also have zero end float of the stub axle.

vstech · #10 10-09-2016, 11:03 AM

Look on your old axles... if any shims stayed there, they need to stay with the diff. Missing shims will lead to play on the axles.

Seals around the axles need to be changed with the new axles. Easy peasy.

If your yoke seal is leaking... it is a major undertaking to replace.

dennislarock · #11 10-09-2016, 04:58 PM

I did not read the thread but if they are Homokinetic... Ditto on the Shims... they also must go onto the side they came off of. The shims match the differential i.e., 3.07, 2.88 etc. There should be *no* play whatsoever.

FeldmanCello · #12 10-09-2016, 05:29 PM

Would these shims be still in the diff, or would they have come out with the old axle?

Frank Reiner · #13 10-09-2016, 05:36 PM

Quote:

Originally Posted by vstech

Look on your old axles... if any shims stayed there, they need to stay with the diff. Missing shims will lead to play on the axles.

Seals around the axles need to be changed with the new axles. Easy peasy.

If your yoke seal is leaking... it is a major undertaking to replace.

Quote:

Originally Posted by dennislarock

I did not read the thread but if they are Homokinetic... Ditto on the Shims... they also must go onto the side they came off of. The shims match the differential i.e., 3.07, 2.88 etc. There should be *no* play whatsoever.

The myth, that is alternately either an "urban myth" or "a backwoods folk tale", that says that the shims are specific to any given differential is just so much nonsense. The thickness of the shim is selected to accommodate the combined manufacturing tolerances of both parts, the diff case and the stub axle together. Further, the shims have absolutely nothing to do with gear ratio.

dennislarock · #14 10-09-2016, 07:01 PM

Sometimes they stick to the differential but *usually* they stick to the axle. I have no idea whether or not the shims apply to annular axles. I put a set of rebuilt homokinetics on my wagon ('85 2.88 rear end) something like nine years ago and remember that I got the left and right shims mixed up initially and had to swap them for a perfect fit... one side went in to easy the other I could not get in... so I swapped them... and, perfection.

dennislarock · #15 10-09-2016, 07:02 PM

I beg to differ... check the shop manual. It's not the gear ratio... its the housing... i.e., tolerances. Your shims *match your differential*... be it 3.07, 2.88 etc.
I should add that I have a dozen or so shims that I got from a re-builder and in that batch... five (5) of the shims are of different thickness. I have no Idea how many different thicknesses there are.