Was at York Raceway (UK) over the weekend and axle problems developed. When doing a burnout passenger side wheel spun up, however drivers side stayed still. This happened a couple of times but has never happened before.
Was advised that the problem was to do with the Suregrip unit.
Since then we have removed the diff to investigate further and done a fair bit of research into the subject. Some people say that unit is not repairable but others say they have 'machined' the cones and added shims to restore its performance. However, they do not go into great detail about this process. Exactly what needs machining and by how much and where do the shims go? Does anyone know where I can get hold of some of these shims?
As cash is tight I would like to try and repair the unit but if push came to shove what would anyone suggest as a good replacement and supplier for this unit.
Diff has a 489 casing with a suregrip 'cone' type arrangement.
I have linked some pics of Suregrip in pieces, showing inside of cones and backside of gears. Both sides show wear/friction burns. Is this normal wear?

Pics

Thanks in advance for any assistance.  

time for a spool,and better axles  

Or check into a Detroit Locker, we ran a Detroit True-trac for years in an 11 second street/strip B-body with no issues.

If you race regularly though, go with the spool and aftermarket axles for sure.

Even if a cone-style Sure-Grip is working perfectly, it won't hold up to serious power at the drag strip for very long.  

Clutch type 8 3/4 pos. units are superior in strength to the cone type units. They are rebuildable and the clutchs are available from Mancini racing.  

Have the cones cut about .030" on the bottom as long as there are still groves in the sides this will work.  The cones wear and bottom out.  If you can find a friend with a lathe as I did, your all set.  I did two of my rears and they both work fine.
Don  

Your right the cones work fine on a street car, don't bolt on a set of slicks though, I got 2 weekeneds on a new cone unit and then installed a rebuilt clutch unit 10 yrs. ago, haven't had a problem since.