Tuesday, 6 October 2009

What a 'differential' a day makes...

Having spend most of Friday looking for parts, Saturday was a day out of the garage. On Sunday afternoon, I decided to tackle the differential as I couldn't make any headway on the gearbox.

The diff is a big lump of metal used to direct drive from the propshaft (which runs parallel to the car in the transmission tunnel) through 90 degrees to the rear wheels. A point to note here is how essential it is to place the propshaft in the transmission tunnel before the diff gets fitted - if not, you have to remove the diff again.

Once we (my wife helped with this) had done all the lifting, measuring and general fettling to get the diff in place, we tried to line the bottom mounting bolts up. This is where progress ground to a halt for a while. Much head-scratching, swearing and chin-rubbing later and we were no nearer - the distance between the mounting points on the chassis was LESS than the two mounting points on the diff.

A plea went out to the Caterham Motorsport community and they didn't disappoint. Use a narrower bolt to support the diff through the top mounts and the bottom mounts line up. Get the lower bolts in and replace the temporary bolts in the top with the correct long bolt.

Those who feel nervous about gratuitous use of a rubber mallet might want to get someone to help with the next bit as having coated the top bolt with copper slip, it needs to be soundly walloped to get it through the diff. After 10-15 mins of smacking it (good for the aggression relief), the bolt was through and I could get the nut on as necessary. Except, I'd forgotten to put the washer under the bolt head which was 11 inches, two chassis mounts, two diff mounts and about 15 washers away! I was not amused...

Anyway - after all that, the diff's fitted. But not before I had to remove it for a third time to make sure the washers were fitted the right way round. In places, they're chamfered and the chamfer has to be towards the rubber mount where appropriate.

So I can now choose to press on with the gearbox/bell-housing/engine fit or continue with the rear suspension.

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