I have a 1981 500SLC I would like to put a 5-speed (manual) trans in the car ….any suggestions.

John Olson replies:

My suggestions? Forget about it! The improvement would be minimal for a whole lota’ cost and monkey business. Gertrag made (may still make) a strong five speed manual box that AMG offered during the 1980s… priced at $14,000 then! I still have their little price book that listed about 50 options with prices…  that being one. The “cheapest way to do it would be buy a1983 – 1986 Euro 500SL with one of these manual five speeds as a donor car, swap out what you want and sell the donor.

On the down side, you will dilute the long term appreciation of a rare car; substancial if it is a nice car. I consider the 500SLC to be the most significant collectible Mercedes-Benz of that decade… the decade of the 1970s… even though your car is an ’81. You already have the four speed automatic, which in itself enhances that car’s value.

I have done transmission and gear-ratio and rear axle ratio transplants on a number of cars for racing & rally purposes, and assure you the benefits gear changes are elusive and application specific. Every choice is a compromise. Street or track use, under or over 100 miles per hour driving, stock weight or lightened? The 500SLC, as one of the few homologated rally race cars Mercedes-Benz ever sold to the public, is a very hard car to improve upon. Only 2,769 were built and less have been found 50 in the USA. It is the lowest series production car built by Mercedes- Benz in that decade. My suggestion: keep it original.

Many of the SL Mercedes-Benz questions are answered in our SL Market Letter, published about 12 times per year. For a nominal subscription fee, you can have SL Mercedes price trends and exclusive SL articles written by author, John R. Olson – publisher of the SL Experience book. You can subscribe to the  SL Market Letter here.

Q: My 230SL needs a new interior. The original cognac color is attractive but all the replacement cognac materials that I have seen do not match the original cognac color and they are also not very attractive. In your opinion do I hurt the value of my 230SL if I change the interior vinyl color from cognac as on my vehicles data card to something like bamboo or tan? Please advise your thoughts. Thank you.
Best, Steve

A: Short answer: Unless the car is too original already, go ahead and change the interior color.

Long answer: There has always been a “romantic notion” that preserving a car’s original color and equipment make it more valuable. In the real world it is only true for cars in good-enough original condition, overall, to be eligible for the newly emerging “Heritage Class” of cars at prominent Concours d’Elegance (different labels for different shows). A car can easily fall out of eligibility for that distinction, when only one component, such as interior, or paint get bad enough that they would only be placed in, but never win even a third place in this category. A a well executed interior or exterior color change, will not hurt, and may well help the value of most collectible cars. By “well executed” I mean a correct paint color or upholstery material for the year the car was built and well enough executed that it impresses the judges at a car show. In this same vane, adding authentic period options, such as an up-graded radio the was in fact available through the original manufacturer that year… is never faulted if I am chief judge. Each concours has it’s own rules of course, and sometime it extends to allowing after-market options if they are correct to that time period… such as metal, exterior sun visors common to cars of the 1940s and 1950s.

Many a trophy winning car (75% in one survey I did a few years ago) has had a color change, or even an engine replacement. As long as it is correct for the model and year in question AND the especially when earns car show awards, it will not hurt value. Preparing a car for judging is not for everyone but if a Condition 1 level valuation is sought show-judging bring a “third party” (not the owner and not the restorer) measure of workmanship and authenticity lined up along side other cars vying for the same distinction. For me, even a fresh “total” restoration does not earn Condition 1 status until it has been so judged by third party judges.

Reply by Olson ….
 
No, a 1980s transmission is not a "natural" implant. Bell housing would require significant change, length of trans. is different — requiring custom spacers, and worst, it is a "side shifter" — the control levers do not come out of the top of the box as on the 113 manual transmissions…. this means more improvisation and odd location for the lever coming out of the tunnel.
 
The correct 5 speed manual transmission for your "Pagoda SL" (and most other 1960s Mercedes-Benz) is a "top shifter". The smartest way to acquire one is actually buying a 230SL with a 5 speed box (the most plentiful source), swap all the parts and sell the donor car. That is because buying a transmission is only the beginning. Drive shaft is different. If you're changing from an automatic the fly wheel and ring gear is different. Also you can know it shifts OK and is quiet before you buy it if you can drive the car. BUT… see next paragraph.  
 
The whole project is unnecessary as changing the rear axle/differential (rear-end gearing) is infinitely easier. I now favor changing rare axle ratios to finding a five speed, for 1960s Mercedes-Benz. 280SEL 3.5 or 4.5 sedan parts offers soe nice ratios. Identical measurements. Everything fits. Your 280SL probably has a 4:08:1 rear ratio. That's OK if you live on Pikes Peak. For anything else there are three sedan rear ends (good: 3.69:1, better: 3:46:1, and best: 3.27:1) that will move fourth gear into overdrive with quieter highway cruising. There's only minor reduction in low speed performance. First gear is already so low that it can accept a longer legged (lower numerically) rear end ratio. I did this with my 300SE (six cylinder) sedan; installed a 3.27:1 differential from a 280SEL 4.5… and I love it. MGP climbed 15% too.

280SEL 4.5 sedan differentials with either 2.24 or 2.27:1 ratios are lurking in many Mercedes recycling yards. You'll want to replace the axle bearings on principle, but for a small fraction of the cost of a new differential, you'll probably be as happy with the results as I am.