Highway cruising speed

[Macfly]

Hi all,

I’m casually looking for a SL up to model year 1971 and wondering how they are on US highways. Should I expect to keep up with current day traffic comfortably at 80 mph? Or will she be screaming for mercy? Or too dangerous for such travel?

[mrfatboy]

I used to use my car as a daily driver.  40 miles a day during the week on interstate 5. I would cruise ~70mph @ ~4100 rpm.  No problem hitting 80-100mph (short bursts) for passing and fun. 

I feel it takes more concentration driving at those speeds with a Pagoda than a modern car.  It definitely much noisier🤣

My car is stock. Others here on the forum have changed their rear axle to lower the rpms. I'm sure someone that has done the job can comment.

YMMV

[Macfly]

That begs my follow up question: whether there are 5 speed overdrive transmissions available (manual)?

[mrfatboy]

do a search on "ZF 5 speed" on this forum. 👍

[Bonnyboy]

I drive on the freeway often and my car seems to like to drive at 75 mph (120 kph).  I am constantly slowing down to 110-105 kph but it just wants to go at 120.    I have a 3.69 rear end and passengers generally find the engine noisy/busy but I am used to it and find it relaxing.  Driving at 100 kph just seems slow for the car.

 

[JamesL]

That begs my follow up question: whether there are 5 speed overdrive transmissions available (manual)?

The engines were built to run at high revs for long periods and max torque is above 3000rpm, if I recall. That’s about 55-60mph for most of us

It’s noisy at speed as housebricks are more aerodynamic and sound deadening is not modern but high revs shouldn’t scare you if the engine is in decent condition. Mine has been down to southern France several times now and will sit at 85/~4250 revs for hours on end very happily.

A 5 speed, or different rear diff can help but is the cost worth it (per mile)?

[prefervintage]

As these cars were designed for the Autobahn and elsewhere, they love to be driven fast! I drive mine all the time on the highway at 70-80 MPH (which is what it takes to keep up with traffic these days in the states, apparently). I was once bold enough 15 years ago to take my pagoda up to 120, and she was she still pulling to go faster! I would just make sure your timing chain doesn't have excessive slop, and that the engine seems in good condition (compression, valves, injectors, etc), and aside from that and routine safety checks on tires, brakes, suspension mounts, drive away happy at sustained highway speeds.

[MikeSimon]

This is what you definitely experience with most European cars of that era: European engine design was based on the objective to produce horsepower through rpm. US automotive engineers designed engines to produce horsepower through displacement/torque. The formula for horsepower : P=M x ω   P= horsepower M= torque  ω = 2𝝅 x n (with n= engine speed) gives the base for this.
Using the displacement, of course, means more fuel consumption, but in the U.S. - contrary to Europe - that was never a big concern. Also U.S. cars were always designed for low end torque, thus providing the infamous drag races on the street. Expect any European car to generally run at a higher rpm level at any highway speed than a U.S. vehicle.

[thelews]

My car cruises effortlessly at 80 mph, one finger on the steering wheel. It has 156K miles on it. It's a joy and I marvel at how well this car performs by today's standards.  I feel this era was some of the best cars MB ever produced.  Sure, it revs high, that's how they were built back then.  And they love it.

The previous owner of my car drove it 350 or so miles in 4 hours, probably in the 1970s.  It's in a post somewhere on this forum.

Even my 190 SL with its little, underpowered 4 banger seems happy to cruise at 70+ mph.

[jeffc280sl]

I suggest you read about the 3,27 axle upgrade.  while our cars were designed in a country with the autobahn is was adapted/setup for the US market.  look at the ratio of auto tranny SL's in the USA.  The car was geared to allow fast starts from stop lights.  first gear in the auto and manual versions is too low.  highway cruising was secondary priority.

read up posts about rear axle upgrades.  my manual trans 280sl performs best with this axle

[JN]

I have my 250 sl up for sale and it has the lower gear ratio for cruising from the factory
Please see the add in items for sale
JN

[mauro12]

I have the 5 speed zf gearbox and the perfect speed for me is about 110kph , around 3500rpm. The car still keeps a good mileage and the engine doesn’t scream too much , but I think this is not the right car to use if you are in a hurry .

[thelews]

  first gear in the auto and manual versions is too low.

I disagree.  I never considered 1st gear in my manual 250 SL too low.  Seems just fine to me and I always use it from starts.  OTOH, 1st gear in my mother's '71 280 SL was for pulling stumps.  What a ridiculous gear and no wonder it only came into play automatically if you floored the car (and chirped shifting to 2nd).  When I decided to get a 113 I specifically looked for a stick for that reason.

