What to do, what to do?

[Merc_Girl]

Hi folk
So, I’m in a conundrum

I’ve made a decision that I will change my 4 speed gearbox for something else, as engine a little too ‘revy’, which becomes draining on long tourneys. To add to that, super unleaded fuel now seems to cost more than diesel, whereas before the cost was between    the new unleaded and diesel (does anyone know why that has happened!!). Anyway, suffice to say, fuel economy is now starting to raise its evil head!

I’m therefore seeking the wiseness of fellow pagoda on where who may have well already ventured down this route.
To note Bessie has the 2.3l engine

Mindful there have been lots of discussions and articles on this, so I thought a poll may be quicker.

I’m erring on the side of the 5 speed gearbox, as pagodas had had the option of a 5 speed gearbox.
But then again, if I’m going to that expense to fit, should I just bite the bullet and get a 6 speed, given I have already gone off original with my heated seats, Bluetooth, usb chargers etc. but then again, for a 2.3l engine, would there be any noticeable benefits.

So, my decision is in your hands!

[Pawel66]

Has it been discussed or perhaps you have discussed with someone how 230SL will cope with the ratio on the gear of 6 speed Getrag (this is probably what you are looking at? Would she manage all right?

[Paul & Dolly]

Or just change the rear axle ratio?

What is your current mpg?

Paul

[MikeSimon]

I concur with Paul. If I have a vehicle that appears too buzzy at highway speeds, the first thing I look at are the possibilities of changing final drive ratio. Less effort, less expensive than digging into a transmission change.

[mdsalemi]

Wait a second…

Isn’t the proper answer related to the final drive ratios?  We’re not provided with that information, so it’s kind of difficult to make a judgment.

In the five speed transmission, you have four gears and an overdrive fifth speed basically. In the six speed transmission if the six speed is also an overdrive, how does it relate to the overdrive in the five speed? If it’s about the same all the six speed is going to buy you is more shifting during normal driving…

Or am I missing something?

I don’t care what kind of rear axle ratio or transmission you put in a pagoda, you’re not going to emulate the drive on long distances with a modern vehicle. My daily drivers are generally turning around 2000 RPM at 80 miles an hour. The air conditioning works perfectly and the noise level is very low…

[Jordan]

Just my 2c but before you go spending any money it would be worthwhile finding someone that has a 5 speed and someone that has a 3.27 rear end and asking if you can try them out for a drive.  Doesn't matter if they are hours away it will be time well spent.  Then you can decide if either of those options are right for you or maybe they aren't and you have saved yourself a tonne of money.

[Paul & Dolly]

Hi Katie, the following is from another member
Peter h
He has lots of knowledge of this

All conversions are now difficult to obtain and expensive.
The getrag 5 speed gearbox or a 3.46 rear axle are hard to find. Both will not be available for less than 8000 euros with manufacture and installation. I would put a 5 gear in a 4 gear and a 3.46 axle in an automatic.

He recently took me out in his Getrag 5 speeder and also his Auto,both fantastic cars he has modified.

Paul

[Cees Klumper]

Just change the rear differential - I did on mine and it lowered the revs just the right amount (I went from 4.08 to 3.69). Cost me under $1,000 differential swap + installation, mind you this is 15+ years ago.

[Davek1]

Hi merc girl, I replaced my 4.08 last year to a 3.27, best thing I ever did. The noise at 60mph was just to much, could not listen to the radio or talk to the Mrs. I have a 280sl so not sure if a 230sl could cope with such a low ratio.
Also the 3.27 rear end is so hard to find in the UK. If you are interested in a rear end swap I would suggest contacting Adam at Quirky classics here in the UK who breaks w108s and usually has various rear end around.

[Peter]

To go from 4,08 to 3,27 will lower the RPM by 20%.
Big question is if the 230SL engine can handle this.
If completely restores maybe, but a 280SL engine is recommended.
If never restored, I doubt it.
 

 .

[Garry]

I installed a Getrag five speed and also changed the rear axle from a 4.08 to a 3.69. 

It was a mistake to do both, the final ratios were too low and the motor strained.  I would recommend one or the other.  If you want to save money then just the rear axle ratio change is the way to go.  However, the five speed Getrag was nice to drive.

I was then lucky to be able to purchaser one of the ZF reproduction gear boxes when they first offered them which i eventually sold with but not installed in the car.     

