rear end swap 4.08 to 3.27

[Cees Klumper]

To locate the trailing arm bushings I used a correctly sized pipe wrench that went through the large holes in the trailing arms and the rubber doughnuts, and onto the bolts on the chassis. It allowed me to manipulate the trailing arms (using the wrench as a kind of joystick) while a helper was moving the whole rear axle assembly back and forth a bit. Doing it this way made it fairly easy.

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[n/a]

I'm still working on the locating strut, darn it! I finally worked a c-clamp onto the axle-side strut bushings and compressed them enough to get the larger bolt threaded. I couldn't put much torque on the smaller bolt as about half the aluminum it threads into came out when I disassembled it. I may go ahead and install the trailing arms as the axle now hangs toward the rear, which means I have to lever it forward with a crowbar while trying to thread the strut rod back in. I'm getting pretty tired of heavy metal things falling on my face!

The hang up with the strut rod is getting it to thread in far enough to allow me to bolt the black metal plate back in place. I did avoid mangling the slotted end of the new rod by threading the 19mm on part way to keep the end from deforming. I'm about to back the rod back out after marking it to see how far it's penetrating the aluminum assembly.

John

quote:Originally posted by George Des

John

You and I are running somewhat in parallel here. I just today soldered up the same alignment tool to locate the rear axle. I had re-installed my axle some time ago but hadn't gotten around to doing any of the alignments. The car has not been mobile during this time since I had a host of other things I was woking on including the installtion of an A/C system. I did venture out of the driveway and around the block the other day to check some things out and I could tell that both rear and front alignment needs to be adjusted so now I'm on to that. I did notice from your post that you had lifted your rear axle in w/o the trailing arms attached. I had not considered that and had instead lifted my entire rear axle, trailing arms and all into place in one shot. Got to tell you, locating the bushings on the front end of the trailing arms where they mate with the body was a real pain especially since I did not have the centering cones that MB shows as a tool to aid in doing this. It occurs to me that you may have a much easier time doing this the way you are since you will be able to simply jack the rear of the trailng arm up into position on the rear axle and the mating "slot" will be able to hold it in position while you screw down those two big fittings on either side.


George Des

John Livingston
Newport News, VA
1968 280SL 4 speed manual

[n/a]

Yeah! The strut rod assembly is all back together. I had to sort of build it up from the axle side out, but with a bunch of pushing, pulling, and a modest amount of swearing, that component is done. Alignment still checks out nicely, too.

I'll probably tackle the trailing arms this evening, and then the brakes tomorrow.

Ever the optimist!

John

John Livingston
Newport News, VA
1968 280SL 4 speed manual

[Benz Dr.]

Why would you try and put it back together using known damaged parts? If the cross strut end has damaged threads get a new one.
I always put the whole axel together before I put it into the car - it becomes more difficult after th axel is mounted in the car. Earlier cars are hard enough to install but these ones have the added difficulty of the compensating spring forcing the axels. I usually place a 2x4 or piece of wood under the axel to help support the weight. I leave the cross strut in the car but not tight and use a floor jack under the diff to raise the axel into place. The centre pin should be fixed into place first and then the cross strut needs to be started. his best done while raising the axel into place. It's nearly impossible to do this by yourself - I have but not in a long time.

Daniel G Caron

[n/a]

Keep in mind this is the first one of these I've done!

Re the locating strut: I'll attach a picture of the part in question, showing which threads are stripped (tried three times, but got a "session timed out" each attempt. Will try it again this evening). I didn't get a new one as it had taken more than a month and nearly $200 (with shipping) to get the strut rod. The assembly had been untouched as long as  I've had the car, so it seems to have worked okay damaged for twenty-plus years. You have any idea what the aluminum part costs? It sure seems like sticking in a steel insert would be a better solution than buying a whole new unit. Is it just the SLs that have it made of aluminum? Seems a poor choice to shave a few ounces.

