Disc swap using drum knuckles (1 Viewer)

[ijonesinsp]

Hello All,

I have recently acquired a set of front disc brake hubs and spindles from a ‘76 FJ40 for a disc swap on my ‘74 drum axle. My question is this:

Can I use my older drum knuckles with the newer spindles and hubs?

There are quite a few changes in these years and no real good answer that I have found. I would measure them and compare, but the older axle is still a roller for the time and I am trying to gather parts before I make the swap. Thanks in advance.

 

[pb4ugo]

I'm pretty sure the drum knuckles dont have provisions to mount the calipers.

 

[ijonesinsp]

I'm pretty sure the drum knuckles dont have provisions to mount the calipers.

You’re right. I didn’t even think about that.

 

[bikersmurf]

X2

That said, the ‘76 knuckles are a direct bolt on. You’ll need to swap to the fine spline ‘76 birfields as well.

Did that exact same swap back in about ‘94 when I converted the front to discs. Don’t forget a proportioning valve in the rear circuit and to remove the 10 lb residual valve from the front circuit.

 

[ijonesinsp]

X2

That said, the ‘76 knuckles are a direct bolt on. You’ll need to swap to the fine spline ‘76 birfields as well.

Did that exact same swap back in about ‘94 when I converted the front to discs. Don’t forget a proportioning valve in the rear circuit and to remove the 10 lb residual valve from the front circuit.

Thanks for the input! I have one the drivers side knuckle and birf. I’ll need to search for the other side before I do the swap.

 

[bikersmurf]

Thanks for the input! I have one the drivers side knuckle and birf. I’ll need to search for the other side before I do the swap.

You can reuse the inner axle. All you need is another Birfield to match your spindles and ‘76 freewheel hubs.

 

[ijonesinsp]

With leaving the rear axle drums, do I need a proportioning valve?

Also, where is this residual valve you speak of? On the master somewhere?

 

[peesalot]

The residual valvelives under the large fitting where the lines exit master cyl.
FWIW my 70 fj40 stock MC worked with front disc, rear drum, did not remove valves or use proportioning valve. It took 1 pump to get pedal with that set up. I putmetric GMcalipers and disc on the rear and it works really well now.