Differences between a 750's and 101's (4 speed) spider transmissions

[Tommy_Escuderia]

Hello,

I'm an owner of a Giulietta Spider 750 Spider 1957, and I want to know which differences there are between a 750's and 101's transmissions because in my car has been installed by the old owner a 101 4-speed gearbox, but it produces a lot of vibrations, specially when you pass over 90 km/h. I suppose that the 2 gearboxes have different sizes because the supports had been modified 2 or 3 cm to back, but I'm not sure about it.

Is it possible to install the 101 engine and gearbox into a 750? How?

Thanks a lot, and sorry for my English.

[101 Alfa Mike]

I would describe the usual sounds as gearbox noise and driveshaft vibration.

If its a vibration problem, I suggest you replace the rubber flex joint behind the gearbox. Then, check the alignment between the engine/gearbox and the front driveshaft. It may be necessary to space the transmission support down to reduce angular deflection at the flex joint. Hopefully, that will fix the problem.