Not Your Average 3.27 Axle Question

[IXLR8]

I'm in the throes of a complete restoraation on a 1965 230SL.

In lieu of finding a replacement axle from a 280 SE 4.5 with its own transportation, restoration, brake and cost issues, etc., would it be better to merely change the gears in the existing rear end?

Specifically, would this require both a pinion and ring change or a pinion change only?

What would be the ballpark difference in cost for the new gears vs. a used axle?

Thanks in advance for any comments.

Joe

[Benz Dr.]

Most 230SL's have 3:75 gearing - stick with that.
If it's 4:08 you might want to get a 3:75 but the 3:27 is pretty high gearing for that car. If the engine was rebuilt with the low compression pistons you will want 4:08.
 
Don't bother with the internal gear change - it's far too much work and most won't have the special equipment to do it right.

[jameshoward]

Dan,

Most 230SL's have 3:75 gearing - stick with that.
If it's 4:08 you might want to get a 3:75 but the 3:27 is pretty high gearing for that car.

That's interesting as many of the US shipped 230's I've come across have been 4,08 (like mine). I've finally found a 3,46 to replace my axle with, but to be honest if my car was born with a 3,75 I'd never have bothered! Was there a point where US cars changed from a 3,75 to the 4,08, or was 4,08 an option that some plumed for? I've always found my diff to be great on take off, but just utterly lousy for touring around Europe, hence the desire to change to something a bit lower.

My car has really poor compression (105-110 across the range - I've bored you with that issue before!) do you think that would explain why someone might have opted with 4,08 on my car? I've always wondered why it runs well with what would seem to be very poor compression by 113 standards. (Uses no oil!!)

JH

[ja17]

Hello,

The 3.27 gear set is to large to fit in your original diff anyway.

[graphic66]

The 230SL engine is designed to run at high RPM's. Trying to Amercanize this engine will just make it run out of the RPM range it was made to run at. Peak torque on a big American V8 is way lower RPM than these finely tuned engines. Peak horsepower is, from memory around 5500 RPM with peak torque very close at around 5000 RPM. This is why the low gearing, to keep you in the sweet spot of performance. It is how some very smart and well educated engineers made these superb cars perform at a rate of 1HP for each cubic inch. Switching to a higher gear ratio may sound good but in my opinion you will end up with a lethargic car that doesn't have enough horsepower to run at that gearing. You can just keep gearing higher and keep going faster, that requires an increase in horsepower to do that. You get used to the high reving and realise after a while that they were made to do this. Find an American v8 made in 1966 that could rev to 5500 RPM all day long, they were tuned way differently. That is why they were geared to run at 70MPH and turn under 3000RPM, because the peak HP and torque were way lower RPM. These cars love to rev and if they are in good shape they will run all day at 80MPH without any problem, that is how they were made.
   The 4:08 was for the American market because we wanted takeoff power. The higher ratio's were more for Autobhan cruising at high speeds. Most driving in todays World is under 80MPH and a 4:08 axle does that just perfect.

[66andBlue]

... Was there a point where US cars changed from a 3,75 to the 4,08, or was 4,08 an option that some plumed for? ..

Hello James,
here are the details when and in which cars these differentials were installed:
http://www.pagode.info/22.htm
I would love to find the standard 3.69 axle that was installed after Nov. 1969 in all 280SL except those shipped to the USA - perfect ratio for a Pagoda.

[PnHi]

Hello James,
here are the details when and in which cars these differentials were installed:
http://www.pagode.info/22.htm
I would love to find the standard 3.69 axle that was installed after Nov. 1969 in all 280SL except those shipped to the USA - perfect ratio for a Pagoda.

Rough Translation:

3,69... Factory-installed first on special wish into all 250 SL & 280 SL inserted, afterwards starting from 27,11,69 standard ex factory with 280 SL Exception: Into 280 SL for the USA export factory-installed to 1.7.69 `4.08 axles and starting from 1.7.69 `3.92 axles were built. 280 SL with ZF 5-Gang transmission were delivered factory-installed to 27.11.69 `with 4,08 axle and starting from 12.11.69 `with 3,92 axle.

3,75...  Factory-installed in series built into nearly all 230 SL Exception: Into 230 SL with ZF 5-Gang transmission was built the 4.08 axle.

3,92...  Factory-installed in series built into all 250 SL & 280 SL, afterwards starting from that 27.11.69 `only on special wish for 280 SL available. Factory-installed built starting from that 27.11.69 `into all 280 SL with ZF 5 course transmission. Exceptions: The 280 SL for the USA export had inserted the 4.08 axle to 1.7.69 `factory-installed. Only starting from that 1.7.69 `in 280 SL factory-installed axle was inserted the 3.92.

4,08...  Factory-installed built into most USA export of vehicles, as well as in connection with the ZF 5-Gang transmission Exceptions: 230 SL in the USA export execution were delivered factory-installed with 3,75 axle. 250 SL in the USA export execution were delivered factory-installed with 3,92 axle. 280 SL in the USA export execution were delivered factory-installed starting from 1.7.69 `with 3,92 axle. 280 SL with ZF 5-Gang transmission were delivered starting from 27.11.69 `with 3,92 axle.

[graphic66]

My US delivered '66 230SL came with a 4:08 diff and automatic trans. from the factory, would that have been a special order? I blew that unit and installed the more robust looking 3:92 disc brake axle from my '67 250SL, hardly any difference, I was glad of that.
   I just love how these great engines sing in there power band. It does really scream, when I test drove it I redlined it in second and my friend, the seller asked that I not do that again. I later realised it really runs well reving it. Of course you are going to wear things quicker and break more stuff, but that is just how it is. And of course most of the time I find myself babying my precious car but, every now and then you just have to show those mini vans what for!