navigator wrote:fishsticks wrote:The 8.6 is a parts-bin rear axle: Development costs are already mostly paid for by the the full size lineup. The reasoning behind the 8.0 can only be one thing: CAFE standards. There's no way it was cheaper to commission an entirely new axle/differential for use just in the 360s.
.......this is kind of what I was thinking.
I'm also thinking the difference in material cost in the item itself is negligible compared to the research and tooling cost.
I understand if it costs $800k to develop something but yet you save $1 on a million vehicles it makes sense. I also understand that when you save weight you also get better MPG as well. I'm just not sure in these instances there is enough difference to justify the cost.
Looking at GMPartsdirect the EXT rotor (+$20) and caliper mount (+$1) are more expensive(MSRP) but that is if you walk into the dealer to buy it. I don't think the EXT rotor costs $20 more to make.
The caliper mount and rotor for a Silverado are actually cheaper than the one for either TB and I expect the one for the Silverado to be equivalent or even heavier than the one for the EXT.
If they made every TB with the Silverado brakes and 8.6 rear would they be that much heavier or that much more expensive to make? I don't think so.
Don't get me started on our red headed step child of a bolt pattern either....
I know you never improve a product if you don't change it but I think if you have the same engine, xfercase, tranny, rear end, brakes, wheels etc on the Silverado 1500, Tahoe, 1500 Suburburban and Trailblazer(except width differences) you are going to be more efficient in your processing and need less inventory as a dealer to keep spare parts for all the platforms.
All the differential housings for the TB are aluminum (vs. steel for everybody else, for unsprung weight, as well as vehicle weight, I'd guess, since we don't heed the strength), and the lengths are different than the the full size, because we are narrower than them. So basically, the only parts that cross over are the bearings, gears, and carriers, anyway.
The TB was a BIG seller for them, and the bigger of a seller something is, the more it affects your CAFE. The smaller axle has lighter shafts, carrier, and gears. The smaller brakes save weight, but more importantly than that, they get rotating weight closer to the axis of rotation, so they are easier to spin up. The smaler brakes let you run smaller, lighter wheels, and let you up-sell the larger wheels, both lowering your base price and your fuel useage.
Unequal length half shafts contribute pretty heavily to torque steer when you're in 4WD, and you don't want a soccer mom vehicle that's unstable in the snow.
These parts that are smaller are ordered in such high quanity that you don't really lose out on the quanity discount by having a different part, but you do save a few cents each in less material, and much MUCH more importantly, they save you fuel on a big selling vehicle, which allows you to sell more big vehicles without having to lose money by heavily discounting (and losing money on) your little cars, so you can still meet your CAFE.
Mike
