I had to hunt down my 'Fact Book' to check out the BE info from McNeish. I'd read that before, but quickly since it doesn't relate to my car. It seems that the predominant difference in the BE posi unit was the larger (and fewer) teeth in the spider/axle gear set, with the same posi clutches, but with different posi springs with slightly higher spring pressure (75 vs 50 psi). I suspect that in turns, the BE rear makes a bit more noise in the rear than the standard rear, due to the fewer number of spider teeth, has that been noted previously? In reading that section again, I noted a small error in Jerry's book, when he says the change in the differential housing from the .3894860NF to the 3989341NF pn occurred in September'69. The differential in my mid Sept '69 Z28 has the 341 housing assembly dated '0829', so that change occurred earlier than stated.
Is the BE (4.10 gear set) the only such COPO differential? The differential section in Jerry's book also states there were higher numbered gear sets (4.56 nd .488) available in 1969 via COPO/9511, but the implication is that these rears had the standard Posi setup, since the BE was the only one singled out for the larger spider/axle gear differences??
Note: I just checked my Hooper book *69 Camaro Reference Book*, and on page 362 he lists the DT rear (4.56) with a similar note (with heat treared ring and pinion and spider gears), but notes the DT as being for COPO 9560/9561 HD, and the BE for COPO ZL-1 HD. Is all of this information accurate?