Upgrading a 1966 Pagoda to a 5-Speed

By Jason Burton

The W113 “Pagoda” SL Mercedes made from 1963-1971 are amazing cars. Robust, stylish, reliable and still modern enough to cope with today’s traffic. Some of the most coveted models are those equipped with the ZF 5-speed transmissions. Approximately 883 cars were optioned with this transmission out of a total production of 48,912. Consequently finding one of these cars is difficult and prices for them higher than the 4-speed (manual or automatic) optioned Pagodas. More difficult yet is finding replacement parts for the original ZF gearboxes, which beyond bearings that are generic, the rest of the components are made nearly of unobtanium making refurbishment and repairs extremely expensive.

photo 4The reason why these transmissions are so coveted is simple. At highway speeds a 4-speed W113 turns some serious RPM. The 5-speed brings those revs down, makes the car much more civilized, improves fuel economy, prolongs engine life, and overall simply makes the car all that much more modern and livable. Installing a differential from a W108 sedan with an improved gear ratio helps but the 5-speed makes the car even better. Fortunately there is a solution.

Hi-Line European Automotive Experts in Downers Grove recently walked me through a conversion they just completed on club member Lou Karellas’s 230SL from a 4-speed to a 5-speed (that you CAN get parts for). To start they had to source several components including a BMW Getrag 265/6 5-speed transmission (often a good used is better than a rebuilt). Also needed is the transmission conversion kit which includes a bellhousing adapter, cross member, adapter plate ring along with the appropriate flywheel, pressure plate, and clutch as well as 2 BMW transmission mounts for the replacement cross member and a BMW driveshaft in addition to the standard driveshaft. The transmission conversion kit, while common in Germany, can be challenging to find in the U.S. Hi-Line was able to find a source. While the kit makes install possible it does not make it simple.There is a good amount of customization and engineering required to make everything work well.DSCF0262

The first step is to modify the Getrag transmission case with multiple ears needing to be trimmed off (marked in yellow in the photograph) to provide proper clearance since this transmission was not originally intended to be installed in this application. The cuts need to be very precise to allow the transmission to fit though. Too much trimming will ruin the transmission case. Next the sleeve over the input shaft on the front cover needs to be cut off.DSCF0267

Next up are modifications to the original driveshaft which involved a driveshaft specialist welding the front flange of the BMW driveshaft to the existing MB driveshaft, allowing the front of the original driveshaft to interface with the BMW transmission while retaining the stock rear connection to bolt to the MB differential using the standard MB flex disc. The shift linkage then needs to be customized to retain the original shifter in the cabin. Measurements for trimming need to be extremely precise to achieve correct alignment of the shifter and proper gear selection. Once the delicate modifications are made to the original shift linkage it needs to be welded to the 5-speed’s linkage. Stabilizer rods from the linkage then need two 90 degree tabs made which attach to the Getrag transmission’s case.

DSCF0266Utilizing the original bellhousing, clutch fork, and hydraulics, the transmission will now install without great difficulty. Proper alignment of the adapter plate on the bellhousing can be tricky and needs to be exact or things simply won’t mate together. There is also a need to add two small 3mm spacers to the replacement cross member to properly align the driveshaft angle and prevent the transmission from rubbing on the tunnel.DSCF0265

The last step is modifying the original mechanical speedometer drive. While one could convert to an electronic pickup, retaining the original preserves a bit more originality and is more in keeping with the character of the car.

The final result, in addition to all the benefits mentioned earlier, is a car that originally would turn about 3500RPM at 70MPH now comfortably cruising at 2300RPM.

 

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