Rear End Swap

[rb6667]

I have a 1971 280 SEL, 3.5 V-8, Auto Trans, that will be used for a parts car.  I understand that the rear end is the same as my 68 280 Sl Auto.   Any idea of what the ratio is in this rear end?   What size sockets, wrenches will be needed to get this thing out?

Thanks in advance.

RB6667

 

[Bernd]

The rear axle will have some numbers as well as the ratio stamped on the left side of the differential housing. In case of the SL it will look like this for example: 006928 4,08 SL........  The 4,08 is the ratio (and mine happens to be a '68 auto). The SE axle I believe has only numbers and no letters designation. Taking it out takes nothing special. i. e standard metric wrench set. Be carefull with the springs, of course. Good luck

[Naj ✝︎]

As Brend says, the ratio is stamped on the bottom rib on the left of the diff casing

Naj

[ctaylor738]

"Nothing special" is somewat of an understatement IMO.

For starters, you will need a 11mm line wrench for the brake lines.

If you are going to do this yourself with a floor jack, you will need some sort of a platform or frame to go on your jack.  The differential will pitch forward when it's released from the mount in the frame if you just have it sitting on your jack's saddle.  I used a 2' by 4' piece of plywood with large casters on the bottom, so I could move it around after it was out.

Assuming that you are going to replace the rear trailing arm bushings in the sedan rear end, you will need a 36mm socket to remove the large outside screws.  Then you will need a substantial vise or press to remove the old and install the new bushings.

When you lift the sedan unit into place, use a small level with a magnetic attach, and some shims to be sure that the big arm is level side-to-side and front-to-back.  Otherwise you will get it up into the mount and not be able to start the bolt.

You will also have to remove the cooling tube and plug the holes with 230SL drain plugs and copper o-rings.

Don't forget that you will need to keep your calipers and parking brake cables.

[Bernd]

Chuck, a basic mechanical understanding is obviously required to work on our cars, so I grant you that this is an undertaking that is not for a beginner. Having said that, with a decent mechanical brain it is really no big deal. I did mine in my garage with no help from anyone else and not even a lift....point is, it is a very doable task. Maybe I sounded like anyone with a screwdriver can do it, so my apologies, but the tools are not really that special. I welded myself a nice simple frame to support the axle when I released it, so tipping etc was no issue at all. No offense.

[waqas]

From what I understand, the SEL sedans have an air suspension and the rear axles are not inter-changeable with the SL. You'll need the rear axle from a non-air-suspension sedan or coupe/cab; designated by SE.

Replacing the axle is pretty straight-forward, but as with any major job, you need to prepare for all the details.

• The compensation spring will need a special technique to remove and install: either a custom spring compressor (which is what I did on my axle), or enough experience to not use one (what Ja17 and Dr Benz have done)
• The axle will need a good support structure to slide out from underneath (and vice-versa): you can get yourself a transmission jack and the factory tool for supporting both ends of the axle, or you can simply build a wooden contraption above your regular floor jack to do the same (this is what I did)
• You need to decide how many seals and mounts you want to replace. Complete all work on the donor axle before you remove yours.

I did this job several years ago, with the invaluable help of Joe Alexander and Arthur Dalton. The process is documented here: http://www.sl113.org/forums/index.php?topic=1642.0
Read through and familiarize yourself with the procedure.

[rb6667]

Very good information.  Looks like I have some reading to do.    A little more involved than I thought.   Glad I asked.

Thanks very much.  This will help alot.

RB6667

[al_lieffring]

The SEL 3.5 model that was offered in the USA was the 300SEL and that car did have air suspension, But the 280SEL 3.5 cars that were sold in all the other markets had spring suspension. If your SEL sedan had air suspension there would be no doubt about it, even when they were in the best condition the suspension would be down on the bump stops after 48hours not running.

[waltklatt]

The Robert Nitske book states that the 1970-72 280SEL 3.5 (108 E35) all had the 3.69 rear end ratio and less than 1,000 of them were made.  Pretty rare for that SEL body, but the short body 280SE 3.5 came in at over 11,000 units.
Hope this helps.
The rear end is a bit simple to do, not too hard.  If you have the mechanical know how of working on these cars and a generally well stocked tool selection, you can do it yourself in a weekend.

[rb6667]

Update.  I was given the wrong information about this car by my friend.  This appears to be a 1972, not a 71.  In addition, this is a 4.5 V8 not a 3.5.

Door jam plate reads as follows:

108.068-12-004902
Model: 280 SEL/1 4.5*
Date of MFG. 8/71

Additional information.  This car has the 4 bolt auto transmission pan.

Now that I have the right information, will the rear end out of this car fit a 1968 280SL?

Thanks again for all of your responses.

RB6667

[ja17]

Hello,

Yes, this is the  right diff. for the popular 3.27 conversion.  Check it for excessive "lash" (jack one wheel up and rotate wheel back and fourth).

[Larry & Norma]

Hi JA17, how much is excessive lash and how do you measure it?

