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Nuts & Bolts: Disc Brake Conversion for 1985 Chevy K10

Posted in How To: Suspension Brakes on October 9, 2015
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Photographers: Trenton McGee

10-Bolt Dilemma
I have a 1985 Chevy K10 and I recently blew up the original 10-bolt differential. I'm in the process of installing a 9 1/2-inch 14-bolt six-lug. Does someone make a disc brake conversion for this axle? I can only find the kit for a 10 1/2-inch eight-lug. Or do you think I would be better of installing a full-floater 14-bolt 10 1/2 with a six-lug conversion?

The 9 1/2-inch semifloating 14-bolt is a significant upgrade over the stock 10-bolt, and if you got the axle for free or nearly free, then it's a good swap candidate. However, like your 10-bolt, the semifloating 14-bolt uses C-clips to retain the rear axle, so if you break a shaft, you had better have a spare with you. For this reason and a few others, the 9 1/2-inch 14-bolt axle isn't a very popular swap candidate. Still, it's a six-lug axle and nearly a bolt-in replacement for the 10-bolt, so it's a better option than repairing your truck's broken 10-bolt. There's a possibility that GM offered the 9 1/2-inch axle with disc brakes from the factory during the axle's 16-year production run (1997-2013), but there's no telling what the application might be. It sounds like you already have the axle, and if so, it's going to be easiest to stick with the drum brakes that are already present. You might be able to mix and match or adapt disc brakes to the axle, but it's probably going to be more trouble than it's worth.

Depending on how hard you use your truck, I would opt for building a full-floating 14-bolt if you are going to go through all the trouble of swapping an axle. It doesn't get much stronger than a 14-bolt, and both hub conversions (to get six lugs) and disc brake kits are readily available. Plus, they command about the same prices in junkyards as the lighter duty axle. If you plan on keeping your truck for a while and using it hard, the full-floating 14-bolt is by far the best option.

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