E46 M3 Diff/axle questions

I'm normally able to reasonably quickly make decisions, but I'm struggling with this one.  2003 M3 convertible with 135K miles.  Got a clunk noise in the rear when cornering.  Right side diff output flange moved a lot radially, so I figured something in the diff was shot.  Pulled the diff and took it apart, and everything I can see looks great.  Online research indicates the sloppy output flange is common and seems to be fixed by replacing bearings.  It seems the reason to even bother is when that seal leaks, but it doesn't damage anything in the diff.

While the diff is out, the inner CV joint on the right axle is dripping what seems to be diff fluid.  More careful inspection of that CV shows significant play in the joint.  So now my operating assumption is that the flange seal was leaking into the CV joint (not sure how, there haven't been any drips on the floor, and while there is some grime on the underside of the car in that area, it's not crazy), and the oil wiped out the grease and caused the CV to wear quickly creating the clunking noise.

The car is just a street cruiser, so I'm thinking of doing bearings and seals in the diff and a new CV joint or axle shaft.  This is where I'm struggling.  Rebuilt diff from diffsonline / Bimmerworld is $1650 (plus $1500 core!).  Complete bearing and seal rebuild kits, including pinion bearings and seals which I'm not sure I want to take apart, are $350 for no-name ebay to 600-700 for BMW or diff specialists.  Rock auto has all the bearings (Timken) and seals individually for sub-$100 for the diff carrier bearings and seals.  Anyone see an obvious reason to go one direction or another?

The CV and axle shaft is a similar dilemma.  Rockauto sells Trackmotive axles for $90.  Seems really cheap.  Anyone with experience with them?  FCP Euro lists BMW axles for $700 each (backordered), and the BMW racing community seems to sell pairs of upgraded performance axles for $1200.  I was hoping for name brand CV joints on a mid-grade axle, but I haven't found that.  I'm leaning towards the cheap Rockauto path since it's hopefully not crazy to swap if it doesn't last long.  Thoughts?

I was afraid that was too much detail for anyone to read.

TL:DR

Anyone have any experience with Trackmotive CV axle shafts?  Any midgrade options for a BMW?

Anyone have recommendations for BMW differential service parts like bearings and seals?

No way to get diff fluid into the inner joint. 

I am no help as mine's are at 143k miles amd still OK. I did have to reseal the whole diff and get a new cover as the bushings were gone. 

Does FCP euro offer anything else? I would try and go with something cheap from them as it has lifetime warranty

Looks like there is only one side axle avail from BMW. Not sure what the difference is side to side. 

The difference side to side on the axles is different engagement length of the splines to the differential.  Are the boot kits available from any source? It may be worth it to pull the offending axle apart & see if something is out of place & nothing is damaged.  Axles are not a common failure so a low mileage used one maybe a good option as well

In reply to Caperix :

The inner stubs are not part of the axle. 

Actually, not 100% sure but I even think the stubs or whatever you call them are interchangeable side to side. 

I haven't looked at disassembling the axle yet.  CV joints are available separately, so maybe I should try that.  Anyone know how hard it is to get the CV off?  Just a circlip and tapping with a hammer?

Oil is still dripping from that CV joint.  I also don't see how that could get from the differential to the inside of the CV.  Strange.

Yep, remove the cap and there is a cir-clip there and the you fight it off. 

Its impossible to go from diff to axle, most likely the gear oil there got cooked off and lost its thickness? 

Is it reasonable to attempt to remove the CV while the axle is still in the car?  I've heard it can be really hard to get the axle out of the wheel hub.

In reply to pkingham (Forum Supporter) :

I think it could be done. Just have to be mindful of the outer joint and boot. 

If it was me, these are the steps I would take:
- Remove the 6 allen holding the inner to the diff and lower that side.
- Loosen the axle nut leaving the nut flush with the axle. Giving it a good whack with a good 5# or whatever sledge.  If it moves, take it out and work on it outside the car. If it doesnt attempt in car.

They can be a bear to remove, mine's came out easy. Probably because Florida and no rust.

I personally would try to remove the axle but be cautious not to over stress the wheel bearing. Worst case it is really 30 minutes of work to drop the entire hub assembly and then you could do a R&R on the wheel bearing and axle. 3 bolts on the trailing arm, one lower shock mount, one sway bar, remove brake line, unbolt rlca. 

If you have a battery powered impact shouldn't take very long at all. I would just do both sides with new bearings and rlca joints as well as trailing arm bushings considering they aren't expensive and have quite a few miles on them.

BMW suspensions really are a while you are in there whore.

^ This is good advise. 

I spaced on that, the e46 does use separate stub axles from the rear axles.  If you are lucky the axle will push out of the hub without much force, road salt exposure will probably be the deciding factor.  If the hub nut is not roting away soak it in some pb blaster & it should come out with minimal force.

Well, with the axle still in the car, I popped off the cover on the inner CV joint, removed the circlip, and discovered that the rotational play was all in the spline.  At that point, only the boot prevented the joint from just coming right off.  I can't see any obvious wear in either the shaft spline or the CV joint spline, so I'm now thinking replacing just the CV isn't the right answer.  El cheapo shaft assembly is where I think I'm headed now.

I know the old one is junk, but save it just in case. You might be able to use as core if the cheapo one fails. 

Well, el cheapo axle shaft (actually outer CV) failed yesterday, only 2 years and 4k miles later.  And I'm back in the same situation I was in before.  Ugh.  It seems that there are cheap options, more expensive options that appear to be heavily marked up cheap options, and custom pieces developed for race and/or high power applications.  I guess I'll try a different cheap option.

I would buy junkyard oem axles and re-boot them before I'd put Chinese axles in a European car.

Streetwiseguy said:

I would buy junkyard oem axles and re-boot them before I'd put Chinese axles in a European car.

Agreed. Check out the part out for sale section of some of the forums and buy one from a lowish mileage wrecked car.

This guy parts out M3s

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