Can I remove left side rear axle tube?

[Vince Canepa]

From what I can tell, the left side axle tube retains the bearings for the left side of the differential/ring gear without any adjustment feature (please correct me if I am wrong).  The right side of the differential has the adjustment nut.  My question is: can I safely remove the left side axle tube fron the differential casing and refit it later without disturbing the ring/pinion setup?

Vince Canepa
1967 250SL
113.043-10-001543
568H Signal Red
116 Caviar MB-Tex

[Benz Dr.]

You can, but why do you want to do this?  The outer race will be in the axel tube while the inner race will all the rollers is actually on the diff assembly.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org

[Vince Canepa]

Thanks for the response, Dan.  I hope I can explain well.  Where the axle tubes join the casting on the inboard ends (the fork casting for the central pivot on the right axle tube and the flange casting that holds the outer race on the left axle tube) there is what at first appears to be a weld joint (I'm not sure how these tubes were assembled).  On mine it is a very sloppy weld - what we call "making grapes" in the maritime industry.  In addition, it looks as though the welds are cracked.  I don't know if this is a valid concern or not.  Mine seemed to be weeping oil.  My next step is to plug the ends of the right axle tube and put a 5 PSI air pressure test on to see if the joint is indeed leaking.  I was thinking of putting a seal weld on the tubes.  I don't want the heat of the weld to affect the polyamide washers in the differential.  I am also concerned about the ground path for the welder.  In my business (large marine power plants) we always are careful about grounding so that weld current doesn't go accross a bearing surface.  It can arc and damage the bearing.  Anyway, since I have the axle assembly out I want to take care of anyting that may be a concern.

Vince Canepa
1967 250SL
113.043-10-001543
568H Signal Red
116 Caviar MB-Tex

[Benz Dr.]

The axel tubes are friction welded. They spin one piece at high speed and the parts just weld together. I believe drive shafts are done this way as it leaves both parts centered to each other.
The crack you see is normal and so is what appears to be a sloppy weld. Clean the vent tube on the axel housing so that there isn't any pressure build up inside the housings. I'd clean the welded area or grind it smooth and use JB weld to cover it if you're really worried that much.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org

[A Dalton]

The left tube can come off and the bearing outer race and required shim will just stay with the tube . the roller half will stay on the diff .
As long as you do not fool with the race and shim behind it, it should go back together with no changes.
While apart , you mat also want to check the long bolt that secures the slip joint/X assem. on the right side . They loosen and loctite is OK here.

[Benz Dr.]

You would have to pull the axel assembly first before you can even check the bolt that holds the slip joint in place. I'm inclinded NOT to use locktight on anything around these cars that might cause you grief when it comes time to remove the same part later on. There are a few places where it's OK because breaking what's coming apart wouldn't be a disaster ( you'd be replacing the whole part for new anyway )
Breaking this screw off inside the diff housing would be a real problem that didn't have to happen. There's a lock washer underneath the screw and if fastened properly it really shouldn't ever come undone. There's no end play or thrust on this part from what I can see. All end thrust is taken up by the slip coupling doing what it was designed to do.

Remember, we're trying to avoid problems. Not create ones that aren't even there.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org

[Vince Canepa]

Dan - On close examination I kind of figured out that the weld was something other than conventional "stick" welding.  What you describe explains it.  Thanks.  I became confused when I looked at a spare rear axle assembly Jim Villers has for his 190SL.  It appears to be conventionally welded.  I'm probably being paranoid, but I want to get everything while the car is apart.  Interestingly, the tab for the brake hose is attached in another unconventional way.  It appears that the tab was the "electrode" in an arc welding process, but the shock mountings appear to be conventionally arc welded (complete with the weld splatter).

Arthur - Thanks.  I pulled the U-Joint/Slip Joint so it will not get damaged while I clean and paint everything. The late Service Manual suggests applying a "locktite" type substance to the keyway (I assume they mean splines) and the bolt.  Is this something I really want to do? I can understand the bolt - but the keyway?

This is a car we show, so that adds a lot of work when perfoming any task.

Vince Canepa
1967 250SL
113.043-10-001543
568H Signal Red
116 Caviar MB-Tex

[A Dalton]

Vince,
 Yes , I have a Mod Attachment  from Benz on that somewhere here .. prob the same one you have in the later Service Manual.

 Anyway , lossening of the bolt was a common problem, so the loctite used is their specially formulated 243/oil resistent , mild lock w/removable strength. Not the High Strength old stuff, of course..
It is on their web site and is specially formulated for such an application with no fear of breakage at removal, if ever needed.    Correct tool/Correct compound.

 I just use a tiny bit and do not do the splines . As long as the bolt can't vibrate loose , should be fine. Might also consider a new lock washer. I also use the same on the rear pin nut of the trannies for the same reason, Another common loosening problem part.. there is a current thread here somewhere on that one too.
 * Added note*  on tranny nut torque ,while I am at it.
 Be aware that these tranny output flange nuts on the stick shift types have been known to have re-occuring loosening problems b/c the installer , even though he uses both a new lock plate and the  proper pin wrench [ instead of hammer/punch]  mis-takenly torques the nut to the auto tranny torque of 87ft/lb - 108Nm.  The Manual tranny spec on this part is actually higher than the auto , it is 108 ft/lb.-150Nm..
Just a heads-up on an often overlooked spec that can easily result in the potential of the same problem down the road..

[Vince Canepa]

Arthur - Thanks.  I am aware of the nut on the transmission outut flange (and I have seen the current thread).  Mine loosened up some time early in my ownership of the car.  I went through the transmission in '73 when the front seal leaked onto the clutch.  It needed nothing but seals.  I torqued the nut and it was still tight in '96 when I again went through the transmission again (seals again).  The problem I noticed way back when it came loose was that the speedo was slow in coming up to speed.  Bouncing, as discussed in ther other thread wasn't an issue for me.

Vince Canepa
1967 250SL
113.043-10-001543
568H Signal Red
116 Caviar MB-Tex

[Benz Dr.]

If there's special compound that might aid in keeping things in place while not causing undo difficulties during removal then I guess it might be OK if you're having a problem with something coming loose. I don't as a rule, use any locktight and use more antisieze and anything else.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org

[graphic66]

Most loctite can be loosened by some heat, and not a real lot. I have had scope mount screws red loctited on and would not come out. I didn't want to heat the firearm so I heated the allen wrench shaft and the heat went into the bolt and loosened it. Also if you use loctite it must be clean, and ideally primed with loctite primer. I just use starting fluid for the final clean. As the good doctor says I have not used any loctite on my car but loads of silver antisieze.

[Benz Dr.]

That's a good point and one I've thought about.
 How exactly, would you get heat to this screw inside of the slip coupling joint? Some of them are 14mm hex head and some are an allen screw I think. The allen screw could be a real bear to get out if you chewed the head up.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org