Re putting the axle back in as a unit: Now you tell me! I took the axle out and have been putting it back in pretty much as the manual states. I don’t think I had any suggestions to the contrary from the group. Yes, I’ve done it single-handed (although my son did help me lift it on to the jack initially). My one change to the procedure was pulling and reinstalling the compensating spring with the axle out of the car, which some folks haven’t been thrilled with

Right now I have the driver’s side brakes done, both disc and hand. I’m about to give the trailing arm on that side a go. It’ll probably be tomorrow before I get to the passenger side and get the drive shaft reconnected. We’re heading out of town Thursday, so I’m hoping to get it all bolted together for a short run before then. I got the shifter bushings finished a couple of weeks ago, so I may even be able to get it in gear!

Jumping ahead a bit: once I can get the front end in the air I hope to get the clutch hydraulics replaced and maybe do the tach cable.  Then I'll take the measurements necessary and send the speedo off to Palo Alto to get it recalibrated, saving the new speedo cable for when it gets back.

What a dreamer!

John

Yes, there were times, I’m sure you knew
When I bit off more than I could chew.
But through it all, when there was doubt,
I ate it up and spit it out.
I faced it all and I stood tall;
And did it their way.

quote:Originally posted by Benz Dr.

Why would you try and put it back together using known damaged parts? If the cross strut end has damaged threads get a new one.

I always put the whole axel together before I put it into the car - it becomes more difficult after th axel is mounted in the car. Earlier cars are hard enough to install but these ones have the added difficulty of the compensating spring forcing the axels. I usually place a 2x4 or piece of wood under the axel to help support the weight. I leave the cross strut in the car but not tight and use a floor jack under the diff to raise the axel into place. The centre pin should be fixed into place first and then the cross strut needs to be started. his best done while raising the axel into place. It's nearly impossible to do this by yourself - I have but not in a long time.

Daniel G Caron

John Livingston
Newport News, VA
1968 280SL 4 speed manual

[Benz Dr.]

Hey you didn't ask me.
 The only jobs I've never done on a 113 are rebuild injection pump, rebuild power steering pump and rebuild auto trans. I won't take the pinion shaft out of a rear axel - you loose the setting between the gears. They REALLY  whine if not set up closely.
I'd be inclined towards putting the compensating spring in before you get it up into place. Anything you can do now is less effort later.

The aluminum shackel is about 20 bucks list. All the cars from that time had them so a good used one should be readily available.


Daniel G Caron

[n/a]

$20! I didn't think any part on that car cost $20.

Let me try to upload the darned picture anyway, since I went to the trouble to take it.

Not much new to report. I spent  time tightening up some of the brake connections. I'm still hoping to get the remaining brakes and the trailing arms done tomorrow. I'm getting pumped enough that I'm having trouble sleeping. I should be out in the garage now, but I don't think the neighbors would like what I wear for PJs.

John

quote:Originally posted by Benz Dr.

Hey you didn't ask me.
 The only jobs I've never done on a 113 are rebuild injection pump, rebuild power steering pump and rebuild auto trans. I won't take the pinion shaft out of a rear axel - you loose the setting between the gears. They REALLY  whine if not set up closely.
I'd be inclined towards putting the compensating spring in before you get it up into place. Anything you can do now is less effort later.

The aluminum shackel is about 20 bucks list. All the cars from that time had them so a good used one should be readily available.


Daniel G Caron

Download Attachment: strutthreads2.jpg
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John Livingston
Newport News, VA
1968 280SL 4 speed manual

[n/a]

Driver's side is done! I had a heck of a time with the bushing to the front of the trailing arm popping out as I'd jack the arm home. I finally got it to stay put by liberally applying GB Cable Ease wire-pulling lubricant (I use that stuff all the time) and a small block of wood on a second jack to push the protruding bits of bushing home. I also used a scissors jack between the back of the differential and gas tank to help angle the axle forward and thus make it easier to line up the forward end of the trailing arm. I've - of course - got a picture of it all bolted up, but am having the usual timed-out uploading problems.

On to the passenger side. It's going to be a bit tougher as that side is fairly close to the garage wall. Brakes first, then trailing arm.

John

John Livingston
Newport News, VA
1968 280SL 4 speed manual

[n/a]

I've come to a grinding halt on the passenger side. I had left the old (cut by the seller) hand brake cable attached on that side to help remind me how it attached, etc. Well, I've removed the retaining clip but the cable housing is rusted solidly in place. I've tried hammering, vice (make that "vise") grips, penetrating oil, and heat, without any progress. The current plan is to hack saw off most of it on the differential side and then, maybe, drilling it out. Seems like I have sufficient access to do that, but I'm less than totally optimistic.

