i am trying to find a rear axle. my passenger side keeps locking up. I have done everything but change the axle...

 

Have you checked out your complete brake system?

Could be your brakes sticking on that side.

 

Check your parking brake cables. Could be one of them is not releasing all of the way. Look underneath on the driver side. Manually pull the parking brake cable where the two meet at a bracket, they should spring back when you let go. If they don't replace the cable or cables.

Also could be a bad rubber brake hose.

 

Is it mechanical or is it hydraulic? What I mean is, when the wheel locks up, can you back off the adjuster to free it, or do you have to unscrew the bleed valve to relieve the pressure?

I have had the same problem with my truck and had to unscrew the bleed valve to relieve the pressure . I recently replaced the rubber brake hose (http://broncograveyard.com/products/cat/20/163/32550A). After bleeding the system, it seemed to fix my problem. Your mileage may vary. I have also heard that this problem is caused by a faulty RABS valve. I bought one, but have yet to install it.

Hope this helps.

-Richie
1989 F-150 XLT Lariat 4x4