[rb6667]

Gnuface, You beat me to it.  I have the same question.  Joe, please educate us all.

Thanks very much,

RB6667

[66andBlue]

You might want to watch the video where Joe explains the procedure:
http://video.google.com/videoplay?docid=6365474313884505435#

[rb6667]

Update!!!  I pulled the rear end out today working alone, even did it without a floor jack.  I put tires under the disc brake rotors, took the shock mounts loose, took off the trunk mount, and trailing arm mounts....and out or down it came.   Car was  already jacked up and supported on stands.    I left the trailing arms on until  last when I  was ready to drop it.  A litttle twisting and the springs came out easily since they we not under much compression at that point.

Thanks to 66 and Blue for the link to Joe's video.  I checked the ratio stamp and it is a 327.  Backlash feels great, hardly any at all.  It's tight.  Car had 127,000 miles on it.  Engine is toast!

Now the fun begins cleaning this thing up.

Thank You all for the responses.

RB6667



 

[Larry & Norma]

rb667, did you have to undo the sliding joint on the prop shaft as it says in the Haynes manual?
I think you need large wrenches for that.

[rb6667]

I took off the 4 bolts/nuts holding the driveshaft on the rear end side.  I think they were 13MM.  There was enough "Give" to release the driveshaft with just a simple pry with a screwdriver.  Did not take much at all to release it.

Today I put it up on jack stands in the garage, and will not start the dreaded cleaning.  Lots of Gunk on this rear....but it's a good one.

[rb6667]

Gnuface, I goofed.  The nut size is 17MM.  Remember this is a sedan driveshaft, so our Pagoda's may be different.   I have not removed the SL driveshaft yet.

The bolts have a large flat on them that prevents them from turning when the nut is removed.  There was enough room to put a large screwdriver through the back mount on the driveshaft ,to prevent it from turning while taking off the nuts.  Screwdriver was wedged up against the floor.

Hope this helps.

RB6667

[Larry & Norma]

Thanks for info. I have to replace a right side rear wheel bearing sometime, just trying to decide whether to
pull the whole axle and do the suspension rubbers etc at the same time. The 'Technical Manual' describes
left bearing replacement but not the right - I think the right one is more of a challenge so if anyone has any tips........

[DavidBrough]

Hi Larry,

I've done mine and there are two quite tricky bits involving the correct alignment of the new bearing in the axle casing and the fact that you have to raise both axle tubes to contact the body to ensure correct seating of the right hand half shaft. In the case of the former you just need to use two blocks of wood secured by bolts through the hub and I'll try and dig out some pictures for you as its quite difficult to describe but extremely effective. I think the BBB refers to a special MB tool for the job as it's virtually impossible without some sort of prior solid alignment but I found that the wood trick really works well. To complete the second bit you have to virtually remove the axle anyway so doing so is always an option at that point, however you will have to man handle it about and quite likely re set the alignment afterwards but that's not necessarily a bad thing.

I've also just remembered another thing, you should make a bearing puller as it makes like much easier, just obtain a standard universal two leg puller and purchase a length of steel about 25x2mm, I think you will need about 2 metres. You just cut two lengths and drill holes in the ends to extend the reach of the puller to cover the length of the half shaft and the bearing will pull straight off. I had heard that they can be easy to remove by just striking the end of the shaft on a block of wood but mine were going nowhere until I made the puller.

[Larry & Norma]

Hi David, Thanks for that really useful info.I am very interested in the pictures you may have
of the 'wood' method! I am hoping to leave it untill next September, MOT time as the bearing
got a mention this year but did pass anyway. I can feel movement by rocking the right wheel
so I guess it's only going to get worse.
Larry

[DavidBrough]

Hi Larry,

If you can feel movement in the bearing don't leave it too long as it may cause other damage.

Picture of the wooden chocs I used are attached. The idea is to use the back plate to hold the bearing square with the wood being forced onto the back plate by the bolts acting on the hub which then keeps everything held solidly in position so the bearing can't move when you hit the half shaft. You will also need some large washers to cover the holes in the hub and allow the bolts to apply pressure on the wood and back plate. You don't actually need to hit the half shaft very hard and one or two taps are all that's necessary to get the bearing started. I've done this a few times now and it always works first time.

[Larry & Norma]

Thanks for that David. I am sure it will all make sense when I take it apart. I may do it in the spring. It's too cold in my garage now.
Did you get the parts from sls? Do you use standard Lithium(LM) grease?Do you use a gasket sealant?
Larry

[DavidBrough]

I did use gasket sealer but I purchased some special bearing grease from halfords

[hkollan]

If your SEL sedan had air suspension there would be no doubt about it, even when they were in the best condition the suspension would be down on the bump stops after 48hours not running.

Al,

I am not sure how that myth got started, but I hear it from time to time.
A  W109 or W112 for that matter with a well sorted air suspension system, will not sink down for months. A well maintained  6.3 I owned would sit over the winter for more than 6 months without sinking down. Even when starting the car after winter-storage the suspension warning light would not go on.

Hans