Installing Rear Axle

[JimVillers]

I bought a 3.75:1 rear axle to install in my 230SL.  After replacing the solid boot and greasing the axle bearings, I am thinking about at how to install it in my garage with "normal" tools.  I have swapped 190SL axles and springs with a floor jack and lowering the axle to take the tension off of the springs.

My problem is the camber spring.  I don't want to install the spring before installing the axle and can support both sides.  Likewise, I don't want to drop the old axle until the camber spring has been removed.

I have been testing an ad hoc  threaded rod spring compressor but that spring really needs to be compressed a lot before the perch can be removed.

What are the tools and procedures that been successful?

[waqas]

Jim,

When I replaced my rear axle a few years ago, I made my own internal spring compressor for the compensating spring. I detailed my compressor in the following thread entitled "Replacing my 230sl differential..." located here:

http://sl113.org/forums/index.php?topic=1642

I also have pictures there which show how I supported the entire axle with wooden contraption attached to my regular floor jack. Just ask if you want more details!

[JimVillers]

Wagas .... I read the thread but I still am not sure how to compress the compensation spring.  Did you put a threaded rod through the differential perch?  Do you have a picture of the compression tool that you used?  If I can get the compensation spring compressed, the rest will be "just work".  Did you need to remove the fuel tank?

[waqas]

quote:Originally posted by JimVillers

Wagas .... I read the thread but I still am not sure how to compress the compensation spring.  Did you put a threaded rod through the differential perch?

Yes, the threaded rod (together with the two metal plates) is the spring compressor. The nuts are used to hold the plates from the outside. The plate on the right holds the spring (some number of coil turns from the end), and the plate on the left holds the differential spring perch.

quote:Do you have a picture of the compression tool that you used?

Here is the picture from the previous thread showing the complete setup (albeit loose):
Download Attachment: pagoda-comp-spring-rear.jpg
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quote:Did you need to remove the fuel tank?

No I didn't, but this made it really tight in there. If you don't remove the tank, I would strongly suggest raising the car as high as safely possible on your jack-stands.

Here is the entire procedure quoted from the previous thread:

quote:Originally posted by waqas

I used a 15" long 0.5" diameter threaded bolt (Home Depot, about $3/ft), some washers and nuts, and a couple of home-made metal plates.

Download Attachment: pagoda-comp-spring-parts.jpg
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The plate holding the spring (on the right in the photograph) is about 5"x2"x0.25", with a 0.5" hole drilled through the centre. The plate on the left is about 3.5"x2"x0.25".

(0) As a prerequisite, relieve as much tension from the compensating spring as possible. An old post by Joe Alexander mentioned removing the shock absorbers, and slowly lowering the axles, always keeping them fully supported. Also, slightly loosen the two spring mount bolts on the right (axle) side.
(1) slide the threaded bolt through the spring from the differential side of the mount (left to right).
(2) slide the 5" long plate through the spring, a few coil turns from the end, and slide the bolt through the plate.
(3) carefully slide a nut through the spring, on the right side of the plate, and screw-in the bolt until it almost hits the mount on the right. This was the painful part, but a thin pair of clamping pliers holding the nut really helped.
(4) place the smaller plate on the left side, along with any washers, and tighten with a nut. Be sure to grease the bolt threads on this (the left) side before tightening, as this is where the spring will be decompressed from.

Download Attachment: pagoda-comp-spring-side.jpg
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(5) tighten the left nut until you hear the spring compress ever so slightly. now tighten a little more.
(6) carefully remove the two bolts (inner one first) holding the right mount, and remove the mount. The spring will now be compressed against the differential side mount.
(7) slowly loosen the left nut (remember the grease?) until the spring has completely decompressed (this is where the 15" bolt length comes in handy), and remove the spring.

Download Attachment: pagoda-comp-spring-rear.jpg
50.46 KB

Hope this helps!

[DavidBrough]

Hi Jim,

I swapped my axle recently and made the compressor described by Waqas which worked very well. You are better removing the compensation spring beforehand but don’t actually need to as it will come out with it in place however you are best to at least take some pressure off it to be sure that undue strain is not placed on the right axle tube. I didn’t have to raise my car that high and was able to remove the axle from the back out under the fuel tank, the issue is to get enough clearance for the diff hanger and you need to have the car a lot higher to remove it that way with the spring in place. When I put the new axle in I decided it would be easier to put the compensating spring in first and leave the spring compressor on as it is a bit of a pain winding it in when on the car. If you do this then you can relieve pressure on the spring by jacking the axle tube and the compressor is then much easier to undo in place. As a result I had to slide the axle in from the right hand wheel arch as it wouldn’t fit under the fuel tank but it wasn’t too tricky. I also made a wooden bracket to lock the axle in place when the spring was removed which made it a lot easier to move around.

Good luck

David Brough 1969 280Sl Auto with A/C & 3.46 Axle

[JimVillers]

Wagas .... Thanks.  I'm off to give the removal a try.

[JimVillers]

Well the rear end has been successfully been swapped.  This was one of the worst jobs I have done in many years.  The compensation spring is a b*#ch to install.  I must have spent three hours trying to compress the spring with various compressors and strategies.  Putting a piece or old iner tube rubber under the compressor plate to keep it from slipping was one of the keys  .  Another key was to using a ratchet strap to hold the spring in the vacancy of the perch.  I found that I could not lift the center member because the swing axle would swing and the spring would come off of its perch, so I just lifted it by the ends and used the spring to lift the center.

Enough complaining; the axle is in, the springs and trailing arms are attached, the center support is bolted in place and the U-joint is attached.  Tomorrow, I'll tighten everything, install the brakes and exhaust.  

[waqas]

Amazing... there was exactly 10 hrs and 10 mins between your last two posts... you must have a couple helper clones!  

[JimVillers]

Just to complete the thread.  Everything is finished; (I also dislike re-installing the exhaust pipe.  Getting both pipes and flanges aligned under, alone is a chore).

Anyway, I love the new ratio.  It was worth the work as the 3.75:1 differential changed my shift points and cruising RPM almost 10%.  I feel like I am using more of the available torque verses just reving the engine.  The 3.27:1 would probably have been better but this is enough of an improvement that I don't feel that I "need" the 3.27:1.

[wwheeler]

Is it possible to exchange gears and still retain your original rear axle? Mine is a 4.08 and how it does scream down the highway! A 3.75 sounds much better.

[JimVillers]

Wallace .... Yes, you can swap gears in your housing.  New 3.75:1 ring and pinions sets are available from Mercedes.  (I swapped ring and pinions in my 190SL because I couldn't locate a 180D 3:70 differential).  Swapping gears takes some skill and special tools to get the gears set up with the correct mesh pattern and specified bearing preload.  It is easier to just find a used axle.  The one I found came complete with rear brake drums (nice to have these expensive spares).