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Transmission Ratios

This component is part of Transmission and Clutch.

Definition

Define the component. Include, if known, the german language word for the component, as well as the English or American equivalent. Show a picture, a diagram.

  • Its technical name & common name(s)
  • part # - start year & end year
  • which area it belongs to - engine, transmission, body, injection etc, link back to the relevant section

Function

Describe, in general terms the function of this component. Meaning what is it there for and what role it plays. Describe how it works, the inside mechanism. Use diagrams to explain.

Maintenance

Describe common maintenance procedures, and common faults that may occur. Describe how these may be diagnosed and resolved. Again, include diagrams, photographs and explanations. Where possible, include measures, tolerances, weights etc.

  • Symptoms when it faults
  • How to test if it is faulty - what tools to use
  • How to fix / change

Link to related components where appropriate.

Old Yahoo content

The following is the content from the old Yahoo documents on the site. It needs to be structured and edited in the correct sections of the entire document. After moving particular content to its correct place in the manual, please delete it here.


I would like to have a five speed, but based on my math, with a little help from “Essential Mercedes SL" I do not believe the final drive ratio is that different between the four and five speed. The final ratio on a four speed is 1:1 and on a five speed is .848:1, this would decrease RPm's by about 15% or take you from 4500 down to 3825. Nice to have but a far cry from a comparison of 4500 rpm vs in the mid 2000's!

The best you can do with what is available is the rear differential from the 108 chassis 280-4.5. This is 3:27. Most 113's are 3:92 to 4:08's. Some 3:69', but not many. The 108 is enclosed swing axle and will fit. The other thing to help is to stay with the Euro 80 aspect ratio tires. Michelin Rain Force has this profile and works out well. The math will tell you exactly where you wind up. Best to use a rolling 1 [one] revolution measurement on the ground for the math. I have done one of mine and am very pleased. With a 3:27 diff. and a 25.5" diam tire, the rpm at 65 mph is about 2800.

I wonder if other MB 5-speeds can be fitted? From my Haynes manual it appears as though 5-speeds were found in 250se, 250 ce, 250c, as well as 280se/8, though they appear to have different lever arrangements. Anyone know what’s possible?

Mercedes Benz introduced the new style side shifter transmission type G76 in may 1969 on the 108 and 111 bodied cars, but stayed with the G72 and the ZF until the end of production on the W113 chassis cars. I suspect an interference problem inside the transmission tunnel. The later transmissions will definitely bolt up to the engine, but there has to be an explanation as to why MB never fitted them to the W113 cars. Has anybody ever tried to fit any other transmission inside the tunnel?

Pete Lesler: if you are concerned about high revs at highway speeds, a cheaper way out than installing a 5-speed is to install a 3:27 out of a 280SE 4.5 sedan, a 3:46 out of a 3.5 sedan or a 3:69 out of a 3.5 coupe or sedan. The track width and mounting are the same, except for the emergency brake cables which must be swapped. These must come out of a car without air suspension.

The following information is from Mercedes itself, taken from their owner's manuals or technical data books, which if you don't own, you should: they are still available in reprint from MB here in the US. The 230SL was originally fitted with: 3.75 (international), 4.08 (5-speed AND U.S. spec). The 250SL and 280SL's were originally fitted with: 3.92 (international), 3.69 (optional for "sporting events"), 4.08 (for 5-speed AND US spec). The manual also has a complex chart indicating the tach rate, which is the number of revolutions of the drive shaft per meter of distance travelled, with 185-14 tires, properly inflated, and with full "permissable" load. It indicates that this rate is the same for auto transmission, 4-speed and right and left hand drive models. It should go without saying that the taller gearing of the US spec models has to do with maintaining acceleration capabilities with the reduced horsepower, and the fact that U.S. highway speeds were always lower than in Europe. There is also a chart regarding "engine speed" at 100km/h, which for auto tranmission models is the RPM's expressed as a range depending on engine load. For the 230's, it is 3190 rpm to 3380; 250's: 3140 to 3530; and 280's: 3140 to 3490. Standard transmissions were not a range, but were listed for 4th gear (1:1) as 3475 RPM with the 5 speed for all models; 4 speed/230 @ 3190; the 250/280 (3.92) @ 3340 or 3140 with the 3.69. Interestingly enough, across the entire Mercedes passenger car line at the time, across all transmissions and rear axle ratios, you'll find an amazingly tight grouping all around 3200 RPM. Clearly a consistency of engine design. To use my own vernacular, if you have rear axle ratios other than those mentioned for the cars mentioned, you have something "bogus", and it is to be suspect. The same books also indicate that all 230/250/280's engines reach peak HP at about 5500 rpm, and peak torque at 4500 rpm (the numbers vary slightly). That should give you an idea of why things were geared as they are. Don't forget to factor in US specs; these were not just emission controls but other things which added weight to the base vehicle, and things which also did exist pre-1968.

Arthur Dalton: Many 113 owner do use the 3:27 rear. It is as close as you can get to the 5 speed w/a 4 speed trans. I have both and they have their place , but I am very satisfied with the performance of the 3:27/4 speed combo. It took me many years to justify trying, and now I am happy I listened to others who recommended the change.

Michael Salemi: Arthur is right in that changing to a 3.27 rear end will effectively turn your 4-speed into an OD transmission. Wat he neglects to mention is that it also effectively turns your 4-speed into a 3-speed transmission, and while it gives you less than 1:1 (i.e. overdrive) in your 4th gear, it also negatively impacts the acceleration through the first three gears. Arthur may be satisfied with overall performance of his desired combination, but there are probably many of you already quietly dissatisfied with the acceleration of the 113's. There's no free lunch here. My own opinion is that if you don't like the way the "normal" 113 drives, be it handling, RPM's or what have you, perhaps another car is in order. So what if it runs high RPM's at cruise? That's the way it was designed. I'd have to disagree with the concept of changing the rear axle ratio to a non-standard one unless you save the old pieces for the next owner!

Arthur again: I can assure you that originality is on my list for the 113s. But there are mods that make these cars run far better than original. One is conversion to electronic ignition and in my opinion, a 3:27 rear diff. I am not alone on this and was apprehensive of both changes. But I have to say, the rear was a welcomed change. The ignition goes without saying. I am not inexperienced or new to these cars or the design engineering. My mods are for my stye of driving and the running gear/engine take it quite well. If one likes the high rpm/speed performance of the original gearing, leave it be. But, if not, there is the 3:27 readily available option. I own all models of the 113 and a 190SL. Have so for over 35 years. I have converted all to electronic ignition, and one has been geared to 3:27. [67 standard 4 speed ,250-Euro].

Be advised that this swap out may not be as basic as one may think. I'm just about done changing to 3.27 gearing and decided that changing the entire swing axle assembly (from a 280SE) was a better option than trying to install a differential. The job entailed different emergency brake cable and disassembly and reassembly of the rear disc braking system and, if you want an accurate speedo, a new pickup gear. I'll have about 10 hours into the project total.
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