[BobH]

Surely Katie should see what rear diff ratio she currently has fitted, as far as i know European cars were supplied with 3.75, unless ordered with an option, i may be wrong

If Katie's car already has 3.75, would changing the diff make much of a difference?

[thelews]

you know, they were driven long and hard in the day, as they were designed to do.  Low rpms are a modern thing.  I drove a little 4 banger 1972 BMW 2002 1130 miles mostly at 90 mph, about 14 hours in 1973.  Can't say it even occurred to me then to think about engine revs, and she ran smooth as silk. 

PO of my car, a '67 250 SL, drove it 375 miles in 4 hours back in the day in California.

[Merc_Girl]

Silly question
So how does one know what rear axel one’s car has?

[Cees Klumper]

The ratio # is stamped into the differential on a flat side surface, so you'll need to get underneath the car to see it. May have to clear off some grime/dirt first.
I agree that if the current ratio is 3.75 then going to a 3.69 would be rather pointless. But then I would suggest to just leave it all alone, focus on finding any air gaps between the cabin and the engine compartment that could be letting excess noise in, and living with the higher rpms that these engines are designed for. My 4.08 I thought was over the top, but at 3.69 it's quite ok.

[mdsalemi]

Our friend and member AlexD, from NC, whose car was in a severe crash a year ago, has his 250SL at Motorwerks in Michigan being repaired. It’s almost done.

Since his OEM standard 4-speed needed a rebuild he opted to install a 5-speed Tremec (f/k/a Borg-Warner). He bought a complete kit and Motorwerks is doing the installation now. Kit comes from www.thedrivenman.com

[Pawel66]

Not being an expert on this I am wondering how would 230SL engine manage with reduced diff ratios or gear ratios. Most of the mods I am reading below is for 280SL.

On the other hand I read before discussions about Air Conditioning in 230Sl and there were voices from experienced people about AC being felt on 230SL.

I have not experienced personally any of the above on 230SL, so no clue.

[Jordan]

Here is a pic of where to find it (circled in red).  Not my car, just did a grab from a car on BaT.

[Raymond]

I pioneered the T-5 conversion.  The article is in one of the Pagoda World magazines.  (2009?)  Bud's Benz made a great kit for it and that's what Dirveman copied.  My 280's rear ratio is 4.08.  My T-5 has the final drive from a Mustang and is 0.72.  I can use it anywhere over 35 mph.  My highway revs went from 4,000 at 70 to 3,000 at 72.  Highway mileage improved to significantly.  I didn't do it for fuel.  I did it for the driving experience.  First gear in the factory Getrag 72 4-speed is way to short for my taste.  I don't do a lot of stump pulling.  The T-5 first gear is much more traffic friendly.  In the US, the Getrag 275 (non-dogleg used in BMWs) is pretty rare, but T-5s abound and parts are readily available.  In England, I'm not sure of your T-5 options, but there is a Getrag 275 conversion that might be more practical. 

That said, if all you want is to lower the highway rpm, the rear ratio would be the more simple option.  That would also help that high ratio first gear.  As for a 6-speed, I'd want to know how the gear ratios are spaced, how low the rpms would be, and how much room in the tunnel there is for a box that big.  I know with the T-5 conversion, everything is reversible.  Also, on the T-5 the reverse location is the same as the ZF, so I got a shift knob with the correct pattern.

[rwmastel]

A lot of people praise the 3.27 conversion.  Is it safe to assume most differential conversions are performed by swapping the whole rear axle?  Or, do they literally swap out the gearing?  I ask because I always hear about the 3.27 being in axles connected to disk brakes.  Not easy swap for 230SL with drum brakes.

By the way, I have a 230SL with 3.75 differential & auto trans and the RPMs never bothered me.

[Scottcorvette]

I have a Getrag 5 speed that I had rebuilt by All Gears, and also the conversion kit from Mark Bull. I'm not sure Im going to go that route now or even get that far so may be willing to sell. I'm not really sure of its value, and I cant remember what it cost me to do. I know it was a fortune because I wound up buying a 6 series BMW project to get it, and the rebuild took forever.

I have the mechanical speedo gear, prop shaft end, new mounts, and I had the conversion kit and all fasteners cad plated, so make me an offer I cant refuse....

[getsmart]

Just to add, my 230sl is an early 1964 manual Australian delivery and it has the original diff which is a 3.75. So I would have thought yours is the same....

R/Joe