Diff

[AndrewT]

I know it's been talked about many times but the 3.9 ratio seem to be fetching big money however my s2 has a 1098 with 948 box and long gear stick,I haven't checked my ratio as yet but at 50mph the engine is rather high revving which I'm not comfortable with so:

I have a couple of 1098 and 948 gearboxes which I plan on coupling up to create a 1098 long gearstick box
So I have been offered a 4.22 diff and casing for £100 ad apparently it was bought as a recon unit(pinch of salt)

What's everyone's thoughts on ratio and price?

[philthehill]

With the 1098cc engine you should be using the 4.22 diff.
If the diff offered has been reconditioned it is well worth £100.

[liammonty]

If the diff in your car is the original ratio, it will be 5.375:1 which is horribly undergeared for a 1098. The standard ratio for a 1098-engined car was 4.22:1 and it's pretty well suited and will be a huge improvement on the original Series II ratio if that's what you have currently.

I fitted a 3.9:1 diff from a Midget to my 1098 Traveller a few years ago (the car had a strong engine) and I thought it suited the car well, but it's at the limit of what would be suited to a standard 1098. The 4.22:1 will be fine, and as you've discovered, a few hundred pounds cheaper than a 3.9:1!

Good luck with the 1098 'box conversion. I fitted an old SII car I had with a 948 'box that I adapted to take the long gearstick and it worked well, but that was behind a 948 replacement engine. Converting the 1098 'box is more of a faff and requires some machining but there's information on the web (and I think on this forum) of how to do it. Nice to hear you're keeping the long gear lever rather than changing the floor panel!

[myoldjalopy]

'liammonty' is correct that converting the 1098 box to retain the long stick gearlever is, as he puts it, 'a bit of a faff'. It would be easier to get a 948 engine and retain the 948 gearbox, which you suggest has already been converted to retain the long stick. The 948 engine is generally considered to be a 'smoother' engine than the 1098.
I have the 948 engine/948 gearbox conversion in my SII and its absolutely fine.

[philthehill]

What ever BMC/BL gearbox you fit it will still have the same top gear ratio 1 - 1.
I would suggest that you just change the diff and forget about everything else.