Take the speedo drive gear out of your old box and see if it fits into the new box.

My guess is the transmission.
Same thing happened to me. I found that the output shaft on the 5spd has something like 6 teeth and the 4spd has 7. These are the teeth that are machined as part of the output shaft (= can't replace).

Are you sure you didn't hit the end of the speedo so hard that you bent the needle???

my guess is speedo drive gear is wrong for the 4.11 diff like the other guy said you may need another drive gear

umm 4.11, 14/185/60r, wasnt much difference with the old a12, but since upgrade to a14 and 5speed 60a, the speedo has gone out heaps

are the diff gears 4.11 ute gears or 3.8,3.9 B'bird gears also what whl/tyre set is on the car.

cheers

you also forgot your new wheels...

goto the transmission shop and tell them how much it's out and give them the cog off the end of your speedo drive cable.
They will give you one to rectify it, if it ain't right then you can always get another one. Mine cost $5 for a new cog.
Cheers
Damo

my a14 is in with, 5speed (60a) and h165 diff, but my speedo is out alot at 92km i am actually doing 80km...... what do i do to rectify this and why is it out so much ? cheers