Originally Posted by Fix Until Broke
Commercial Chassis front spindles
- Use a "Set 5" inner front wheel bearing which has a 1.375" spindle diameter whereas the wagon/sedan spindles use a "Set 6" which is 1.250"
- The outer wheel bearing is common between the two - "Set 3" with a 0.8437" spindle diameter (for the later cars)
- Need to verify if the commercial chassis hub bearing spacing is different than the wagon/sedan - is it just a larger inner bearing or are there other dimensional/positional differences as well
- Tie rods (both inner and outer) have different part numbers vs the wagon, but share the same 11/16-18 thread at the adjuster
- Need to verify if rear dust shields are same between wagon/sedan and commercial chassis. If so, there's a chance at one of the big brake kits being able to be used
- Need to verify if the Commercial Chassis spindle has provisions for ABS sensors - is a must have for my application.
At this point I'm considering the Commercial Chassis front brakes a "nice to have" - I'd like to have the larger wheel bearing size, but in reality, it's only 300lb heavier than stock (on the front end) which doesn't feel like a lot. So if I can make one of the big brake kits work with the larger spindle bearings without reinventing the wheel, then I'll probably do that, but otherwise guessing it will be fine as is.
I'm more nervous about the 8.5" 10 bolt and surviving long term sustained loads - we'll have to see how/where it measures up unless someone has measurements of one of these rear ends (9.5" 12/14 bolt from a commercial chassis).
If the chassis you're getting does not have ABS, (assuming model year is 91 or newer), the front end is going to be J55. If it has ABS, it's the same as all other "B" applications, right down to 9/16" lower BJ. 1/2" wheel studs is the other giveaway for J55.
See photos below--I do have a pair of new-in-box J55 knuckles - 18021054 & 18021055. Lower ball joint is 5/8", and the casting is otherwise identical to JA9 for 95-96 9C1. Only differences are the larger spindle pin for Set 5 inner bearing, the tie rod taper, and the ABS sensor bosses are there, but blanked--it would require a machinist to bore the hole in the casting and thread the hole for the sensor retaining screw.
I'm confident there's sufficient material on the J55 rotor to cut the step on the back to add the 34T ABS tone ring from a standard 91-96 B-body rotor.
I haven't read the entire thread to grasp what your objectives are, so it's not clear what would be of the most benefit/bang for the buck to get you there. I do also have some modified original 9/16" ABS knuckles (18021052 & 18021053), ready for 5/8" lower ball joints, if that helps.
I see that HD12 and Astro mod have both been mentioned. HD12 uses the KORE3 billet HD hub that also is part of their big-brake kits. Astro uses a cut-down stock rotor, turned into a hub. Both are standard Set 6 inner, Set 3 outer.
The dust shield holes on the J55 knuckle are the same, so everything is there to do something "big brake", but it would take a cut-down J55 rotor, or a custom KORE3 hub for the larger inner bearing--and I still don't know the answer as far as inner/outer bearing seat distance being the same or different.
One last thing--if you stay with the B-body knuckles, for improved strength, probably equal to J55, get the bearing pre-load spacer kit
I can't help with the rear axle--the wagon 8.5" is pretty beefy, with 1.6" diameter axle shafts at the bearing journal, compared to 1.4" for sedans. Swapping in a Limo 9.5"--no idea where that takes you. WRDC takes care of the park brake function, if it was not clear.
Photos 1-3 are of the FW non-ABS knuckle for J55 brakes. The area for mounting an ABS sensor is blank.
Photos 4-6 are of the standard B-body knuckle with the provision for ABS, and JA9/JB9 or JM4 spec brakes. The area for mounting the ABS sensor is clearly different, as it has been machined to accept the sensor and bolt.
Same casting, minor machining differences for tapers & ABS sensor, and the spindle pin is larger at the inner bearing on the J55 version.