Guess it wasnt the 3rd member.

[SteveL]

Thought I busted the 3rd member on the 66. Figured pinion or carrier. Just pulled it apart and it snapped an axle. Oh well should be easy fix. 351w pushing 35s with a small bearing rear. Mostly street driving.

 

[SteveL]

Just looked at the wh catalog. It's a small bearing out of my 72 bronco with disc so I dont know drum size. How do I know which axle to order? Any reason to do both sides?

 

[Apogee]

Sounds like you have reason to upgrade to 31-spline. Since you can't measure the drums, measure the axle offset dimension, outside of housing flange to rotor mounting surface on face of axle.

 

[DirtDonk]

A '72 small-bearing rear end would always have had the small brakes too from what I know.
So a 10" x 2.5" brake was what came on it originally.

Meaning that a pair of 31 spline axles is the #8600, or the single 28 spline axles are:
#8650 (right side) and #8652 (left side).

Paul

 

[Viperwolf1]

Use this chart to determine the axle(s) you need. Brake backspacing is same as brake offset Apogee mentioned.

 

[rjrobin2002]

What were you doing to break it? I had a hot 347 and 5 spd and was amazed at all the burnouts and drag racing I did with 35s and never broke one.

 

[SteveL]

What were you doing to break it? I had a hot 347 and 5 spd and was amazed at all the burnouts and drag racing I did with 35s and never broke one.

This bronco is more of a daily driver. Was just making a right turn going slow. There was a slight chirp and then no forward power. I've had a few stock carriers bust running 33s and 35s over the years. That's why I didnt pull it apart first to find the problem. After looking at the more recent wh catalog in pretty sure what to order. I'll be calling Monday morning for some parts.

 

[SteveL]

I plan on replacing the outer seals while its apart. Any need for rtv on the outside where the axle retainers bolt to the housing?

 

[DirtDonk]

Friend did that with two stock axles in a '70. But it had a Detroit Locker in it and somehow managed to break axles fairly regularly until he stopped putting stock used axle shafts back in!

Don't happen to have a locker in that '66 by any chance, do ya?

Paul

 

[Broncobowsher]

Reminds me of a friend who has a '71. Kept breaking stock axles with a Detroit. One day he decided to fix it with a set of high performance 28-spline axles. The better axle exploded instead of just twisting like the stockers did. Now it took out the Detroit as well. By the time he was into it for a couple of axles, a 31-spline Detroit, a housing that had a hard life, it was a complete new rear end.

 

[SteveL]

Open diff.

 

[blubuckaroo]

Did it actually twist off the axle, or just strip the splines?
I always heard that 33" tires was the most you should run on the factory axles.
Also, axles were designed to be the weak link in the drive train. By going bigger, you're just moving the weak link to the differential.

 

[SteveL]

Broke near the splines.

 

[blubuckaroo]

Broke near the splines.

Were you able to get the piece out?

 

[SteveL]

Were you able to get the piece out?

The axles are out. Didnt try to get the broken piece. I'm gonna pull the 3rd member out and make sure there's no chip or pieces in there.

 

[blubuckaroo]

Good call.
I've seen a broken spider gear cause an axle to break.

 

[SteveL]

Props to wh. I ordered the axle at 1pm Monday and it was on my porch the next morning when I got home from the beach.