Any suggestions?

John

John Livingston
Newport News, VA
1968 280SL 4 speed manual

[graphic66]

If you can heat it with a Oxy/Acetylene torch to loosen it up.

[n/a]

I finished hack sawing and drilling the old handbrake housing. The biggest bit I had on hand was 7/16, which isn't big enough. I've got a half incher around somewhere, but my calipers measure the OD of the cable end that fits in the hole to be 16mm or .629 inch (if I'm reading that right). I fiddled a bit on the calculator and it seems the nearest fractional size would be maybe 41/64!  11/16ths works out to be .6875. I doubt I'm gonna find any of those at Lowes! Luckily the metal seems relatively soft and isn't too tough to drill.

Fun!

John

John Livingston
Newport News, VA
1968 280SL 4 speed manual

[n/a]

I tried the Harry Homeowner mapp gas routine, but I guess it wasn't hot enough.

The picture of the damage I've done with hack saw and drill bit is now attached for your amusement. Seems if I get it drilled out just a bit more, it should knock out.

John

quote:Originally posted by graphic66

If you can heat it with a Oxy/Acetylene torch to loosen it up.

Download Attachment: drilling_cable1b.jpg
50.01 KB

John Livingston
Newport News, VA
1968 280SL 4 speed manual

[n/a]

Lowes had a 5/8" bit (15.9mm) which worked great clearing out the remaining old hand brake cable housing end (after I bought a new drill to handle the 1/2" shank).

Back to putting the passenger-side brakes in, then maybe the trailing arm (it's my son's birthday, so we're off to Spiderman II and other diversions this evening).

John

John Livingston
Newport News, VA
1968 280SL 4 speed manual

[n/a]

We're about to hit the highway for the 4th of July weekend. Alas, it won't be in the SL.

I did finish getting the passenger-side brakes back in place. I was feeling confident enough that I hooked up the battery charger and put the pressure bleeder on the master cylinder. I got most of the air out of the rear passenger-side caliper before noticing that fluid was leaking rather rapidly out from under the brake reservoir's front cap. Time to order new O rings or gaskets.

The passenger-side trailing arm is bolted to the axle, but I ran out of time before I could get it bolted to the underside of the car. It seems to be lining up pretty decently, at any rate.

So, we'll be returning Monday and I'm hoping to at least get the trailing arm done and maybe the drive shaft reconnected. I think I have enough brake pedal to get a brief test ride in once those are done.

John

John Livingston
Newport News, VA
1968 280SL 4 speed manual

[n/a]

It works! Just back from moving it all of about 30 feet. The poor thing fired right up, after sitting for five months. I need to reattach the soon-to-be-replaced resonator as it's just hanging from the head pipe. I pulled the car out of the garage so I could get better access to the passenger side.

So far, no weird clunks, squeaks, etc.

Spent yesterday changing the differential fluid, bleeding the brakes the conventional way, attaching the passenger-side trailing arm, the hand brake cables (the lever isn't ratcheting and thus won't stay up - I'll have to take that apart and get it unfrozen)., and the driveshaft bolts. Today I just needed to do the rocking back and forth to adjust the drive shaft, tighten those center bearing bolts and the slip nut, and air up one of the tires.

I'll get the exhaust anchored and then will take it for a short spin. Then I'll jack up the front end, change the engine and transmission oil, install the new clutch master and slave cylinders, and then see about it getting it inspected. At some point I'll give it a wash, too, as it sure is dusty.

I'm working up a few web pages summarizing the job. I've got the tool list pretty much done and will post the link here shortly.

Next I need to finish the heater levers, get the radio hooked up, and figure out where to drill the hole in the fender for the antenna. Then, let's see, it's the convertible top install, new carpeting...

Thanks to all for the great help and encouragement (I hope I'm not being premature!). More soon.

John

Download Attachment: fertig2.jpg
61.21 KB

John Livingston
Newport News, VA
1968 280SL 4 speed manual

[Ben]

seems like your nearly there John, I sure hope it was worth the effort, I reckon it WILL be and we're all waiting with baited breath to see what the RPM's are on the Freeway !

