Why Choose A Dana 70HD?
I like the Dana 70HD because this thing is BIG! The 70HD is stronger than other Dana 70's for several reasons, the housing uses 4" axle tubes, as well as, a larger center section with heavier webbing. The ring gear is still 10.54" like other 70's but the pinion gear shaft is thicker (stronger) using a bigger inner bearing. The carrier is a little beefier and uses the same bearings as a Dana 80 (much bigger than other 70's)! ALL 70's are great but if I've got to spend a lot to build it, I might as well get my monies worth!
The 70HD only comes in older Chevy duallies (primarily 73 thru 87, and some 88 thru 91 trucks)or motorhomes. Because it's applications always have dual rear wheels, the housing is quite a bit wider than a single rear wheel axle. It also originally comes with 13"x3.5" drum brakes (except for some motorhome applications).
Because the axle is so wide, I had the housing narrowed - OUTBOARD of the brake backing plate flanges - 2 1/2" per side. This will make it the same width as the front Dana 60.
Right now I'll be using 5.86 gears, but after seeing a friend do it, I've really got the itch for 7.17's! I lucked up and found a spool for it so I don't have to suffer through the price of a locker. I'll be ordering custom length axles (1 1/2", 35 spline) from Moser Engineering in the next couple of weeks.
I Love The BIG Brakes!
I'm using the original 70HD bearing hubs and front Dana 60 rotors, calipers and brackets, and dust shields. The wheel stud holes in the rotors have to be drilled open to accept the bigger 70HD wheel stud.