Gearbox compatability

[jeremy fisher]

I am wanting to change my gearbox in my nova. It has a 1.6 16v (x16xel) from an Astra fitted and I was using an F13 gearbox. I have an F10 and the gearbox that came engine (presumably the origional from the Astra). The F10 won't fit the engine but I want to use the internals. I don't want to use the Astra 'box as it is because it has a 3.55 final drive. Is there any reason why I can't use the F10 internals in the Astra 'box? (I'm not sure what 'box it is as it doesn't have a stamp just lots of numbers) The internals from the Astra 'box won't fit in the F10 casing but the F10 internals seem to fit into the Astra 'box just fine, but will it work.
I hope that makes sense.
Cheers

[mowgli]

right, this gets a touch complicated. when you swap the cluster over, the end gear on the output shaft needs swapping to match the diff.. if you leave the f13 diff in place, which i think will be a 3.74:1 or a 3.94:1, not a 3.55:1 on a 1600, but i could be wrong, then putting a different cluster in won't help you much. now swapping the diff, or fitting an f13cr will dramatically help

look at the output gear on the f13 box, and there will be a circlip. undo that, and with a puller, get the gear off.

[jeremy fisher]

Sorry, I was planning on swapping the diff as well. Should've said. But the astra box with the f10 cluster and diff will work?
Thanks

[mowgli]

yes. all the f10 innards will fit. you can still get an f13cr for reasonable money, and the ratios will be way better.

[tom reid]

I'm guessing you want better acceleration, I have a few diff's/cw&p's that might be of use.