I have a non-turbo 1977 123 series 240D (616912) with manual gear (4-speed) and would like to replace the engine with 300D (617912) engine again with a non-turbo engine.

Could anyone kindly guide me if I have to replace the gearbox and the differential as well?

If I also replace the 4-speed manual gearbox with a 5-speed manual gearbox, do I need to replace the differential as well?

Thanks

Do a search on "Ridge". He has done this and participated in a couple/few postings discussing this.

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Jim

i have done this twice. it is best to start with two cars. in the 300 the radiator, speedo, drive shaft and rear end are different. of course also the exhaust. the clutch may be different. i was told that the 300 flywheel is different but when out i cant see any difference. bell housing is same. shift rods are different but could be shortened i believe easily. the driveshaft is different probably only in length. i started with a 300d euro, '83 and put it all in a 240d us '83. it all worked fine. i could never get the cruise working because the euro linkage is different. one motor shock bracket had to be fabricated. be sure to remove the 240 motor mount in the center of the front crossmember that fits into a pocket in the back of theoil pan.

i also did this with a 76 300d auto into a 240 d auto body, 74 pretty much the same deal, one motor shock bracket to fab. again started with two complete cars. the donor car had major cosmetic issues but a sound drivetrain. the 240 was really nice with a professional rebuilt motor fresh paint detailed motor etc... til my #3 daughter decided to fill up with gasoline and proceed to drive from colombus ohio to lafayette indiana. she made it to richmond, surprisingly, before the pistons started melting to the cylinder walls. the conversion cost less than rebuilding the 24 0 again and anyway the 240 115 body witha auto is dangerously slow. good luck

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.