brake drum to 9 inch mismatch?

[lilthom]

This project is on a 67 F100 but one of you will probably be able to answer my question since it is about a 9 inch. I swapped the 9 inch from a 1994 Bronco under this truck for better highway gearing. It needed all the brakes redone so I ordered parts based on the 1994 Bronco. The centering hole on the drums is just under 3 1/2 inches but the center of the axle end is only about 3. They work but have kind of bound up a few time when moving it around the shop/lot. They release on their own eventually. It's like there is room enough for them to shift. The parts store shows the same drum from around 79 to 96. What am I missing here? Brakes aren't my thing.
Thanks,

 

[bmc69]

The dif under a 94 Bronco would be an 8.8 and not a 9.

And no..you absolutely cannot run what you've got there..the drum is centered by that axle boss, not by anything else.

 

[McLeod]

Not sure where you are getting your parts, but the applicable range that encompasses the 94 Bronco brake drums is 1987-1996.

Like said, the 94 Bronco would have an 8.8" not a 9".

You either got the wrong brake drums or the 94 Bronco had a different than factory rear axle in it.

The picture does show a hole in the axle flange for access to the axle retaining bolts, so maybe the axle is a 9".

 

[Steve83]

Looks more like an '84 - those could have come with a 9", but even the 8.8s had an undersize hub stickout, like that.

 

[McLeod]

Is there a removable cover on the back of the axle housing or does the front of the axle have a removable center section?

 

[Rustytruck]

That drum is being located by the studs probably not good enough but I doubt that is the crux of your problem. Send some close ups of the brake shoes and springs. Check that the parking brake cables are properly routed and are actually releasing.

The shorter primary brake shoes go on the brake backing towards the front of the car and the longer brake shoes goes on the rear side of the brake backing plate and has the parking brake lever attached.

Check that the orientation is proper and you don't have all long ones on one side and short ones on the other side.

At one time I had brake shoes hanging up it was because there was grooves worn in the backing plate causing a ridge holding up the shoes on one side. I had to weld up the grooves and then smooth them back down and the other side I could just smooth them down without taking too much material off.

 

[lilthom]

I will have to check on all of these ideas this evening. I wondered about it being an 8.8. The new brakes and assembly were based on a 9 inch and fit in just fine. We will see tonight.
Thanks,

 

[lilthom]

Okay, this is definitely a 9 inch as I thought. My parts guy had to go back to 1984 to find a drum that had the smaller center hole. What I bought thinking this was a 94 has a 3.47 diameter vs 2.87 on my axle. I assume that the 86 drum will work just fine.

 

[lilthom]

That drum is being located by the studs probably not good enough but I doubt that is the crux of your problem. Send some close ups of the brake shoes and springs. Check that the parking brake cables are properly routed and are actually releasing.

The shorter primary brake shoes go on the brake backing towards the front of the car and the longer brake shoes goes on the rear side of the brake backing plate and has the parking brake lever attached.

Check that the orientation is proper and you don't have all long ones on one side and short ones on the other side.

At one time I had brake shoes hanging up it was because there was grooves worn in the backing plate causing a ridge holding up the shoes on one side. I had to weld up the grooves and then smooth them back down and the other side I could just smooth them down without taking too much material off.

Your picture is obviously looking at the passenger side. I have all of that on correctly.

 

[lilthom]

Looks more like an '84 - those could have come with a 9", but even the 8.8s had an undersize hub stickout, like that.

Looks like you win, this axle must have come from a 84, not a 94. The friend I got if from (for free) isn't much of a mechanic or car guy so he probably just wasn't paying attention.

 

[Steve83]

Looks like you win...

Ooh! What do I get?

 

[lilthom]

Ooh! What do I get?

Respect?

Thanks

 

[Apogee]

I assume that the 86 drum will work just fine.

You know what they say about assumptions...

That said, 1986 was the last year for production on the Ford 9" rear ends IIRC, and they were only used in limited applications. You should be fine so long as the drums are for a Ford 9" and not the ubiquitous 8.8.

 

[Steve83]

On FS trucks, the drums were the same for those axles. It's the ones for eBs that were smaller.


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