[RobSirg]

I have both 250SL and 280SL in manual (why do American's call them standard?.....it's Ok, I think I know  ….and why do they call them "4 speed"....the Auto is also 4 speed?)
I feel my 250SL and 280SL manual are both geared too low in first gear but still driveable. 
I have to agree that first gear in the Auto is kind of ridiculous, but good for a party trick - How many modern auto's can chirp their wheels when changing from 1st to 2nd?......albeit on the other side of the intersection 

[lowpad]

My 230SL has no trouble keeping up with highway speeds up into the high 70s at least.  While it's working hard (it's a European model), it isn't objectionably loud or buzzy, even with the top down.  I never think of not going anywhere even though it's almost as old as I am .... But I'd be curious to know if anyone has installed a more modern DB 5- or 6-speed manual transmission as the original / re-released ZF 5-speeds are practically unobtanium.  Interestingly, 5-speed conversions are very common on BMW CS coupes (ie, E9s) and seem to be relatively inexpensive and not too technically challenging.  I'm surprised that there isn't more of a cottage industry like this for the W113.

[Peter h]

https://youtu.be/mbHd2GPhG-4
5 speed getrag 4.08 axel. 
Speed and good rotation.
Peter

[jeffc280sl]

Some data to consider.  Final gear ratio  ZFs 5-20 .848 5 speed, G72 1.0 4 speed
                                                               stock
Ring and Pinion size    4.08   3.92    3.27    3.92
Tire diameter    26.65
RPM                 4000
Final gear ratio           .848   .848     1         1

Speed MPH               88.26  91.86      93.38   77.9

I can tell you that my 1970 280SL with G72 and 3.27 rear end has plenty of torque/hp to accelerate from 93.38 mph to 100 mph.  The last 2 columns show a mph increase of 15.5 mph from rear end change only

[roberhofer]

Have the 230 SL with the higher ratio. I do like to drive it at 80mph. The engine is revving high though at 4500. At the beginning, I felt sorry for the engine but got used to it. It likes to rev.
I was/am considering though either a different rear axle or modern 6 speed to reduce the revs at this speed.

But to your question: yes, 80mph - no problem. Actually I like do overtake cars uphill since the car is at max power in the 4500 rev range.

[wayne R]

Similiar for myself,like most others,high revs,but loves it, but i would like to mention
something else,that  may interest others,.
I presently have 1965 automatic  4.08 diff,this little riper goes like a rocket,  but about 12 -13 years ago,
i owned a 1971 280SL  stick manual box,all original, except white Nardi steering wheel, had only 78000 miles on
speedo,--ex New Mexico--,very late serial number, and that Pagoda was not a patch on this present 230 SL,
and i dont really know why, this 230 SL seems to rev alot freeer, and so feels better.
This 230SL has  122000miles on it and the head has never been removed from new.   regards Wayne.
Top photo is 280SL in New Zealand---bottom is 230SL Australia.

[SEB]

Some data to consider.  Final gear ratio  ZFs 5-20 .848 5 speed, G72 1.0 4 speed
                                                               stock
Ring and Pinion size    4.08   3.92    3.27    3.92
Tire diameter    26.65
RPM                 4000
Final gear ratio           .848   .848     1         1

Speed MPH               88.26  91.86      93.38   77.9

Hello Jeff
many thanks for your empiric data. So it looks, that more better is to change the ratio, on the rear axis, than the gear box?
I mean for cruising not rally driving :-)
Unfortunately this ratio is hard to get in Germany. I think it was only build for the W108 with the 4.5 engine US market?
Sebastian

[Desertpagoda]

yes, the axle from a 4.5 makes a nice improvement in cruising rpm, I have one in my '66 auto. I think I remember that the final ratio of a MB 4spd and a ZF 5spd are very similar?

[TheEngineer]

I did change the rear axle to 3.27 years ago and it made a better driving car. It is also more quiet at cruising speed. But what I really like, is to drive very slow: my car does about 6 MPH at idle (500RPM) and it very pleasant to drive at that speed around my neighborhood with the top down. Yes, I am showing off. The car is almost silent and people wave at me. We have Alki Beach, a long level road along the water for miles. Girls playing volleyball, people riding bicycles and I am driving slow and noiseless. It doesn't get much better than that

[Benz Dr.]

yes, the axle from a 4.5 makes a nice improvement in cruising rpm, I have one in my '66 auto. I think I remember that the final ratio of a MB 4spd and a ZF 5spd are very similar?

Standard final drive ratio with a ZF is around 3.46  which is just about right for the torque band on a 113.