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Posted: Wed Jan 14, 2004 8:54 am
by Peetee
Wheel size and tyre size is as important as the choice of diffs. You need to look at what wheels and tyres are available and make that choice, then work out the diff you need to give a suitable gearing ratio.
Posted: Wed Jan 14, 2004 10:00 am
by rayofleamington
What is the local traffic speed? The 3.9 diff would be useful for UK motorways (70mph), but if you're not going to go above 60mph then you may not get any benefit from it and the 4.22 Diff will give better acceleration.
As mentioned - tyre size is also important, as 13" wheels will lower the gearing.
Posted: Wed Jan 14, 2004 1:39 pm
by rayofleamington
That's probably a good option.
don't be too hard on the gearbox though! The‚smooth case box (for the 948 engine) isn't really up to the job so hard take-ups and hard gearchanges should be avoided.
I'd recommend to keep an eye out for a Midget 1275 gearbox, which visually similar to the ribbed-case Minor 1098 box, however the midget box it is a bit better.
The other option is to go for a Ford 5 speed box (or similar) - I don't remember seeing (manual-gearboxed) Ford Sierra's in the US but maybe there is an equivalent.