Regards,
Ben in Ireland.
'64 230SL 4sp.
'03 CLK Kompressor

[n/a]

Right now the front end is up on ramps while I'm draining the crankcase. I was interested to see how much clutch slipping I had to do to get it up on the ramps. Seemed pretty close to normal - no clouds of clutch smoke so far!

John

quote:Originally posted by Ben

seems like your nearly there John, I sure hope it was worth the effort, I reckon it WILL be and we're all waiting with baited breath to see what the RPM's are on the Freeway !

Regards,
Ben in Ireland.
'64 230SL 4sp.
'03 CLK Kompressor

John Livingston
Newport News, VA
1968 280SL 4 speed manual

[n/a]

Just back from the first, brief drive . No highway miles yet as the access panels are still off the transmission tunnel, dash parts are strewn all over the interior,  and it has less than half the exhaust system in place. Still, I like it! Starting in first gear seems much more normal. You need to work the clutch a tad bit more than before, but then previously I could start it from idle without giving it gas if it was on a level surface. There's none of the sense that you're getting a truck underway. First and second seem much more flexible for normal motoring. I'm going to give it a bath, organize the interior parts, and then see if I can get it to my local mechanic for a state inspection and exhaust install. Once that's done, I'll give the highway a try.

Love those new shifter bushings!

John

John Livingston
Newport News, VA
1968 280SL 4 speed manual

[Cees Klumper]

Just a note John: the highway RPM's will appear to be exactly the same as before the swap! I noticed this when I changed the rear end on my car from 4.08 to 3.69 two years ago. The reason is that the speedometer is linked directly to the drivetrain. Before the swap, your tach probably showed e.g. 4,200 RPM's at 75 MPH; it will now show the exact same value with the 3.27 rear end. Only, you will be actually going 93 MPH. The speedometer will have to be modified to the different rear end ratio. Before the swap on my car, the speedo read 5% too fast (calibrated on an Amsterdam-Stuttgart trip). Now, after the swap, it reads 5% too low (calibrated yesterday on an Amsterdam-The Hague trip. And indeed the change from 4.08 to 3.69 is about 10%).

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[n/a]

Thanks, Cees. I'm afraid I've been around long enough that I anticipated the fixed speed/rpm relationship. (A cop explained it to me nearly 40 years ago when I put oversized tires on the back of my VW beetle!) I figured I'd hit a steady, nearly-legal highway speed, note the rpm, and then calculate my speed by timing the rate at which the mile posts are passing by.

I hope to order some new tires fairly soon since the ones on the car now are more than 20 years old! Once those are mounted, I'll see about getting the speedo professionally recalibrated.

I'm still working on the tool list to post to the web (and eventually some pages and pictures describing the process). I recall seeing some home-made drive shaft wrenches on eBay that I thought were made by a Pagoda group member. Does anyone recall who that was? I'd like to include them on my parts list if some are still available.

John

quote:Originally posted by cees klumper

Just a note John: the highway RPM's will appear to be exactly the same as before the swap! I noticed this when I changed the rear end on my car from 4.08 to 3.69 two years ago. The reason is that the speedometer is linked directly to the drivetrain. Before the swap, your tach probably showed e.g. 4,200 RPM's at 75 MPH; it will now show the exact same value with the 3.27 rear end. Only, you will be actually going 93 MPH. The speedometer will have to be modified to the different rear end ratio. Before the swap on my car, the speedo read 5% too fast (calibrated on an Amsterdam-Stuttgart trip). Now, after the swap, it reads 5% too low (calibrated yesterday on an Amsterdam-The Hague trip. And indeed the change from 4.08 to 3.69 is about 10%).

Cees Klumper in Amsterdam
'69 white 280 SL automatic

John Livingston
Newport News, VA
1968 280SL 4 speed manual

[n/a]

A brief update:

I dropped the car off yesterday morning for state inspection and exhaust install. The mechanic is having a tough time with the connecting pipes from the resonator to the muffler not lining up right (that's what I get for buying Swedish parts?). He claims he'll be able to correct it with enough heat. I just hope all the undercoating won't be burned off the car in the process.

