is it possible to shim the gears to tight? i read somewhere that it should be just enough to take the play out of the spider gears when compressing the side gears with a screwdriver between the cross shaft?

 

The spider gears have a Backlash rating just like the ring and pinion. you can go as tight as you think necessary for your application .001 but do remember the tighter you go the fast the clutches wear too. GM and most other companies are very conservative and wanted longevity from there parts. This way they would last and still give you standard performance needed for the street.
It could take a few time to get the shim amount correct as you will only know the exact backlash once the 'S' spring is installed.

Good luck and have fun learning how to make your posi work better for your driving applications. Be reasonable...Too tight and your will totally wreck your posi and getting parts for these unit are not going to be easy. Take care, Jim

JD

 

Actually,you can make the unit last longer,by shimming them tighter,and you can even remove the spring altogether.The majority of the production units are assembled pretty vague these days,so that they are nice & smooth for the soccor mom in the Tahoe.They weren't much better back in the 60's & 70's either.
There were some good articles explaining all of this,back in the late 70's,80's,and a few in the 90's.One of them by Tom,from Tom's differentials.Very informative for those that don't normally do this stuff.Ben Apple was another guy that had some cool insight on this stuff.