welding/redrilling rear axle flanges

I need to make a small bolt pattern A-body axle into big pattern, I bought a jig to drill the holes....The problem is my current axles have 3 holes in them all ready about where they need to be drilled. Has anyone ever welded up the existing holes? Do you think this could be done safely w/o changing the tempering/strength of the flanges?

Thanks for your thoughts
Rick

if it were me, i would purchase a set of axles from Dr. Diff.
by the time you get done welding the extra holes shut and drilling the new ones, it's hard to tell what will happen to the flanges.
just my opinion. your mileage will vary.

Dr. Diff does not sell replacement axles for the the 7 1/4 axle......

Just because it is small bolt pattern, does not mean it is a 7 1/4 rear end. 8 3/4's came with small bolt pattern too.

Keep in mind, IMO no reputable shop would do what you are asking, no matter what you are paying. The deal breaker for me is you are only welding three, and that means uneven heating/tempering on a stressed high rational catastrophic non redundant drivetrain part. Only thing that could be worse, is you want to drive it on the street.

Stock axles usually have the access hole for adjusting the axle endplay so that might make this a bad idea as far as not having enough material to work with.

If they are 8.75 axles then sell them and use the money to fund a large bolt pattern set.

This is a 7 1`/4 axle, yes the access hole to unbolt the bearing retainer will be welded up along w the other 2 holes and the flange redrilled. The axles will then be chucked in a lathe to make sure its still true and machine the welds flat. I will enlarge one of the old stud holes to make a new bearing retainer access bolt hole.

Not a smart move IMO.

Are the flanges and holes on a 7-1/4 any different than the ones on an 8-3/4?

I had a shop that builds custom rear ends redrilll my small bolt 8-3/4 axles to large bolt and thread them to install 1/2 inch thread in studs.
He installed new axle bearings at the same time.

They would install press in (knurled) 7/16th studs (GM I believe) but said the outside diameter of the Mopar 1/2 inch studs was to large but said thread in 1/2 inch studs would be fine.

If its a 7 1/4 just use 4" to 4 1/2" wheel adapters. The adapters are stronger than the gear itself.
Doug

This has been done on dirt track cars for years. I know they fall off in the corner and place tremendous loads on the right-side wheels.

I'm no metallurgist, so if it was me, I'd ask an axle shop, but I'd bet they'd decline doing it.
Other options:
Look for a pair of 5x4.5 axles, if there's a B-body or later A-body application.
Have axles made (Yukon, etc), though that's like throwing good money after bad.
Swap in an 8.75 and (1) be done with it and (2) upgrade.
Adapters, if available, though that probably creates a problem with wheelhouse space.
Get matching pattern wheels.

Adapters are an inch thick, then the wheels/tires wont fit inside the wheel wells.....no go

Wish you were closer, I have a 7 1/4 big bolt

40 some years ago a shop made a 1/4 inch thick ring that they press fitted over the 7 1/4 hub and then stitch welded it to the hub.
They then heated the hub up very warn but not hot and TIG welded the 5 ea 7/16 stud bolt holes up using a copper backer plate behind the weld.
Then they redrilled and tapped them for 1/2 inch screw in studs on the LBP.
That car had 4.10:1 Suregrip and we ran G60 15's for years.

I also have a set of 1974 Dart Swinger LBP 7 1/4 axles somewhere out in the garage. But not sure its a easy swap. Wheel bearings or splines may be different.

They did do a bearing change so you couldn't just swap over to the bb axles

Spacing for the brakes is different too.

Dutchman axle plugs and re-drills.

Dutchman

The 74 Dart Swinger \6 Auto had LBP and 2.94 SG. I kept the axle for my 65 B-cuda that was LBP (using 68 RR 4 piston front and Ford 9 inch rear). I ran that 7.25 for years but had an issue so I built a 8.25 using a truck's 8 3/8's SG and 3.55 gears. I put the 7.25's rear backing plates and 2.5x10 drums on that 8.25 housing. They fit OK.

The BBP backing plates and axles will swap around all 3 housings. They will not swap onto a SBP 7-1/4 housing. The tube ends and bearing sizes are different.

Welding on heat treated steel is NEVER a good idea. Ask a metallurgist, this has come up before. Even tack welding, which is probably worst than a complete weld.

And because this has come up before, there WILL be those that will tell their stories of how they did it and never had a failure. They just have not waited long enough. Sometimes its a lifetime, sometimes its minutes. Do what you will.

That's because the brake spacing issues is different with SBP axles. You didn't have one of those.

i didn't know that.
thank you for the correction.

The success of weld repairs on any metal is totally dependent on 1) material, 2) process, and 3) post weld treatment. If you know precisely what the original axle characteristics are, then go for it. Otherwise.... If it were me I'd call Dr. Diff and just chat for a while.

Much ado about nothing, people have been redrilling axle flanges forever. Filling holes doesn't require welding.

But I am assuming the OP's solution has little symmetry in the suggested process, and even with post weld HT, it is unlikely the he has built in for unaccounted potential stress risers, because of the location, different metals, grain structure, etc. The fact the wheel constantly, in use, loads and unloads the welded area unevenly, is a prime candidate for eventual fatigue induced failure.

The post weld HT is on a one off an educated guess if everyone knows what they are doing.

Regardless, no matter what the OP does, there is IMO, less then a 50% it will fail, but I would not do it.

I sent the axles off to Moser today, they say they can plug and redrill for $90 ea.

My buddy who was gonna weld em up did some research and found out that warping them was a real risk and his lathe is not set up at the moment, so he took a pass.

You should be good. About 35 years ago Strange drilled some holes in my stock A body 8 3/4 axles, did not weld any of the extra holes and both held up well on a mid eleven car, so...they put the 1/2-20 screw- in threads in there to save some "meat".