First off I see there is a 107 2.72 rear diff that should fit the 123....


More importantly while doing my car this weekend I saw that the inner diff horizontal gearing has a tooth with good chunk taken out of it. The big ring and connecting ring show no wear. How concerned should I be about this? This part only rotates when there is slip right?

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1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

Find the chunk then don't worry about it too much.

Just try to restrain your burnouts.

I do believe the 107 diff should fit. As long it has the four 19mm bolt studs and rear diff mount on the cover.

With that said, wouldn't a 2.72 be a bit too tall for a 4 speed manual?

I got a good 3.07 and speedo combo that should be perfect if you want to make a deal.

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1983 123.133 California
- GreaseCar Veg System

Here is some helpful information:

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Peach Parts W124.128 User Group.

80 280SL
85 300SD
87 300TD
92 300D 2.5 Turbo
92 300TE 4Matic

I'm not familiar with Mercedes differentials specifically, they're not limited slip differentials are they?

Are you talking about the small bevel pinions or larger bevel gears inside the differential (the bevel gears are fixed to the axle shafts, and the bevel pinions are mounted to the differential carrier gear and mate to the two bevel gears)? Because the small bevel pinions rotate whenever there is relative movement between the two rear wheels. So, like, every time you turn.

Also, the bevel pinions transmit the full driving load from the carrier gear (which is driven by the drive shaft) to the bevel gears (fixed to the axles). So if that tooth with the missing chuck happens to be engaged when you're driving, you'll have much higher stresses in the remaining tooth, so it could be a problem.

All of this could be WAY off if I misunderstood your initial question. I'm just going off of how differentials work in general. And, for goodness sake, find the chuck of tooth and put it on your shelf

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

Are you talking about the spider gears (US name)? I think that they can be changed while in the car but don't hold me to it. They are important in that they allow the rear to turn without sliding the outer tire or spinning the inner tire. In a turn the rear tracks on two different radius.When they break the car will no longer move. (ask me how I know)

Good luck and how is the motor home coming along?
Robert

Just as I thought, the smaller internal gears is where the damage is. Almost certainly from burnouts as my year old flex disks indicate.

__________________
http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

That 3.27 would be totally perfect, IMHO. Too bad the speedo would never be accurate.

Can you not change the speedo drive gears in the transmission like you can with American cars?

If not, you can also get custom-cut external gearboxes that go inline with the cable. I have one on my '57 Chevy and had one on my motorhome.



http://www.gaugeguys.com/

http://www.speedometershop.com/ratio.html

http://www.speedograph-richfield.com/html/minature_gearbox.html

Nope. Mercedes uses the same ratio in all their transmissions. The difference is in the speedometer which is determined by the rear end ratio.

That cable gear box will work. You first have to determine what is the percentage your off through the speed ranges. Then get a box that is specifically calibrated for that percentage, hook it up and the correction is made.

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1983 123.133 California
- GreaseCar Veg System