I need educating in diffs

[Ads7]

Just stripped my noisy diff out of the 7. Surprisingly easy but awkward job. 

Anyway!! I would like to know more about them. I'm sure I have a ZF LSD in the standard Sierra casing. What I'd like to know is what is meant by the ramp angle and to help me understand what would the suggested ramp angle be for my diff.

1800k 170bhp

Adam

[Mankee]

Angus' website will help you ID the sort of LSD you have:

http://www.mycaterham.com/66828/117416.html

Google (or Jonathan Kay) will help you with ramp angles, e.g.:

http://www.intothered.dk/simracing/differential.html

You also need to consider the preload. I too have a ZF, but it has a ridiculously high preload of 75lbft. For a light car like a Caterham it should be something like a max of 30lbft. I plan on pulling the diff out to give to someone to get the ramp angles and preload sorted, as my car can have a tendency to push on at the front, not helped by either of these tweakable features.

[Ads7]

Thanks Mankee. So how can you find out the pre-load of a diff? and how are the pre loads and ramp angles set once the diff apart?

thanks

Adam

[Mankee]

You say that you've already removed the diff, which makes measuring the preload a little/a lot trickier. You would need a dummy driveshaft or two with splines to hold one output against the other.

With the diff still in the car, you can remove a wheel, leaving the other on the ground, and use a torque wrench to measure when you can turn one wheel independently of the other that's one the ground. This is the preload and is how I measured mine.

I've not looked into it too deeply yet, but I would assume that you can shim the diff casing (not the outer casing, but the diff itself) to alter the initial clamping force and adjust the preload. Ramp angles would need to be changed by swapping/modifying the cups inside the diff. I'm sure one of the plate diff manufacturers, possibly Tran-X, used to have multiple sets of ramp angles machined one the cups so that you could chop and change to suit the application without having to buy complete new cups.