converted s111

can anyone tell me if a 5 speed defender gear box off a 2.5 n/a diesel will fit instead of a standard series3 box i have coverted it to a prima engine with dudleighs conversion

I suppose you will put in the transfer box as well, that will give you permanent FWD. The Series front axle cannot deal with that because it has UJ's not the CV joints of Defenders. It's possible of course but you will have to change most of the drivetrain. plus I think the gearbox mounts are different.
Plus any axle change you've got the suspension to deal with as any later axle is set up for springs not leafers.

cheers looks like i might be leaving the old box in then i just thought it would be nice too have the five speed oh well overdrive will have to do

You wouldn't have to change the axle for a defender type thus having suspension problems either change the whole axle for a 109 stage one front axle which has CVs or it might be possible to change just the ends of the axles for stage one type. You could use a stage one front prop (not sure if the length is the same as a standard, then change the gearbox mounts (might need an adaptor plate for the engine but don't think so) and then get a rear prop made up as the length will be wrong. It is possible but a bit a job.
Sandy

Why not put in an overdrive. or a higher ratio kit in the transfer box . A lot less work.

thanks for info i will look into all ideas and i have an overdrive fitted just a thought i had about a 5 speed box but it sounds like its to much work for me thanks all