Question about Rear End Housing Construction - Page 2

AusTexKid · 10-04-2008, 12:17 AM

After talking to several local welders about it, it looks like the aluminum to steel welding is out. It would indeed be difficult and expensive to go this way and the chances of success are doubtful. In fact, the most common advice I received was "ditch the 10-bolt and put a 9" Ford in it". That's almost certainly what my final solution will eventually be. But for now I have another idea about reinforcing the 10-bolt housing that I think will be much easier to do. I like Topspin's idea about building a brace but I'm not going to spend that much effort on the housing only to break an axle or the diff. unit next.

So here's my current idea. It's possible that my problem is just a defective weld from the factory anyway. Only some of the fill material has broken out of 1 pin weld. The other 2 pins and the axle tube have not moved. I've now seen the video of Double-L running 11.60's on the same 10-bolt so I know it's possible to do it. But just to add some insurance while I have the rear end out repairing the bad weld here's what I'm thinking. All I'm trying to do is prevent the axle tube from rotating in the aluminum housing. If I weld a piece of aluminum to the aluminum housing and a piece of steel to the steel tube they can press against each other to prevent rotation without actually being joined. And it eliminates the whole aluminum to steel welding problem. Put about 3 of these on each axle tube and it should do the trick. Then I'll just keep an eye on it. Sometimes the simple ideas are the best.

Topspin · 10-04-2008, 10:53 AM

To take your idea in a little different direction, you could make a pair of semi-circle plates, one of each material, mount them perpendicular to the tubes but next to each other, them bolt them together. If you clamp them together before welding they would remain close enough together to bolt up solidly. One would be on the housing and one on the tube. Heck, I guess you could just bolt them together first with a good 2 part epoxy between the plates even. You're right though, the full brace would be much more involved.

tnssrman · 10-04-2008, 11:50 AM

Be Careful When Welding Aluminum!!! The Heat Up Process During Welding Can Reduce The "heat Treat" Of The Aluminum. It Could Also Hurt The Interference Fit Of The Tubes In The Housing. You May Just Make Things Worse!!!!! The Area Around The Weld Will Be Soft,no "heat Treat".

Topspin · 10-04-2008, 05:51 PM

I'm with you tnssrman, welding on that housing would scare me.

xoxoxoBruce · 10-06-2008, 10:36 AM

Wait until the SOB breaks... it may not.

Greg Ducato · 10-07-2008, 06:27 AM

Depending on how far the axle tubes extend into the housing, couldn't you just drill and tap through the housing and axle tube and run a bolt through both to retain the tube and keep it from spinning? It would be cheap, easy and get the job done. Use red loctite to seal and retain the bolt.

AusTexKid · 10-08-2008, 02:40 AM

Here's an interesting development,

While working under the truck today preparing to pull the rear end I saw what looked like surface rust on one of the retaining pins. That got me thinking so I got a magnet and checked it out. Turns out the pins are STEEL and are factory welded to the aluminum housing. The fill material seems to be a combination of steel and aluminum. It attracts the magnet, but only about half as much as the steel pin itself. So this brings me back to my original questions about how the housing is constructed. What welding process did the factory use? And was the entire housing heat treated AFTER the welding was done? Given the differing expansion rates of steel and aluminum, I doubt it was. This leads me to believe that a limited amount of welding might be OK. But I'm holding off on pulling the rear end for now until I find someone to do the welding. At the very least though, I'd like to repair the damaged weld.

Greg, I really like your idea for a bolt-on type solution. But given the relative thinness and weakness of the aluminum in that area I think I would need to have a nut on the bolt and not rely on tapping the aluminum. This may be possible as the tubes are fairly large and the axle inside is not. I'll take a look at the clearance after I pull the rear cover. With the axles removed there should be enough room to work on it.

Keep those suggestions coming. You guys have already come up with some good possibilities that I hadn't thought of. And where are all you GM guys? Come on, help a brother out.......

2005SSR6Speed · 10-08-2008, 08:16 AM

Quote:

Originally Posted by AusTexKid

Here's an interesting development,

While working under the truck today preparing to pull the rear end I saw what looked like surface rust on one of the retaining pins. That got me thinking so I got a magnet and checked it out. Turns out the pins are STEEL and are factory welded to the aluminum housing. The fill material seems to be a combination of steel and aluminum. It attracts the magnet, but only about half as much as the steel pin itself. So this brings me back to my original questions about how the housing is constructed. What welding process did the factory use? And was the entire housing heat treated AFTER the welding was done? Given the differing expansion rates of steel and aluminum, I doubt it was. This leads me to believe that a limited amount of welding might be OK. But I'm holding off on pulling the rear end for now until I find someone to do the welding. At the very least though, I'd like to repair the damaged weld.

Greg, I really like your idea for a bolt-on type solution. But given the relative thinness and weakness of the aluminum in that area I think I would need to have a nut on the bolt and not rely on tapping the aluminum. This may be possible as the tubes are fairly large and the axle inside is not. I'll take a look at the clearance after I pull the rear cover. With the axles removed there should be enough room to work on it.

Keep those suggestions coming. You guys have already come up with some good possibilities that I hadn't thought of. And where are all you GM guys? Come on, help a brother out.......

With the Halibrand rear axles they used Magnesium or Aluminum center section and side bells. They would heat up the side bells so they would expand. Then they would put the cold steel interference fit axle tubes into the side bells for the center section. The side bells that the axle tubes went into had holes that we would drill through the steel tubes and thread. Then we would install button head screws with sealer into these now threaded holes to ensure the tube was retained in the side bells.

I would drill out the pins, thread the tube and install retaining screws with sealant like the Halibrands.

AusTexKid · 10-11-2008, 12:04 AM

I'm pretty sure that is how this housing was made as well. It just has the 3 retaining pins on each tube to add some strength. I've done some research on aluminum to steel welding and found out it is possible. The methods are all fairly new and very expensive though. Not something you're likely to see outside of a major production facility. Turns out the major problem in the process is the formation of the "intermetallic compounds" that are formed when the 2 metals are combined. Most of the techniques that work do it by minimizing the amount of this material produced during the welding process (i.e. by minimizing the size of the weld pool during welding). These "intermetallic compounds" are very weak and brittle and their presence weakens the weld significantly. The 2 most successful types of welding steel to aluminimum are laser welding and electron beam welding. Both of them are able to produce extremely focused and controlled heat and minimize the amount of base material that gets melted. That's how they minimize formation of the "bad" compounds.

All this is just the long way of saying that this is NOT what was done on the rear end housing by AAM (American Axle & Manufacturing - GM's supplier of the complete rear end assembly). The steel pin is attached to the aluminum housing all right but there is a LOT of fill material at the connection. Way to much to have been produced by any decent welding process. Which means it has to be something else. Most likely it is a high temperature braze. Probably something like the process described in this link:

Corus Automotive - Corus develops new steel to aluminium welding technique

Which means it is probably possible to repair the factory connection if I can get the correct fill rod. This may be difficult too but I'll find something. Maybe the Super Alloy 5 rod from these folks would work. Have any of you used it?

Brazing Rod

In any case I'll still need to add some reinforcement so I'm also looking at doing what Joe and Greg have suggested and using a bolted connection as well. Between the factory pins and a couple of Grade 8 bolts per tube the housing should stay together long enough to break something else instead.

Here are a couple of pictures of the pin with the missing fill material. The first is from the bottom showing the missing fill. The second is the same pin from the top where the connection is still intact.