1984 300D Rear Axle Installation Trouble
 

Hi everyone, I'm brand new here!

The boot on the outboard side of my rear drivers-side axle broke and enough damage has been done that I'm replacing the axle.
I made short work of getting the old axle out this morning, however as I'm going to install the new axle I've run into some trouble...

It seems like the new axle (which I'm nearly positive is suppose to fit) seems like it is simply too long, even when fully compressed. Right now I've got the axle properly seated in the differential, however I still need at least 0.25" more clearance to get the outboard spline into the wheel carrier...

Here is the new axle I purchased for the job:
http://www.***************/search/product.aspx?sid=kkv0rxzkdig3zhzipwdixs45&partnumber=1233500410

Based on all the info I've found online it seems like the rear axles are essentially interchangeable, however the passenger side axle seems like it has a longer shaft between the boots than the old axle I took off the driver's side. Did I mistakenly buy an axle that's just too big? There's something I'm missing here...

Does anyone have some tips/tricks/insight/sage wisdom for me?

take it out of the diff, put the axle into the spindle first... then put it in the diff.

you might have gotten an SD/126 axle instead of the 123 axle, they are longer.
what is the measurement between the boot crimps?

Thanks vstech!
I've tried installing both ways. No dice, but I get much closer beginning with the differential end.
My old axle had ~5.75" between boot crimps, whereas the new one has ~8.5"
Sounds like I might have gotten the wrong part...
Any advice for where I can find the RIGHT one?
Thanks a lot!

I should note that the overall length of the old and new axles are exactly the same.
Here's a side-by-side of the two... Too bad I didn't notice the difference before I got the old one out!
https://flic.kr/p/owqKTV
(they are not 100% aligned in this photo)

That should fit, if it's the same overall length.

The way I found that made it easiest to insert the axle was to lift the differential up until it is just about touching the body of the car, then install the Diff end first, and then manipulate the axle's joints as needed to squeeze it past the heat shield and in to the spindle.

try pushing the joints completely together, then measure each length...

one could be compressed, and one could be stretched. that's the only way to measure overall length.

looking at the picture, I don't see 2.5 inches... the new axle appears to be compressed, while the old one appears to be stretched...

it is exceedingly difficult to get axles to fit, make sure both wheels are drooped, make sure the diff is jacked up as high as possible, and make sure the axle is fully seated and clipped into the diff, then it should fit into the spindle.

I've got the back end in the air, differential jacked up, new axle fully compressed and installed into the differential, and this is what I end up with...
https://flic.kr/p/owsmTU
I must be missing something here...
There still needs to be another 0.25" of clearance at least before the spindle will fit

The axles are definitely the same overall length, but the length of the shaft between boot crimps is a few inches longer on the new axle. Maybe that doesn't allow the joints enough room to maneuver? I'm thinking that maybe I've just purchased the wrong axle again. Do you guys have recommendations on ones that work well in 123s?

Thanks again for your advice, I really appreciate it!