Differential Change.

Differential ratio and overhaul.

Just a quick update. Whilst I had the transmission tunnel out and the prop shaft disconnected I decided that it was time to change to diff ratio to something more suited to a V8.

Getting the diff out was relatively easy, just a case of undoing the chassis mounting bolts & CV joints and letting the diff drop out (they are ^*@£!>% heavy!)

I took the diff to Road and Race Transmissions near Sevenoaks, Kent. They specialise in diffs and gearboxes for clubman race cars etc (they supply recon gearboxes and diffs to the Caterham factory).

Contact Info: Road & Race Transmissions, 01959 525105. Filston Farm, Sevenoaks, TN14 5JU.

The rather rare 3.14:1 ratio was available at £300 and reconditioning the rest of the diff & fitting the ratio added another £150 to the bill. R&R can do the work in a day if you're in a hurry but would prefer to slot the work in when they have a gap. I cannot recommend their service highly enough.

During the ratio change, it became apparent that the ratio that I'd been using for the last 3 years was not a standard 3.62:1 LSD but an unusual 3.9:1 LSD used in some odd GLS/X Sierra variants. This would explain the somewhat frenetic nature of driving my Rush on the motorways.

Getting the diff back in was more problematic as I was fighting gravity this time. The following pictures show how I resolved the problem!

There was a rather complicated process of jacking the car up to compress the rear suspension so that the de-dion bar was at its most rearward to get the diff back in (remember it swings about two trailing arms). Once the diff was in the void, the de-dion bar was then allowed to drop to let the diff then rotate into the correct position. The rest of the operation was then straight forward.

Driving the car.

Payment of a year's insurance and tax saw me back on the road at the end of January. The new engine and rear end made the whole driving experience somewhat nerve racking. The roads were cold and damp and any attempt to get the power down was met by wheel spin and the back-end trying to overtake the front. The driveability at mid-range was far more comfortable and I found myself having trouble staying the correct side of any speed limit. In fact, it's now almost impossible to use fifth gear and drive at under 30MPH (as was the case with the old rear end) without the fear of stalling.

In fifth gear: 40 MPH @ 1500 rpm or put it another way 80 MPH @ 3000 rpm.

I'll update my speed v ratios page once I have a full set of information.

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