It flunked state inspection for two reasons:
1. it needs tie rod ends on the driver's side (I think they'd replaced the passenger side ones a couple of years back). I've got those ordered.
2. the mechanic can't figure out how to get the windshield defrost to work (which apparently is a state requirement) with no heater levers in place! I guess I'll stop by there Monday morning and shift the heater cables to the proper position. I sure hope he hasn't been monkeying around in the dash.

I did get to enjoy the new ratio a bit more on the drive to the shop (which is within walking distance, so it wasn't much). I used to have to really concentrate to start the car off smoothly, and I've been driving stick shifts for a lot of years. Now you just motor off, without any extra effort on your part. Sweet!

I'm hoping to get the heap back by Tuesday, at which point I'll do the highway RPM check and let you know.

John



John Livingston
Newport News, VA
1968 280SL 4 speed manual

[Benz Dr.]

I never replace tie rod ends and change the whole assembly instead. Complete assy is about 40 bucks.

 The new parts make it easy to adjust the front end. If I have it at home I remove the old unit in one piece and then I place it on top of a peiece of wood. I pund a nail in the wood and then another one at the other end and then bend the nails until they just touch the tie rod ends.
Adjust the new assembly so that it just slides through the nails and the car will drive straight enough you may not need any alignment work or just a minor adjustment.

Daniel G Caron

[n/a]

quote:Originally posted by Benz Dr.

"I never replace tie rod ends and change the whole assembly instead. Complete assy is about 40 bucks."

I hadn't thought about that. What a great idea. I found a pair of complete tie rods on ebay for about $60 with shipping.

 "The new parts make it easy to adjust the front end. If I have it at home I remove the old unit in one piece and then I place it on top of a peiece of wood. I pund a nail in the wood and then another one at the other end and then bend the nails until they just touch the tie rod ends.
Adjust the new assembly so that it just slides through the nails and the car will drive straight enough you may not need any alignment work or just a minor adjustment."

This certainly sounds like a good plan. But it does beg the question, what do you do when you're not at home?

Thanks!

John

Daniel G Caron

John Livingston
Newport News, VA
1968 280SL 4 speed manual

[TheEngineer]

I have changed the rear axle on my '69 280SL from a 4.08 to a 3.27 and have now driven it a few thousand miles. I have an automatic. At 62.5 MPH (100 KM/h) my engine turns 3000 rpm instead of 3800. The speedometer now reads slow: 40MPH indicated is actually 50. I have printed stickers and attached them to the speedo to remind me to multiply the indicated speed - and the odometer - by 1.25. I consider the swap a full success and sold the old rear axle for $63. Naturally, acceleration suffers a little, but if I want to burn rubber, I kick down and start in 1st gear. I don't do that very often. The car has become very pleasant to drive on the freeway and "Operation Linke Spur" is in full swing.

1969 280SL,Signal Red, A/T, P/S, A/C, Both tops.    Ret. engr.

[n/a]

Good to hear your swap has been such a success. I expect my RPM change to work out to be the same 20 percent drop you got, since 80 percent of 4.08 is 3.264.

The guy I bought the 3.27 from claimed he wouldn't drive a W113 without this change, particularly if it were a manual gearbox. I think there may be some engine tuning that plays a part here. Perhaps if the engine is really singing the way it did when it was fresh from the factory, those deep gears wouldn't be such a burden. Still, for the sort of driving I do, I think this'll be the way to go and that the car will see a lot more use as a result.

John

quote:Originally posted by theengineer

I have changed the rear axle on my '69 280SL from a 4.08 to a 3.27 and have now driven it a few thousand miles. I have an automatic. At 62.5 MPH (100 KM/h) my engine turns 3000 rpm instead of 3800. The speedometer now reads slow: 40MPH indicated is actually 50. I have printed stickers and attached them to the speedo to remind me to multiply the indicated speed - and the odometer - by 1.25. I consider the swap a full success and sold the old rear axle for $63. Naturally, acceleration suffers a little, but if I want to burn rubber, I kick down and start in 1st gear. I don't do that very often. The car has become very pleasant to drive on the freeway and "Operation Linke Spur" is in full swing.

1969 280SL,Signal Red, A/T, P/S, A/C, Both tops.    Ret. engr.

John Livingston
Newport News, VA
1968 280SL 4 speed manual