Manual Trans Swap W123->W115 - PeachParts Mercedes-Benz Forum

reinventthewheel · #1 04-27-2015, 03:30 PM

What differences are there between the 4-speed manual transmission as found in the W123 240D and the W115 240D?
Are there any complications in putting the later model trans into the earlier chassis?

VT220D · #2 04-27-2015, 04:10 PM

If you're replacing a manual transmission the W123 transmission will work.

However, there are two versions. One is the early cast iron type with a removable bell housing. It will bolt in and and work fine. This is true even if the W115 transmission is an earlier notch back type. The later W123 transmission is a one piece aluminum case Getrag transmission. To install that one you'll need to remove the flywheel and swap the engine adapter plate. This is because the Getrag transmission is aligned by dowels rather than a machined recess like the earlier iron one. You will also need the W123 shifter and custom shift rods. They can be made from shortened W123 rods. The W115 speedometer cable will not work with the Getrag and you'll need a late W123 cable. Getrag slave cylinders are different as well but are compatible with the W115 clutch master cyl.

If you're converting from an automatic to a stick the W123 won't be of much help beyond the transmission itself. The pedals, and drive shaft are different. There are little things like grommets, hoses and lines, The automatic drive shaft won't work either. For a conversion I'd source the parts from a W115.

If converting from auto to manual have a machinist match balance the new flywheel to the old flexplate. Flywheel bolts are longer than flexplate bolts. Flywheel bolts can be reused but must be checked for stretch per the manual. When removing a flywheel be sure to mark it relative to the crank to maintain proper engine balance.