Fitting a 250 SL differential in a 230 SL

[graphic66]

I have the dreaded sudden differential failure in my 66' 230 SL with an automatic trans., 4:08 diff, and drum brakes. I have a complete 67' 250 SL parts car with a 4 speed standard trans. and disc brakes. Will these interchange? Can I use my existing brake master cylinder with the disc brakes and required proportioning valve. I cannot find where the ratio on the 250 SL diff is stamped, where would that be? Not that it matters now, whatever it is it is.
   Also, would it be possible to mount my drum brakes on the new axle, replacing the disc brakes, not a great idea, I know, but it would be an option as my brakes are all new and my replacement axle will require all new brake components.
   Or, as another wild option, could I open up the axles and switch out the broken part, the internal UV joint from the 250 to the 230. The axles look different so this is probably not likely.
   I have been through several threads about axle changes and it looks pretty straight forward. Is there any info that I should know proceeding into this job that may not be in other threads.
   It is going to be a long greasy weekend, Now to start ordering parts. 

[JimVillers]

graphic66 ...... Retaining your old brakes would be hard because of  changes to axle housing.  You should be able to use the disk brakes with the regulator valve that you should have on your parts car (000 431 36 12).

[Naj ✝︎]

Hello, graphics66,

Looking at the parts lists, the 250 uv joint will probably not fit the 230. There was talk of the 230 uv joint being smaller.
The axle swap will be much easier. You will also need the emergency brake cables besides the brake valve from the 250.
The diff ratio is usually stamped on the bottom left rib of the diff casing. Have to clean up the flat machined surface as the stamping is not very deep.

Happy fixing 

naj

[graphic66]

Thank you so much for the info so far. I did see looking at parts lists that the parking brake cables will need replaced. I am now looking forward to the job. I will report back with progress and please, if anyone has more advice I would appreciate it. I will be getting a list of needed parts together over the weekend.

[Naj ✝︎]

Worth taking the discs off to check the e-brake shoes and for oil seepage from the diff.
The one stripped down at Blacklick Monday had oil on one side.
Leak from pinion seal  
Also ensure the adjusters have not seized up
naj

[wbain]

The master cyl also needs to be changed because the 230Sl with drums has a check valve where the 250/280SL MC does not.

[graphic66]

Great info so far. I will need to pull the master cylinder off my parts car also. The place where the ratio was marked on my replacement axle has apparently rusted away. Does anyone know of another way of telling the ratio, just out of curiosity really. The axle is going in regardless. The donor is an early US 250SL with a 4 speed, any guesses? 
  The parking brakes look good so far, the calipers look great, no corrosion on the pistons, the rotors look beefy enough to turn a little to clean them up, the pressure modulator looks good. The rubber bushing on the torque arms where they attach to the axle are tight and turn nicely. I think I will leave those and just replace the rubber parts that hook to the car.
   Can I just put the axle in and not worry about alignment because I wont be changing any adjustments to the mounting arms?
   How about the drive shaft? Will that just bolt up, I hope?`

[JimVillers]

The "normal" 250SL rear end ratio was 3.92:1.

[Naj ✝︎]

Does anyone know of another way of telling the ratio, just out of curiosity really. The axle is going in regardless. The donor is an early US 250SL with a 4 speed, any guesses? 
     

Yes, mark the propshaft flange and a stationery point on the casing with paint etc.
Hold one axle flange and turn the other one exactly one turn. (Helper needed)
Count the number of turns on the prop flange as you do this.
You could get 3.75, 3.92, 4.08 etc...

naj

[graphic66]

Where might one find the metal band clamps, the kind with a cotter type pin to tighten them for attaching the parking brake cable to the axle.The ones that go through the torque arm mounts. Used would be fine.
   Also, my 66' 230 Sl has some fibre type exhaust gaskets between the tubular headers and the exhaust pipe. My car has some inserts in the pipe with the fibre gaskets on them. The parts I have seen are just metal rings that seal there, I suspect the tubular headers are different than the cast ones. Does anyone have an idea where to get new do-nut gaskets for this, or has my car been bastardized at some point?

[geezer]

Yes, mark the propshaft flange and a stationery point on the casing with paint etc.
Hold one axle flange and turn the other one exactly one turn. (Helper needed)
Count the number of turns on the prop flange as you do this.
You could get 3.75, 3.92, 4.08 etc...

naj

Keep in mind that holding 1 axle stationary, while turning the other, makes the pinion flange turn twice as fast.  Example: if the flange makes 2 revolutions the ratio would be 4.0 to 1, if it makes 1 1/2 revs the ratio would be 3.0 to 1.

[graphic66]

Yes, I discovered that. I found logical results with two people and some spray paint. Paint a mark on each hub and the pinion. Each person turns a hub in unison and you watch the pinion. I came up with just under 4 turns on an axle. I believe this is a 3.9 something axle.
  And please does anyone know a source for my previously mentioned items, axle straps and exhaust do-nuts?