Hi all,
I'm new to this site but figured from the other responses that I might get a helpful answer.

I'm in the process of restoring my XK120 and am deciding about gearboxes.

A big part of me wants to keep the feel of the original box. It's part of the character of the car! But I also don't like the idea of running around in 4th gear the whole time.

How easy is it to fit an external overdrive unit to the 120 without modifying the chassis? i.e. could I fit a 140 gearbox overdrive onto the 120 gearbox without too much trouble or does it simply not fit with the chassis cross member in the way?

Thanks in advance for any help/advice!

 

I really don't think you will have room without doing a lot of mods. Unless you want to idle at 70 mph, the car was made to run 120 mph in 4th. Then the sound of the car would be way off.

 

Thanks Jagfixer, I was worried you might say that...

I'm not worried about the ratios at all, as (basically) all 4th gears are direct drive (1:1), sticking an extra ratio at the end will just make cruising calmer like in later cars.

 

There are some shops that actually sell Toyota Manual 5-speed conversions to the Jags. There used to be one here in Tennessee, but have not seen and ad for a while. Check local custom shops for conversions. Flywheel, clutch, bell hosing adaptors, and tranny. Probably will need driveshaft modified. You don't need to listen to the naysayers, your car, make it like you want. Just keep original parts. Good Luck!