im swapping discs from a (i think) 80's cj onto a 73 cj. the bolts pressed into the knuckles are slightly longer from the disc setup (caliper bracket vs. backing plate). my question is, are the knuckles compatible or should i just swap the bolts? any info would be greatly appreciated.
I just did a similar swap on my resto '76 CJ5. The knuckles should be virtually identical from '76 through '78. The early '76 - 78' disk brake setups used the six bolt caliper support that attaches via the six spindle nuts. You should be able to just swap in longer studs and bolt everything right up. From '79 - '86 they changed to a two bolt caliper support that attaches to the knuckle.
When I started researching this swap I was going to use the 6 bolt style supports, which allow you to retain your hubs and outer stub axles. (You have to change the inner wheel bearing, the disk style spaces out the hub a bit more.) However, I was able to get a '79 housing / knuckle combination, plus axle shafts, hubs, rotors, calipers, backing plates, etc. from an '84 CJ7, all for free. By some miracle, all this stuff bolted right up, I was astonished! I swapped the 79 knuckles onto the 76 housing, then used all the '84 bits. I was able to keep the 6-bolt hubs off my '76 (rather than use the 5 bolt '84 hubs) by having the inside of the flange machined. I ended up using new the wheel bearings, calipers and front hoses. I found it a pleasant surprise that I didn't have to change out the master cylinder. '76 on CJ drum/drum masters did not use residual presure valves. Unfortunately, on a '73 I think you will have to change the master out, if you don't the master will hold a slight amount of pressure on the fronts and the calipers will eventually bind solid. Anyway, the swap worked out great, it now actually STOPS!
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