Since the 'Birds I have been running the same diffs w/o a rebuild. IRS diffs, the newer blue ones (not gold) cut for the "D" diff drive ring. Stock, mod, 19t, whatever i toss at em they have performed flawlessly on a single build. Still glass smooth. The plastic outdrives are a lighter advantage for stock class, but the durability of the IRS outdrives cant be matched, for a few grams more. When i am at a bigger event i use the Niftech aluminum dogbones with the SWD swivels for zero outdrive wear. When im at the local track i run the stock plastic dogbones with pincushions... but not in mod. I have bent (twisted) the pincushions in mod. One-way, spool, diff, dont matter. I guess i have been a lucky one to not experience all of the front end damage associated with a spool or a one-way. Its ok, i inevitably glitch when i least need too.
For most, it seems to be from on-throttle tags to the wall. The stress has to go somewhere. Loosening the front diff may be a way, but seems to me its something else. As far as building the diffs, i match the front and rear diff spring in length (after compressing them with pliers per the manual). I then ground the rear diff spring 2 tenths shorter than the front spring. This gives me a "normal" front slightly tighter than the rear diff adjustment, when both are tightened completely, and equally backed off half a turn. Its a great starting point, and i rarely have to do much adjustment afterwards. Having the front diff slightly tighter gives that off the corner-on throttle steering you need in 19t and mod. A spool (a one-way too for that matter) creates so much wear on the driveline, and to me, the car drives erratic on anything other than a glass smooth surface. I guess it all comes down to driver preference, and how deep your pockets are for spares. I would rather finish a race in third, than be on the sidelines with a melted diff, broken dogbone, ETC. Besides, you never know if the fools in front of ya will blow the (plastic) rear diff with two laps to go... its your race then! SUCKA!
- DaveW