After all my casting fun I have had another idea. What if I take a stock normal open diff. Wash out the oil and pack the axle holes tight with sand. Just to insure no leaks pack the whole deal in sand leaving the larger hole up and open. Then melt a full pot of alminum and pour it in the hole till it is full. Let it cool and remove. Wash or blow the sand out of the axle holes an splines and there i would have it. A safe cheap unbreakable spool for my diff. Nothing is going to turn or go anywhere inside. Aluminum is stronger than steel by weight and there would be lots in there and it wont ever come out either. Crazy? Perhaps but I dont think so. Don
Ya lost me,,,nothing is going to turn???I must be missing something.Have heard of welding them.I just cant picture how you idea could work.Mark
I read about this done on old ford banjo diffs with lead for traction on muddy roads or fields. Instead of useing sand why don't you just make a band of steel pipe to fit around the differential and pour it full of aluminum? You would have to block off the inner side of the spider gears so they dont get filled up with the metal. I am not sure that pouring it in with the axles in would be a good idea as it may affect the induction hardening of the axle splines. Sounds like a good idea though.
I guess it might work out ok . The only thing is that it wouldn't work so the only thing lost is the time and material you used . Good luck and let us know how it turned out , good or bad ! Retro Jim
He's talking about removing an open differential carrier from a banjo, packing the ends full of sand (where the splines that the axles use are), packing it into a box of sand, and then filling the center (the diff part of the carrier) with molten aluminum. It would essentially be a "cast in place" mini-spool. Instead of replacing the spider gears, he'd just be locking them up with solidified aluminum (like welding, but without the propensity for breakage). Neat idea. I wonder how much shrinkage you'll get. Might need to preheat the carrier before the pour to make sure you don't get parting lines or cold spots. Aluminum contracts more than steel does as it cools though, so there's still going to be a small size disparity when it's all said and done. Probably won't matter though, since you're no trying to replicate splines so much as lock the spider gears solid. Better be sure you're done with that carrier though, this is one of those mods you don't easily undo.
I have heard of people melting lead into the carriers for the same effect [ NZ Speedway in the 60's ] Whats wrong with welding the spiders [ the smart way is to remove the carrier bearings and Heat Treat the carrier afterwards ] I did this with a Lotus Cortina years ago [ the diff is still going strong after 10 years of racing ] I'm a big fan of locked rears in circuit racing
Nothing "wrong" with welding the gears, per se, especially in a racing setting where you're liable to break the carrier anyway. If you weld the spider gears in 9" Ford carriers and GM 10 & 12 bolt carriers, sometimes they will break in short order. Depends mostly on how they cool off after the weld (and how the weld was made, for that matter). For rear ends where they're available, a mini-spool is cheaper and easier (like $30 for one to fit a 9" Ford), and basically indestructible. However, Don here is hard core DIY (like he's some kind of DIY fundamentalist ), so I'm sure the thought of buying something never even entered into his head. I want to see pictures when it cools off.
Thanks Ryan. You have it. Your explanation was perfect. Buy is a dirty word here. If I cant make it I usually dont have it. I have a old diff in the housing I am shortening. Perhaps it will get new life next week. We shall see. Welding is not permitted in Drags. Mini spools often dont live. Spools work well but $$$$. Posis work for awhile this I think would have no chance of breaking . Nothing can turn and nothing can fall out. I will do my best to try it next week. I am thinking it is safe and inexpensive. To be honest I cant remember having such an interesting time as this foundry stuff. Sort of breathes new life into an old fart. Don
This is for a diff with slide-in axles - 8"/9" Ford, GM, Mopar, etc.? Sounds like it would work, other than possible shrinkage problems that CoolHand mentioned. A banjo rear wouldn't work as the (spider?) gears are integral with the axle shafts and are assembled from the inside out - this would make sense of Keerynzl's filling with lead, as that could be simply re-melted out of the diff if axle replacement was required.
Ich spreche nur mopar . (I only speak Mopar. ) Anyway warming or preheating the deal is a good idea and I will try that to as it will help for sure. Hadnt thought of the other style stuff. What brought me to this is a safe alternative to buying. Since all the dangerous stuff is safely encased forever I am thinking , hoping, this would work. In my minds eye anyway it is safer than a posi . Time will tell. Don
Take into consideration the excess stress of centrifugal force on axles and bearings due to the added weight of the carrier and any imbalance that it may put into your carrier...a few ounces may not seem like much, until you're at the other end of the track at speed...
