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Frankenbox

Posted: Sun Aug 02, 2026 6:51 pm
by kerbz
Hello all, just wanted to know if anyone's running one of these gearboxes and what their opinions on them are. I have a series 2 and would like to maintain the original look inside with the long stick. But want to run a 1098. I know the place in Derby can do them but does anyone know what's involved. Is it do-able at home. TIA.

Re: Frankenbox

Posted: Mon Aug 03, 2026 6:02 pm
by myoldjalopy
Its do-able, but not straightforward, if you want to keep the original gearstick, transmission tunnel and handbrake.
Worth taking a look through this thread: viewtopic.php?p=648663&hilit=803cc+engine+swap#p648663
Its much easier to do what you want with the 948cc engine/box upgrade.....

Re: Frankenbox

Posted: Tue Aug 04, 2026 10:38 pm
by kerbz
Thanks will do

Re: Frankenbox

Posted: Wed Aug 05, 2026 9:18 am
by myoldjalopy
Yes, the 948cc engine/gearbox conversion is much easier to do, using the 948 gearbox without the remote shift attachment.The main thing to remember is to swap over the reverse gear selector from the 803 box and thus retain the 803 reverse gear selection mechanism, which will reduce the risk of selecting reverse when attempting to select fourth gear. You may wish to swap the diff as well but its not essential.

Re: Frankenbox

Posted: Wed Aug 05, 2026 11:16 am
by geoberni
My SII had his 803 gearbox fitted with 948 internals when he was rebuilt in 2003, unfortunately the person(s) doing the rebuild couldn't tell the difference between a 948 and a 1098, so he got given a mismatch of engine and clutch, which took me a few months to realise when I brought him :roll: :oops:
So it's perfectly feasible.

Re: Frankenbox

Posted: Wed Aug 05, 2026 2:01 pm
by myoldjalopy
As I said, the 803/1098 conversion is do-able, but not easy if you want to retain the originality of the interior. To do that, you have to follow all the instructions I put in the thread linked above. That's a lot of engineering work.
But if you don't care about keeping the originality of the old gear lever, transmission tunnel and carpet, then the floor will have to chopped. The handbrake lever will need to be moved back, or replaced by the later type. Then there's the fun of the speedo over-reading, unless it is recalibrated.
In contrast, it is much easier to do a 803/948 swap, whilst keeping the interior original.