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  #1  
Old 05-13-2014, 11:04 AM
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Near-flex disk failure

I almost had the rear doughnut go out on my 72 220d. Needless to say, I'd like to replace them. I've researched the procedure and it seems simple enough, but unfortunately the partial failure of the disk also ruined the differential pinion yoke (I believe that's what it's called...). I can't seem to find too much about replacing these, but in threads where people have replaced a leaking pinion seal (mine is fine!) I see mentions about a crush spacer that has to be done juuuuust right or the pinion nut preload will be incorrect and burn up/break the pinion.

If I'm just pulling/replacing the yoke, is this something I need to worry about? Also, from what I can tell, I need a 12-point 30mm socket with some way to turn it around the shaft, correct? While I'm here, what's involved with replacing the driveshaft centering bushing? I almost hate to not replace it while I'm under there since it's almost certainly the original.

Thanks,
Brandon
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1963 Ford Falcon Convertible
1972 220D 4-speed
1972 280SE
1973 350SL 3.5
1986 190D 2.5 5-speed
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  #2  
Old 05-13-2014, 03:37 PM
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Officially yes!

This is something you need to worry about. The tightness of the pinion bearings is very important. Too tight and your bearings are more likely to fail before their expected end of life (bearings are rated for a number of hours based on their load among other things). Too loose and the effect of the shuttling backwards and forwards of the pinion get exaggerated when power is applied / released from the drive line.

If you follow the procedure in the FSM for bearing replacement (which you would probably be wise to change now as a precautionary measure) you will see that that method is to measure the shaft friction before you dismantle the assembly. The idea is that you tighten the new nut (on your new yoke) until you achieve the same friction. There is most likely a minimum friction that should be achieved.

If you don't have a W114/W115 FSM then use the W123 one - I think it is the same part.

Tips for measuring pinion shaft friction (as well as a whole lot of other stuff that isn't directly relevant) is given here =>

The W201 differential refresh thread
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!

Don't leave that there - I'll take it to bits!
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  #3  
Old 05-13-2014, 05:16 PM
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Thanks for the reply. It's not what I wanted to hear, but pretty much what I expected. In the interest of getting the car back on the road as soon as possible, I have another option; a nearby junkyard has a 1976 230.4 (W115) that I could possibly get the diff from. According to this site, that car should have a 3.69 final drive ratio, while my car has a 3.92. This would obviously throw off my speedo, so what it boils down to is how much work changing the speedo gearing vs putting a new yoke (and probably bearings) is. I'm leaning to the side of the diff swap, but there's the cost factor of messing with the speedometer in there as well. Thoughts?

Thanks,
Brandon
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1963 Ford Falcon Convertible
1972 220D 4-speed
1972 280SE
1973 350SL 3.5
1986 190D 2.5 5-speed
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  #4  
Old 05-14-2014, 12:59 AM
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Well according to the information on the Russian EPC North America got a 3.92 rear end on the 1976 230.4

See the EPC diagrams via EverythingBenz - Mercedes-Benz Forum and Web Search Using Google

I'd go and see the differential on the car in question

Scrape off the lower left hand corner of the diff casing right next to the rear cover to see the marking for the final drive ratio. You could be in luck.
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!

Don't leave that there - I'll take it to bits!
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  #5  
Old 05-14-2014, 05:51 AM
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Join Date: Apr 2014
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shure about that 3.92?
the 230.6 i have had that ratio thou, and i am from Europe, so might be different.

either way, how far of is your current speedometer? is it spot on, or shows a tad to much (as al of mine has) it might be that your current speedometer will show a more correct speed with a 3.69 than the current 3.92.

the 220d isnt fast, but it can handle a 3.69differential without much problems, giving you a nicer less screamy ride RPM wise. aswell as a tad better MPG.

you could always get the speedo from the 230.4 at the junkyard "worst" case scenario.

/me that has that mbturbo.com site.
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  #6  
Old 05-14-2014, 06:58 AM
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Quote:
Originally Posted by swampmonkey View Post
shure about that 3.92?
the 230.6 i have had that ratio thou, and i am from Europe, so might be different.

...
That's what the Russian EPC says - 3.69 in Europe but 3.92 in the US of A {This might not be reliable information - sometimes there's a different differential for manual and automatic transmissions}

Still in either case - what ever (!) - it is best to check the one on the car in the scrap yard it could have had anything fitted to it in a previous life; you can never tell.

{I'd be tempted to see if the damn thing worked first before calibrating speedometers - these days those smart phones have GPS speed indicating aps anyway so a temporary solution can be made}
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!

Don't leave that there - I'll take it to bits!
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  #7  
Old 05-16-2014, 05:51 PM
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Join Date: Nov 2012
Location: Nashville, TN
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Sorry about being quiet these past few days, I just got back from the junkyard and the 230.4 did have a 3.92 in there. I wouldn't have been opposed to a 3.69 since my car does mostly highway miles, but the gauge cluster was long gone so no speedo from there.

One more short question, should I also pull the driveshaft to keep on hand as a spare? My car has had a harder life than the scrapped one did, and since learning that the universal joints aren't meant to be serviced the thought of having a super-clean one (for $35) ready to toss in is somewhat tempting.

Looking back, I should've taken pictures of it. It had been hit in the front, but otherwise it was in very good shape with almost no rust. I appreciate its sacrifice as I've gotten a lot of good stuff off of it
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1963 Ford Falcon Convertible
1972 220D 4-speed
1972 280SE
1973 350SL 3.5
1986 190D 2.5 5-speed
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  #8  
Old 05-17-2014, 02:12 AM
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Gettin' outa chokey
 
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If you have storage space 35 USD seems like a great deal to me
__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!

Don't leave that there - I'll take it to bits!
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