I hope they do, My lst diffs that I built a few years ago have been thru a variety of motors inc a 1717 and they feel as smooth as the day I built them.

Ok, i`m doing a new diff now.. The new diff that came, was somewhat tight just as the other one`s been.. When rotating the pinion, i feel every tooth touching..
I can turn it with my fingers easy, but it feels alittlle notchy. No slack, ofcourse.

How tight should this mesh be, when i do my shimming now? Should i shim less tight, so everything runs silk smooth, or is it OK for a new pinion/ring gear to be this tight?

It had one shims on the cup side, none at the ring gear side. And one shim on the pinion. Just as every other LST diff i bought.

I know that the pinion shim is the one that has to go to get it smoooooth, but i`ve read about letting new part be alittle notchy too, so i want some opinions from you guys..

I feel that as long as it is rolling all the way around without catching, it will wear in and become free. If the pinion can make the ring gear do a full revolution and you don't feel any of the teeth suddenly catching like they want to lock up, just the same kind of rubbing all the way around, they will wear into each other and become free rolling. I would however take it easy on the throttle at first as a ''break in'' procedure to give a chance for those teeth to wear into each other.

Sounds fine, I like the diffs to feel like that so they wear in and still have a tight tolernace.

Ok, it got tighter when greased and screwed together, so i removed the pinion shim now.. Now i can barely feel some teeth in one short spot on the ring gear, so i guess i`m all set.
Absolutely no slack between pinion/ringgear.

I`ve also shimmed all spyder gears (0.1 on the 4 small, 0.2 on the 2 bevel gears), and they got nice and tight, but still run smooth..

Greased everything everywhere, twice, so i should be done now.
Also made the pinion axle flat where the grub screw is going, and should be able to just set it against the bearing without any shims, and tighten the grub.

Tomorrow i will open my front diff as well, and give it the same treatment, just in case..

I might open the rear diff again after a few packs, and reshim it after it wears in..

If this diff blows up now, i dont know what better to do :)

I found this guide helpful for shimming LST diffs (XXL diffs come with the HD cups installed) : http://hdrcvideos.com/forums/viewtopic.php?f=18&t=15378

I`ve been through that one the first time i did the LST conversion.. :)

But its a great thread!