whats the pin modification?

No. The AE hub keys the front to the rear 1:1 through the slipper, the exotek hub keys the front to the spur (no slipper) but allows you to slip the rear still to save the rear transmission counter gear.

A small but significant difference. Has better bite forward than anything else (with the potential of the center diff, which I have never tried).

It's not!

(I have all of them.)

I wouldn't just throw in the new shims you need to use the right combination of shims to remove and slack.
When you've removed the diff from the gearbox hold the out drive in on hand and the diff case in another hand and push and pull on the outdrive to feel for slack, it won't be much but that's what you need to remove without making the diff tight.
You might need just the new shims or one old and one new or no small out drive shim and both new shims (1 each side) but after you've put the shims in forget the grease/oil for a sec and put the diff back together checking to see if it's got any slack or is to tight.
Once you are happy it's shimmed enough then stick your fluid in.
I've had to shim both my B4 diffs and my SC10's diffs but as I'm in England and can't call up AE I've been finding my own shims. Most have come from Downhill Mountain bike disc brake shims.

Ok, so this still protects the front gearbox using the slipper where as the exotek doesn't use the slipper and only the belt protects the gearbox from the motor.
Do all 3 pads work together rather than 1 to the front and 2 to the rear?
That's one mod I might like into.

Nobody ever breaks a front idler. The COUPLED slipper is hard on driveline parts be cause it forces all the load to the rear end where the weight transfer is.

Do a search for pin modification, and welcome to last September!

Craig, what did you think of the exotek front clutch? I ordered one to try out. For $11 why not, lol.

No, I know what the pin mod is, I've only just spotted the small one line post that says the AE part is the same as the pin mod. Chill.
I've actually read EVERY page of this thread since the beginning biding my time until the FT kit came out, I had learnt all the things to watch for when building and my truck has no bind and has had no issues since I've had it all down to the helpful hints I've learnt on here.
I've needed to make sure my truck is faultless as the scene and support is a lot smaller over here and obtaining parts could be a lengthy process.
The only thing I've yet to resolve is getting the temps down on my motor and with pinions costing £6.10 a time (nearly $10) it's becoming a little expensive as I'm up to 3 so far and I still think I need a different one.

They are about $10 here also. You can save a little by getting the novak 3 pack combos.

I've not seen the 3 pack before, thank you.
I think I'll get the 12/13/14 pack and sell my 14 & 17 on oOple.
Cheers

Love mine, best mod yet.

Did you lighten the diff oil in the front?

WC,
It looks like they sent me .5mm diff shims.

yup, thats what they sent me. you remove that outer small shim, and use these inside instead of the stock shims.

Are the original shims .2? Reason I ask, is because I doubled them up (I had stripped my gears and replaced everything) and still left the outside shim. Everything seems good right now.

And yes, I limited up travel to prevent it from happening again.