How fast it too fast for a 65 sl

[Surfer65sl]

Hello Members,

As you are all well aware, traffic on interstates flows at 80mph...once in awhile my 65 230sl 4 speed slips out of gear.  I simply put it back in gear and keep the car in the 3500-3700 rpm range on highways.  Weren't these cars made to be driven at higher rpm's?  Is that too much stress for an original engine and what can be done to rectify this occasional slipping out of the gear box on my manual.  A compression test was completed when i purchased and everything was A-okay.

My mechanic suggested I do nothing to the engine not even clean it as he believes a worn original is more appealing in a resale.   

Thanks as always for the great site and advice.

Matt 

[thelews]

You have a transmission problem, not an engine problem.  I've driven mine 95mph with no issues, in fact, it likes it.  Just make sure your tires are good.

[w113dude]

Matt,

There are two possibilities,
A) the gear box lever needs to be re-adjusted so that it makes the gear snap in to place properly
B) the metal push piece that puts in gear inside the transmission has worn out & should be fixed, I would look in to A as it's a much easier fix.

[Cees Klumper]

You should be able to cruise at speeds up to and beyond 90 MPH all day if need be, so long as everything is well-maintained technically.

[jameshoward]

John,

What ratio is your rear axle? I currently have a 4,08 on a (US) 230 and I can't cruise at 95 comfortably. I've got a 3,46 that I'm hoping to be able to change to, although it's going to cost more than I had first hoped. I hope to complete the change before the Europe event.

JH

[thelews]

I'd have to go look, but at 80 she's turning 4500 or so, if I recall.  Previous owner ran it 100 mph. for hours at a time, 375 miles in 4 hours.  The issue with your "comfort" is more in your mind than the car mechanically.  You're comparing to modern gear ratios for fuel economy.

[Naj ✝︎]

17.xx miles per 1000 rpm sound about right for a 4..08 or 3.92

5000 rpm @~85mph

naj

[graphic66]

With a 3.92 ratio and 205/70/14 tires at 5000 Rpm you are traveling at 96 MPH, with a 4.08 you are going 92 MPH at 5000 Rpm. With a 3.46 ratio you are going 108 Mph at 5000Rpm, if you have enough horsepower to ever get there as these cars are designed to rev higher than most cars and have very high RPM to horsepower and torque peaks compared to most street cars. With a higher rear end ratio you could end up with a sluggish unresponsive car compared to what it was made to be. I love the sound of my engine reving as it was made to be. I did switch from a 4.08 to the 3.92 as I had sudden diff failure. I love the disc brakes compared to the drum, but I liked the 4.08 better. I can no longer get rubber when I shift from 1st. to 2nd while accelerating hard. The car is just a little less "chipper" off the line.
   Your transmission has most likely worn shafts and bushings causing it to pop out of gear, maybe someone put gear oil in there instead of the recommended ATF, it may be worth a look to help keep any further wear to a minimum.

[ja17]

Mercedes engines of the era were designed to run at redline for extended periods of time. No I am not suggesting that you take a tired worn engine and doing this.  However if your engine is healthy with good oil pressure, timing chain, compression, etc, you have little to fear. In fact these engine often benefit from a good "Italian tune up". 

[Naj ✝︎]

 

[J. Huber]

Then there is my seemingly 2.85 rear end.... 95 mph at 4400   

[Benz Dr.]

All of this depends on engine condition and you can't tell by a simple compression test. It will give you some idea but I tend to go by several factors before I recomend any high or prolonged RPM useage. If it's an old original engine and it looks beat up, I say NO WAY!

I've had several engines fail by higher RPM shifting or prolonged RPM over 4,000 .
 In one case a rod bearing let go. I could hear a faint rattle that got louder as I drove along after taking it up over 4.500 just one time while shifting. This was on a 220SEb coupe which is very similar to a 230SL engine. This engine ran well enough but actually had a lot of wear on all componets.
The other engine failure was on a 250SE coupe which is the same engine as a 250SL. In this case I was on I 75 coming back from the Mountains. I managed to get home with the car but it failed the next day after I got home. This engine also ran well but I never drove it hard and kept it around 3500 or less for the year I drove it. On the interstate, I had to keep it at 4,000 or more to keep up with traffic. Thinking I was OK I did that for hours at a time. The engine diied from terminal    '' death rattle ''   and I still have the piston that I use as an example of what can happen. This engine is now in the Red Rocket after being rebuilt. In this car I never have to drive it more than 3,500 RPM to keep up with traffic because it has a 5 speed. That alone is worth a lot in terms of engine wear and longevity.
Before I changed the engine in my car it also died from death rattle and it never saw high RPM. 

So, how fast it is too fast? You won't ever know that until it's too late if you believe any speed is safe. Yes, you can spin these engines very fast but only if they're in solid condition. Any cylinder or wear around the piston rings and you will eventually break a top piston ring at high RPM. Keep it under 3,000 and you can drive even a worn engine for a very long time.

The one thing I'd bet my reputation on is you CAN'T run any of these engines at high RPM's for extended periods IF they're worn out - they WILL spit out a piston or rod bearing.

[ja17]

Hello,
I feel that not being able to take these cars out for a good run is like making a thouroughbred race horse pull a flower cart. If your engine is sick, plan on fixing it or trade it in on a W113 that is healthy.

[Ulf]

Speed is very much a matter of the surroundings - I would much rather go 70 mph on a twisting road through a beautiful landscape than 100 on a wide highway (although I've done that for 3 hours in a row through heavy rain and the car performed wonderfully).

[ja17]

Hello Ulf,

I agree, "g" forces in a turn is much more exhilarating than just straight line speed. Being able to use all those rpms to power in and out of turns is part of the experience.