So this seems like a good time to start thinking about the sierra parts I need. Up until this point, I've not really been taking in all of the various discussions of the different models and which driveshafts/diffs/hub types I've seen and heard. It's all a bit abstract until you actually start getting hold of some bits.
So, a little confused, I started by making the decisions of what I knew I wanted. It seemed to me that everything flowed from the differential - once that is chosen, it dictates the driveshafts, hubs etc. Differentials for the sierra came in a variety of ratios, and two sizes - the larger 7.5" and smaller 7" types. Opinion seems divided on whether the larger one is necessary, or indeed if it's actually any stronger.
I spent a fair bit of time playing with gearcalc to work out which of the available differential ratios would work best for me. It's ultimately got to be an educated guess, of course, but I've decided on 1:3.62 - this will give a sensible-sounding 62mph in 2nd, and a nice low 3000rpm cruising at 80mph in 6th. Sounds ok on paper, there's only one way to find out for sure...
So with the ratio chosen, the last decision was whether to go for an open or limited-slip diff. A bit of reading of people's experiences convinced me that an LSD was the way to go. So, with the decisions done, it was time to find the parts...
A bit of research showed that both the early 2WD Sierra Cosworth, and all versions of the XR4x4, had the 3.62 LSD. So on to eBay I go, and after missing out on a couple, I won a cosworth LSD.
Only then did I find out that the 2WD Cosworth diff was a special 7.5" model which had extra large (and heavy) driveshafts, and according to Dax, is really overkill for the Rush. Given that the last thing a se7en needs is more weight, I quickly decided that I will sell that one on (it's not actually arrived yet) and go for the smaller XR4x4 one.
Because the front end of the Rush uses 2WD parts, and can't use the bits from a 4x4, it was effectively decided that I would be buying parts rather than getting a whole donor car and stripping it - otherwise I'd need to buy two! Suits me, as I'd have to strip it on the drive (so that it could be picked up after all the suspension was taken off), and December is not the month to be outside struggling with 20 year old suspension bolts.
So I found a chap who could supply all of the bits, and bombed over the pennines to pick them up on saturday. Into the back of the car went:
On the steering column, Dax state that the older type (pre-1987) with the square hazard warning switch is needed, however these are rather rare now. I spoke to them on the phone and was told that actually, the newer type is fine, as they sell an adaptor kit (it's the wiring which is the problem). So I've got a newer, round hazard switch type, which cost considerably less...
That was yesterday. Today I made a start cleaning some of the bits up. Obviously they're rusty as only suspension components can be, so it's down to the drill-mounted wire brush and flap wheels to return them to a nice shiney state. Even the dremmel has made an appearance on a couple of the tighter bits. I must admit, I never had any time for dremels in the past, but I've been pleasantly surprised by how good the little drum sanding attachments are at griding off rust.
I started on the rear hubs. About an hour to go from a filthy rusty lump to something which looks quite reasonable:
There's a fair bit of pitting on the back of the hub (right-hand pictures), but I'm guessing that it was only rough-cast anyway, so wouldn't ever have been totally smooth. I'm going to paint all of the exposed parts anyway, so that will be getting a coat. Next stop, the driveshafts, but I need to by a set of torx bits and a pair of circlip pliars first.