Don I've never thought of filling the carrier but use to fill two cavities on each side of the spider gears with weld using 7018 rod then covering them and letting them cool and half way into the season we would have to build up were they were worn. On my banjo rear I had the carrier splined so it would accept 31 spline axles and act as a spool
exactly where are they illegal? is this a global policy? After he casts the aluminum, you are more than welcome to X-ray the carrier to determine if they are welded or not. rick
Don, if come you south for the winter, I think we can fix you up with a 10-12 pound ladle you could pour a few hundred pounds in a day.....I don't think you will break a sweat, now making all the molds and breaking them down well that is like real work. I'm still pondering the spool.......should work but why it hasn't been done before???? Thanks for posting your work it makes my day better! tt
Well they are not welded spiders and Vern knows that. I believe he is reffering to actual welded spiders which both NHRA and IHRA clearly forbid. This is a spool or will be. There will be no moving or breakable parts or welds involved. Vern and I used to inspect cars back in the day for NHRA. Vern still is active. He is often here for these adventures. I think I will be able to deal with the balance deal. Because it is so central it wont be huge anyway. Low centrifugal force. One must not forget that on many cars way down at the other end of each axle is a big huge chunk of cast aluminum which takes all of the loading. I believe it is called a wheel.
why it hasn't been done before???? NEVER and I do mean NEVER ask yourself or anyone else that question! Es ist verboten! I dont mind the work. I guess because I am always learning something the time and effort is a small price to pay. Don
A buddy of mine that used to run small time stock cars told me about how he got around a rule saying that spiders can't be welded. He bought square spider gears, no welding and it was locked solid. Good, bad, or indifferent... it worked.
since it has to be machined after the casting,why not start off with material thats going to hold up under extreme presure and have it heat treated ?like some 7071 aluminum, or some 4340 .i respect the idea of doing things yourself,but saftey has always been the rule of thumb.
I don't think you understand what he's got in mind. There won't be any machine work at all. He's just going to fill up an open diff carrier with molten aluminum and let it cool. That's it. No machine work, nothing, just a good cleaning before it goes back into the rear end. All the aluminum has to do is jam up the spider gears so they won't be able to turn anymore. He won't be depending on the aluminum to drive the car, so worst case, if it fails he'll have an open diff again. I'm not seeing the risk here. All the load bearing components are the same as they were before.
since it has to be machined after the casting,??????????????? no. $80 to $100? And this will cost me what? $0 except for a bit of propane. Aluminum is heat treated by quick cooling , water being the most common. Maybe I will throw a bucket of water on it but probably not. When you stop and think how little it takes to lock a rear end I think you have to come to the conclusion that it does not take much. When i was starting out in my trade one of the jobs I got a lot at the GM dealer was draining and refilling Posi diffs specifically in Oldsmobiles when someone had added normal hypoid instead of posi type. What would happen was when the car was warmed up like on a long drive at highway speed the clutches would get stuck and when turning of the highway they would hang on for awhile then release with a loud bang. I used to have to add an additive to combat this problem even after changing the oil. Later my own 8 3/4 cone types also have this problem from time to time. Otherwise what makes them both turn in unision is either some springs and clutches or cones or clutches and thrust from a sliding ramped spider shafts. I was often amazed at how little it takes to hold them. That being said I once tried pinning a set of cones but it only worked for a little while. Any slop and it can work lose. In a posi it just gives enough this is not a noticable problem. Mini spools do not work well in drag racing. i have seen several use them . One is a friend and I believe he used 3 or four before giving up.I investigated this unit with him and it was never broken persay just damaged because it isnt totally solid. A spool is. I reasoned that if I pour the open diff full of alumnum which for me is now easy to do the spider gears cannot turn. The axle gears cannot move. The spider gears and shaft are still all there and in contact. If I can get a solid fill there will be no slop. If I cant i fear it will succumb to the slop porblem. I can dream and talk and think till the cows come home or i can take 15 minutes, pull the diff out of the housing, Clean it out inside. Pack the important stuff like splines full of sand and pour it. Cost is for me zip. Then i will know. Aluminum is by weight stronger than steel. I believe it is around 27% stronger. So 2 pounds of aluminum a couple of inches thick reinforced with steel shafts and gears should be stronger than dirt. Also we talked about centrifugal force and balance. It will have to be decent but at 6050 RPM redline the carrier is turning only 1475 RPM with 4.10s. My furnace fan runs faster than that. I will know when I see it done if it is ok or not, if it is loose forget it but if it is tight and full and snug I think it will be super. I know only one way to find out. As for safety I do not take chances. I believe that if something can go wrong it will. When i work on something I dont do it to have a half-assed result. I firmly believe in a lot of cases that if someone else can make it why cant I? Like the pistons. If Egge can pour them why cant I? There is no reason. Just a learning curve which they had to make too by the way. I have tried a lot of things in my life. Other then jumping of the chicken barn with an umbrella (Yeah I did that) most have turned out good. My Dad is an engineer. He developed FM radio formobile use (GE) and synthisized front ends for aircraft radio. If you know about the Avro Arrow he designed the radios for it (Colllins Radio)and it was a milestone in Aircraft radio. (452 Channels instead of 9). Even though me and Paw have trouble being in the same room for long I did learn a lot from him and respect his knowledge and ability. One thing I remember clearly when i was trying something or thinking about it as a rambunctious kid and decided perhaps prematurely "aw it probably wont work" he would say to me this. "Well Don , one thing we can be sure of. If you dont try it , it wont work." I have learned to live by those words. (Dont tell him. He might get a swelled head) Now in retirement 13 years as of last month I have the time to try anything I want. Not everything works out but so much does it is frightening. Lately my old friend Vern who worked with me when I first came to Belleville 42 years ago has been here for many of the adventures. This recent idea just came to me friday when I was doing something else sort of related. I guess during a pour. I want to see what it turns out like. Good or bad I will post pics and my opinon for what it is worth. OK? Don
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