I'm sorry I didn't see this sooner.
You have made some mistakes.
You should not purchase a rear disc kit, to upgrade the 10-bolt axle. Perhaps you can send it back.
You do not "have" to re-gear. You can if you want. Re-gearing has it's own little problems, like getting the speedometer to read correctly afterwards. Solve-able, but with additional labor and frustration.
As said...stay away from disc brake conversions, especially on a 10-bolt axle. The 10-bolt axle is fragile, it's not worth spending a lot of money on. Get a better axle, which may come with better drum brakes--solves both problems, likely for less money than the disc conversion alone.
Be VERY careful.
You almost certainly have "JB5" brakes now. That means you have the "good" front caliper and rotors, plus the "good" master cylinder and booster. IF (big IF) the front brakes and master/booster are in good condition, there is NO REASON TO MESS WITH THEM except to assure that they've got fresh, clean, dry brake fluid instead of dark, icky, wet brake fluid + sludge. Granted, there's a pretty good chance that the front calipers have sticky pistons, or the calipers are sticky on the mounting pins. This is easily resolved by rebuilding or replacing the front calipers. Same goes for a master cylinder or booster that's seen better days--there's NOTHING WRONG with the OEM parts if they are in good condition.
JB5 Caliper before clean-up. Nobody flushes the brake fluid often enough. These calipers "worked" but the pistons were sticky. Not seized, but not as free-moving as they should have been. COMMON AS DIRT. I cleaned 'em up, they're on my truck now and working great.
You must be registered for see images attach
The complication is that the front calipers are GM low-drag units, for better fuel economy. The low-drag calipers need a specialized master cylinder with THREE chambers--the usual two high-pressure chambers, plus a third low-pressure, high-volume chamber that pushes a big gush of fluid to the front brakes. These are called "Quick Take-Up" master cylinders. The high-pressure chambers are modestly sized (1 1/8 inch diameter) so that pedal effort is reasonable under heavy braking; or if the booster fails for some reason.
Quick Take-Up master cylinder--step-bore, casting has a step at the rear for the high-volume, low pressure section. Note the large diameter of the rearmost seal compared to the ones in front.
You must be registered for see images attach
You install some aftermarket master cylinder that doesn't have the third high-volume, low-pressure chamber, the diameter of the two high-pressure chambers has to be much larger. This destroys the hydraulic advantage of the smaller master cylinder diameter versus the caliper piston size. Much higher pedal effort if the booster fails, and it's a needless risk caused by MIS-MATCHED PARTS sold by UNETHICAL VENDORS who don't seem to care that they're SCREWING UP the front brakes. (I've heard that there's a tiny warning about using the master cylinder you bought only with "their" "front caliper upgrade"; but I've never researched that for myself.)
IF (big IF) your booster and master cylinder are in good condition, DON'T DICK WITH THEM. If they've got excess wear, or are somehow giving you trouble, replace them with the parts that are supposed to be on your vehicle. Do not downgrade to a two-chamber master when the front calipers need a three-chamber "Quick Take-up" master.
As for the rear discs, you don't need 'em. Disc brakes at the rear are not magic, and sometimes you give up the park brake which is another bad choice. Yes, you probably have the really-crappy 254mm (10-inch) leading/trailing shoe rear drums. They're horrible. They should never have used that design on a full-size truck. GOOD drums are all you need, and will likely cost MUCH less than a disc conversion, while keeping the park brake with no fabrication or special park-brake cables or hardware.
But the 8.5" 10-bolt rear axle itself is another bad choice; it's just plain not strong enough. It's the minimum they could get by with. I've seen them where the differential case is completely exploded, leading to big chunks missing from the iron housing.
Solve your rear brake problems by upgrading to the 11.x, Duo-Servo rear drums from a...Tahoe or Suburban, I think. Maybe vans. The SUVs and maybe the vans got the "good" drums even though the pickups got junk rear brakes. You should be able to find the "hard parts" at a Treasure Yard for cents on the dollar. Buy new shoes, new hardware kits, maybe cut the drums. "JB5" front brakes and master cylinder/booster, plus the 11.x rear drums = JB6 brakes.
When it was me, I bought the bigger, stronger 9.5" axle from a 6-lug K2500, that already had the better rear brakes. About $500 in parts. Then I sold my worn-out 6-lug 10-bolt to my buddy with an exploded 6-lug 10-bolt. But that swap is harder with a C1500 than with a K1500 due to the 6 lug studs on the bigger axle vs. 5 on yours.
Last edited:
