Rear Axle 3.69 Conversion

[nirmal]

Hi Guys

I have a 1969 Automatic and am looking to convert to a 3.69 Rear Axle.

Any ideas where I can source one and what is the process.

Any help will be appreciated.

Nirmal
1969 280 SL
1953 MG TD
2012 Jaguar XJ

[jameshoward]

Nirmal,

The sedans of the period had axles you could use. I would suggest, unless you're hard over on the 3,69, that there are other axles that you could use to increase your chances of finding one. A search here will provide a ton of info on this subject. I've done mine and the site was invaluable.

Ask lots of questions.

Out of interest, what axle do you have now? I swapped a 4,08 for a 3,42. The difference is considerable.

JH

[nirmal]

Hi JH

I presently have a 4.08. As I have an automatic the advice from the Technical Manual ( benefit from our kind sage Cees Klumper) who has done a similar conversion is not to go below 3.69.
I have found a 3.93 on line for $855.

I don't know if this is worth the expense and the bother.

Nirmal
1969 280 SL
1953 MG TD
2012 Jaguar XJ

[GGR]

Going from 4.08 to 3.92 is about 4% difference and I doubt you will feel it. So I don't think it's worth the work and expense.

You can go up to a 3.27:1 ratio. The auto trans starts in second gear so take off from the traffic light may be a bit sluggish unless you shift manually into 1st (position "2"). I think someone came with a system to have the car start into first all the time, but I don't remember how that was done. A search may bring the discussion up. 

[nirmal]

GGR

Thanks for your help.  I have now located a 3.69 differential from 280 SE (116 series). Do you think this is worth the trouble? I find the high rpms while cruising quite annoying.
The cost of the part is $405

Nirmal
1969 280SL
1953 MG TD
2012 Jaguar XJ

[GGR]

The W116 rear axle won't fit the Pagoda. The system is completely different (swing axle on the Pagoda vs fully independent rear suspension on the W116).

[nirmal]

Sorry the part is from a 114. I believe this should be ok.

Nirmal
1969 280 SL
1953 MG TD
2012 Jaguar XJ

[GGR]

Well no. The W114 and W116 systems are similar. And they are the next generation compared to what is in the Pagoda. It won't fit unless heavy structural modifications are made.

[nirmal]

JH

From which series did you get your 3.42

Nirmal
1969 Automatic 280 SL
1953 MG TD
2012 Jaguar XJ

[hkollan]

Hi,

There is no such thing as a 3.42 rear axle for these cars, a 3.46 can
be found in w108s and some of the late two door w111s with the 3.5 liter engine.
Your best bet is to look for w108s with v8s or later injected 6 cylinder models that had the
3.69 ratio axle. 

Hans

[Garry]

I did a 3.46 conversion out of a 108.  It worked well but you have to decide what you want to do with the breathing tube in the diff.  Do a search on Rear end changes and breather tube fixes for how different people fixed the potential oil leak.

Garry

[nirmal]

I have been unable to locate a 3.69 ratio axle. I am apprehensive about installing a 3.27 ratio axle as it may make the car sluggish which is not recommended on the Dubai roads.
Will keep looking locally. Have found a 1969 280S- 6 cylinder with the 130920 engine W108 chassis which may work well as a donor car. May have a lot of usable parts for the 113.
Will check it out later this week.

Nirmal
1969 Automatic 280 SL
1953 MG TD
2012 Jaguar XJ

[jameshoward]

I did a 3.46 conversion out of a 108.  It worked well but you have to decide what you want to do with the breathing tube in the diff.  Do a search on Rear end changes and breather tube fixes for how different people fixed the potential oil leak.

Garry

Normal, that's what my 3,46 came from. The 3,46 seems good. I have solved the problem Garry raises quite simply if you're interested or decide to go down this route.

[jeblack123]

James (Howard),

How did you solve the problem with the tube on your 3.46. I have a 3.27 that I have been delaying installing, but may actually do it this winter. Any help from you or others would be greatly appreaciated.

Thank you,

James (Black)
(The other James)

[jameshoward]

James,

First, I re-drilled the breather into the same place as it is on my 4,08, so that puts it on the small step just above the axle tube. You'll see a flattened portion, but if you're having trouble finding it, let me know and I can dig out a picture. All I did then use two sump plugs to fill the two holes left by the cooling tube. So far I haven't had any issues at all with seepage. If you did want to maintain the sort of effect that the tube provides, you could use a flexible hose. Others have cut into the subframe to make room for the tube. I would personally advise against that.

Note that the breather on the 4,08 I had has a conical thread, thus drilling a new place for it proves interesting. Finally, if you do decide to drill a place for the correct breather, take precautions to catch the swarf, so use a greased bit and then consider flushing out the axle tube to remove any contamination.

I'm moving house at the moment, so don't have access to my computer for pictures, but let me know if none of this makes sense and I'll see what I can find.

JH

[ja17]

Be careful to check the ratio, most of the 6cyl W108 sedans used the 4.08 and 3:90 also. The W108 sedans with V-8 engines have the ratios you need. Also you cannot use a W109 sedan with air suspension.

[nirmal]

I was looking to get the rear end from a 1973 280SE 4.5 which is a V8 engine. Unfortunately the junkyard wanted to sell the complete car about $2500 as it was a running car (although in poor condition).

 So I bought the 3.27 pinion and crown from Gael and will fix it sometime in December. I don't know if the rear bearings will also need to be changed.

Nirmal
Dubai

[jameshoward]

If you mean the wheel bearings, I'd probably change them unless you know how old the others are. It's dead easy and although the swing axle bearing is expensive, the other side is cheap as chips. If you mean the internal bearings, then you may want to do a bit more thinking.

[Naj ✝︎]

Nirmal,

AFAIK, an MB 3-27 crown wheel will not fit in the Pagoda pumpkin (Diff casing) without machining out the casing.

maybe you have a cwp from a different manufacturer?

naj

[GGR]

It will fit, see discussion here: http://www.peachparts.com/shopforum/vintage-mercedes/312919-w108-differential-ring-pinion-change.html

We also had a discussion on this with Gernold of SL Tech at our last gathering at Tom's place, and he told us he's having this done regularly for his clients. He said some grinding may be needed for clearance purposes for the pinion but not all the time. As explained in the thread above, I think there are good chances this can be avoided if the race of the front pinion bearing is fitted after engaging the pinion, to allow for more wiggle room.

I think confusion comes from the early Pagodas that were using smaller pumpkins. Then it may be an issue, but not on Nirmal's Model Year.