While wandering through a junkyard a few weeks ago I stumbled upon a 6-lug, 9.5 inch, 14-bolt semi-floating rear axle. Hmm, it's got a 3.73 gear set, just like the weak-a$$ 10-bolt under our '94 1/2-ton Suburban, so it should be an easy upgrade! /forums/images/graemlins/thumb.gif (And it was an easy bolt in. The pinion yokes even interchange so that you can still use the stock U-joints).
Anyway, the nuts on the U-bolts were pretty rusted, so I just cut the U-bolts off. I was pretty amazed to find that the ends of ALL of the U-bolts were nearly rusted in two! /forums/images/graemlins/yikes.gif You can't see it because of the way that GM installed the rear end under these trucks, but the inverted U-bolt design is seriously flawed. The stamped plate that goes on the bottom of the axle does not have any drain holes. So any water, mud, salt, etc. that gets splashed into the open top of the plate is trapped there forever. This stuff builds up until it is flush with the top of the plate. But it is also packed in around the last 1-1.5 inches of the ends of the U-bolts. This slowly eats away at the unplated bolts. The truck I got the axle from was a 1990 and the U-bolts were MORE than half gone. On our '94 Sub (which has spent its entire life in dry, salt-free Colorado) the U-bolts were slightly less than half gone. So you folks that live in wetter climates, and especially those of you that live where the roads are heavily salted, should check with your local GM dealer ASAP about ordering up some new U-bolts, before you hit a bump and get a big surprise! /forums/images/graemlins/yikes.gif /forums/images/graemlins/blush.gif
The good news is that GM seems to already know that this is an issue, since they only charge $1.70 each for new bolts. I also ordered up a new set of rust-free attachment plates. If they don't come with drain holes in them, you can bet that I'm drill some before I install the new plates. /forums/images/graemlins/whistling.gif
Anyway, the nuts on the U-bolts were pretty rusted, so I just cut the U-bolts off. I was pretty amazed to find that the ends of ALL of the U-bolts were nearly rusted in two! /forums/images/graemlins/yikes.gif You can't see it because of the way that GM installed the rear end under these trucks, but the inverted U-bolt design is seriously flawed. The stamped plate that goes on the bottom of the axle does not have any drain holes. So any water, mud, salt, etc. that gets splashed into the open top of the plate is trapped there forever. This stuff builds up until it is flush with the top of the plate. But it is also packed in around the last 1-1.5 inches of the ends of the U-bolts. This slowly eats away at the unplated bolts. The truck I got the axle from was a 1990 and the U-bolts were MORE than half gone. On our '94 Sub (which has spent its entire life in dry, salt-free Colorado) the U-bolts were slightly less than half gone. So you folks that live in wetter climates, and especially those of you that live where the roads are heavily salted, should check with your local GM dealer ASAP about ordering up some new U-bolts, before you hit a bump and get a big surprise! /forums/images/graemlins/yikes.gif /forums/images/graemlins/blush.gif
The good news is that GM seems to already know that this is an issue, since they only charge $1.70 each for new bolts. I also ordered up a new set of rust-free attachment plates. If they don't come with drain holes in them, you can bet that I'm drill some before I install the new plates. /forums/images/graemlins/whistling.gif
