POSI vs SPOOL

[Dwight Southerland]

Originally Posted by Billy Nees

Ahh, the age old question, the spool for less rotating mass or the posi for less frictional losses. I'd love to see someone do a "back to back" test on them at the track. It's kind of hard to do with a GM rear.

We did it twice years ago and concluded that the posi was a bit faster, but no quicker.

When I first put my '67 Z28 together in 1980, I tried to run the posi and spent way too much time and $$ trying to make it live. Lot's of dollars to Tom's Differentials and heat treating facilities. Worth about 15 runs before something would break. Building your own is necessary to insure the clutches work correctly.

The best approach would be what Jeff says. Rifle-drilled or small diameter axles, aluminum spool, micro-ed gears, loose bearings, light wheels and tires. MHO