The Stovebolt Site Forums The Parking Lot Big Bolts Disc brakes for 1.5, and 2 ton trucks

Some questions you might have:
Q)Why not use a 1 or a 1.5 ton axle beam?
A)They are the same (as each other) and appear substantially lighter weight than the 2 ton. They use a 0.921" kingpin that is also much shorter and the thickness of the end of the axle beam is around an inch less, so not a good match for the newer spindles.
Q)What are these axles rated for?
A)A P-30 axle is rated about 5,000 lb, and the 2 ton is rated 4,500-5,000 lb, nice that they are so similar!
Q)What's the difference between a P-30 5/10 lug axle and a 3500HD axle?
A)The main one we'd be concerned with is the steering linkage. The P-30 is setup like our old trucks are with tie rod behind axle under springs, the 3500HD has tie rod on front and above springs, and drag link is there too.
Q)Did they ever make a single wheel P-30 disc brake axle?
A)No, if it has disc brakes it will be a dual wheel type axle


If these disc brake swaps revolve around swapping newer P-30 spindles onto old AD axles there needs to be some similarities, here they are:
The thickness of the I-beam axle end where it fits into the spindle is the same for both P-30 and 2 ton AD axles, About 3.050".
The angle that the kingpin leans in, known as kingpin inclination angle, best I can measure is the same for both axles.
Kingpin length is essentially the same, and the lock pin groove is in the same place.

Now it would be to easy if everything was the same... here is the major difference:
The kingpin diameter on the 2 ton axles is 1.109", and on the P-30 it is 1.179".

Two methods of adapting the P-30 spindles to the old axle:
Use thicker walled bushings, but I've been unable to find any ready made ones. You can order oversize bronze ones and turn and bore them to suit, probably have to mill the grease groves too.
Or you can make thin sleeves to press in the kingpin bores in the spindles to adapt them to the original size smaller OD bushings. So far I like this idea best. I'd use green loctite sleeve retaining compound so they stay put, and in the future new kingpins and bushings are an off the shelf item.

The 1.109" kingpin kit you would use is NAPA # 262-1016. There are other similar kits but this is the best choice from what I can see because it comes with gaskets for the caps on the P-30 spindles, not steel plugs like the old 2 ton had, it has bronze bushings not plastic, and has a ball thrust bearing not a thrust washer. It's also cheaper and easier to get than the other possibly suitable kits.

Grigg