521 axle swap questions

[Dalesun]

So I've been searching around and haven't found anything about swaping rear axels other than a bunch of stuff about gear ratios. My rear bearngs make this grinding rubbing noise when I drive or lift the rear end up and spin it by hand. My friend has an axle from a 1978 620 and I was wondering how to hook up the e brake cable from my 521. Also the brake line comes down to the axle on the right for the 620 one and my 521 has it coming down on the left side. Can I take my brake lines of my axle and put them on the 620 on so they match up or is there a different way to do this?

[wayno]

The 620 axle might be a little wider, maybe an inch or two, but I suspect it will fit your 521 fine, as I have 720 axles under mine.

You need to transfer all your 521 e-brake hardware(cables) onto the 620 rearend, then it work like it's supposed to.

The brake lines are a different story, the 620 lines are metric, while the 521 lines are SAE, so this means you will need to figure something out, I would generally reverse the 620 brake lines on the rearend, left on the right, right on the left and make that part work by re-bending where needed, then I would cut the upper connection  and put a metric fitting on the SAE line so it will connect to the hose, but that requires you to double flair the line when you cut the old fitting off and replace it with the new fitting.

 

I am used to making my own brake lines, so this aspect of it doesn't even slow me down.

I actually have a couple 520/521 rearends in the back yard, I am not sure of there condition, but I will sell one them to you.

 

You might have to PM me if you want to talk, I don't get to/check this section a lot.

[spottedog]

I had that kind of sound on my 74 B210, it turned out to be a really wasted rear wheel bearing. (Much easier fix than replacing the rear axle)

 

But the rear of the car on GOOD jack stands, Block the front wheels, leave the rear  wheels on (so you have some weight partially loading the bearings)

Start the engine and put it in 2nd gear, let it idle.

 

Take a broom handle (or long stick) put one end of the stick on the brake backing plate close to the end of the axle tube, hold the other end of the broom handle to to

your ear. If the wheel bearing is shot, you will hear it easily.

 

Note: Generally due to the action of the differential, only one wheel will will be turning, to check the side that is not turning, wedge a rock under the tire that did turn

and the other side will turn now. SHUT OFF the engine put the rock in position, then start it back up.

 

While the car is on the stands, put your broom handle on the differential housing to check for ugly noises there.

 

Good to have a helper for safety.

[Dalesun]

thanks for the input guys. I have never worked withh brake lines before so idk about doing that right now. As for the bearings I can spin them while the rear end is jacked up and can hear it pretty good. Can hear it too while driving and I get a wobble at 40mph and after 45 ish it goes away. Will look into replacing the bearings for now or get a 521 rear end from wayno cause I also drilled out my hubs to fit in new lug studs that didn't quite fit in all the way so I had to go up a size and idk if that is giving me problems now

[wayno]

thanks for the input guys. I have never worked withh brake lines before so idk about doing that right now. As for the bearings I can spin them while the rear end is jacked up and can hear it pretty good. Can hear it too while driving and I get a wobble at 40mph and after 45 ish it goes away. Will look into replacing the bearings for now or get a 521 rear end from wayno cause I also drilled out my hubs to fit in new lug studs that didn't quite fit in all the way so I had to go up a size and idk if that is giving me problems now

 

This sounds like you could have other issues, what do you mean you drilled out your hubs, did you drill them with a drill press, or you just stick the drill bit in the hole and eye it?

I had a vibration that I could feel/hear for 1mph till about 40mph, then it would smooth out, it turned out to be a lose wheel, so if you changed your studs out, and the lugnuts do not fit properly in the wheels, you could have loose wheels.

[mklotz70]

If you do swap to another diff with metric brake lines, I would just get a generic SS braided line to connect the hardline on the frame to the union on the diff.  You could get SAE on one end and metric on the other, then you don't have to mess with the hardlines at all.  You may be able to get away with just a brass adapter like I use with my brake kits.

[Dalesun]

If you do swap to another diff with metric brake lines, I would just get a generic SS braided line to connect the hardline on the frame to the union on the diff.

You could get SAE on one end and metric on the

other, then you don't have to mess with the hardlines

at all. You may be able to get away with just a brass

adapter like I use with my brake kits.

That is a good idea. Will see about geting that.

 

 

And does anyone know what all has to be done for the ebrake to still work?

[wayno]

That is a good idea. Will see about geting that.

 

 

And does anyone know what all has to be done for the ebrake to still work?

 

As I said, you need to transfer your 521 e-brake cables to the new rearend, it will work the same on a 620 or 720 rearend.