Axle assembly swap question

I'm currently facing a bit of a problem with an axle assembly swap. The 383 was too much for the old chunk. I broke the one-legger and am having a posi from an '87 police cruiser put in, but I had to go with a 5" bolt circle. My wheels (old Camaro rims which I like and have good rubber) are 4 3/4". My old axle splines are different, so that's out. I've heard of drilling the flanges for the other bolt circle, but no machine shop here seems to get it. I guess I'll have to do it myself (carefully!) Had to have the drive shaft cut too.

Any suggestions? I assume I should use the old drums and/or axles to make a template. I'd like to use my old drums and backing plates but don't know if the backing plates will work on that housing yet. I guess I can drill the drums on the "new" assembly if I have to, or just buy some. It's still in the shop now and I'm probably going to use old 5" BC steel wheels to get it home. Thanks!

You have 5 bolts in the new axle flanges. 360 degrees divided by 5 =72" between studs. You should be able to redrill the axle flanges in 5 places on a smaller bolt circle, offset 36 degrees from the existing studs, remove the current studs, and press in new ones on the correct bolt circle. This is not something that should be done "at home". In order to maintain the accuracy and concentricity that you require, and the bore specification for the newly drilled/reamed stud holes the axles must be removed from the rear-end housing and taken to a machine shop, where they can be set up properly in a Bridgeport mill and redrilled. This is not cheap, nor easy, but its the only way, unless you want to go to different wheels. At a minimum, allow 2 hours time per axle flange, counting set-up and machining time. That totals out at 4 hours shop time, generally costing minimum $72 per hour. You are looking at about $290 to get this done properly.

Thanks for the info, Brian. 300 clams - yikes! When I call the only machine shops here that would be capable of it, they sound rather unsure. It seems to me that IF the axle center hubs are the same size (I don't know if they are yet), I could just knock out the studs, turn the old drums around and mark the centers of the stud holes on the axle flange (making sure they are dead between the existing holes). Then I would drill small holes and measure to make sure before continuing. If the hubs are not the same size, it would be much more difficult, for sure. I know I would need some good bits and a lot of patience. So, you think it would be foolish?

It seems like aftermarket axles would be cheaper than the machine work, if Moser or somebody makes one like that. Especially since I can't seem to find a machine shop that wants to do it. They're in the 200 to 300 dollar range a pair, but after measuring the axles and counting the slines, etc., I'll probably find they don't make one.

Thanks, Denny! I'll check into those adapters - that might be the answer.

No, this is not something that I would try to do "at home". Being a cheap old dick at heart, I have tried just about everything that can be done to a car, by "doing it myself" to avoid costs. Because of that, I have learned about a thousand things that I can do, that make other people go "oohh,ahhhh, jeez are you ever a smart old bugger. On the other side of the coin, I have learned about 2000 things that ya just can't do without specialized equipment and have it work properly. Then you not only have to pay to have somebody else correct your mistakes, but you generally screw whatever it is you just tried to fix/do yourself so badly that the part is ruined beyond fixing, and so you have to first pay to replace the damn part, then pay again to have someone else with the proper equipment do it the right way. Any thing that involves a heavy weight (wheel and tire) rotating at a high speed, is something best done on a lathe or milling machine, or both.

Thanks, Denny! I'll check into those adapters - that might be the answer.

Well, if I've got enough wheel well clearance, the adapters sound like the way to go, if they have them. I have inquired about them. Otherwise, I'll need to make sure the right aftermarket axles are available before trying anything "adventurous." If not, I guess I'll have to ship the axles out, which I don't want to do, or just give up on my wheels. :CRY: First thing is I need the vehicle back along with some of the old parts. I'm not equipped for an axle assembly swap. Thanks again.

Go to www.moserengineering.com and check them out They do all the machining you need and very reasonable.
Charlie

If your 43/4 wheel fits snug on the axle flange center , you can redrill very accurately with just a drill press. drive out the old studs, measure center distance between holes,and mark a line. Lay on the rim,and using a large bit to fit in the lug hole,drill down just enough to establish a center on all 5 holes. measure your new studs,select proper bit, drill,drive. Hank

Well, that's sort of what I was thinking, Half, but Brian kinda got me scared off of the idea, at least until I was sure I could get aftermarket axles if I screwed it up. I respect where he's coming from, so I was going to be sure I had a line on the axles and I wouldn't be out anything but some sweat.

As it turns out, the guy who put in the assembly for me works fast - he's already sent out the axles to a machine shop to be drilled. I suggested that on Friday and he wasn't real confident about it, then I checked local machine shops myself and was even less so, but he's got a source I didn't have. It will be $130 for both axles, and it's a bonafide large machine, welding, and fabrication shop. cont'd

The adapters frome Goeske would have been a reasonable $130 for the pair, so that would have been doable.

Hopefully, all's well that ends well (until next time!) Thanks to all for all the good advice and info. I should be out of this sh**-eating Geo by Wednesday. It's OK for her, but you have to horse-whip that 5-speed through every gear just to get it down the road. Won't get out of its own way and gives manual transmissions a bad name!