Posted by Charlie on Saturday, December 23, 2000 at 06:19:32:
In Reply to: rear axles posted by hank on Saturday, December 23, 2000 at 04:55:25:
You almost certainly have a full floater (FF). A FF has a hub sticking out about 3-6" and it's about 4.5" diameter and has the flange of the axle shaft attached. The axle flange is bolted to a hub which is attached to a spindle sticking out of the axle housing with two tapered roller bearings just like the front axle.
A semi floater (SF) has the lug studs sticking out of the (bigger) flange at the end of the axle shaft. It rides on a single usually straight roller bearing. there's a variety of axle retention mechanisms for SF, the most common and notorious is the C clip inside the diff.
With a SF if the axle shaft breaks you lose the outer half of the axle and the wheel and tire - catastrophe. The axle shaft carries torque and part of the wheel load.
With a FF if the shaft breaks nothing acute happens at all. the shaft only bears torque, no load. And the axle shaft can be pulled out with the wheel on the ground and the diff buttoned up. And because of the lack of a C clip some better traction adding diffs can be used, like Detroit Locker/NoSpin, though they recently came out with a C-Locker.
Most likely a late 70s W200 came with a FF Dana 60, though it's possible it has a SF60. Some "light 3/4 tons" and 3/4 ton vans have come with 8-lug SF Dana 60s and 8-lug SF GM 14 bolts and Ford 10.25" Sterling axles. Chrysler never had a proprietary full floater after our venerable M37/Power Wagon 9.625", which in some ways is as strong as a Dana 60. The 60 has a 9.75" ring gear, about 4% stronger; but only two pinion bearings as opposed to three. The minimum diameter of early coarse spine Dana 60 axles was as narrow as 1.31", whereas the 9.625" diff necks the axles down to 1.25", 14% weaker. The 1.25" shaft is 42% weaker than a nice fat 1.50" shaft, standard on late Dana 60s (fine spline shafts), all Dana 70s and 80s, Ford 10.25" and GM 14 bolts.
Charlie
PS: The shear strength of an axle shaft, inother words the torque it takes to twist it off, metal being the same, is proportional to the cube of the diameter.