3/4 Ton Brake Conversion
I recently swapped some Dana 60's under my rig.
The rear axle had 3/4 ton brake hardware (disc conversion) but the front axle
still had the stock 1 ton brake hardware. All the 1 ton brake components are
physically massive and the calipers use a single large piston which requires a
lot of fluid to actuate. On the truck these axles originally came on I am
sure the master cylinder was boosted enough to allow the driver to have good
braking performance. On my buggy with a 1" Firebird master cylinder
and small Samurai booster I have to really press down on the pedal to get the
brakes to grab, they feel like manual brakes with no assist. To get better
braking performance I decided to convert my 1 ton brakes on the front axle to
3/4 ton brakes. This swap allows me to use 3/4 ton calipers which have a smaller
piston and will also drop some weight since all of the 3/4 ton components are
smaller than their 1 ton counterparts.
The heart of this swap is the caliper brackets,
I purchased a pair of 3/4 ton conversion brackets from Sam's
Offroad. There are many places that sell these, be aware that the
brackets need to be offset on the top, flat brackets will not work properly and
will need spacers for proper caliper/rotor alignment or require you to attach
the spindle to the knuckle in a way that affects the strength of the two parts.
The new 3/4 ton bracket is shown above on the left (5.5lbs), the stock 1 ton
bracket is shown on the right (11.5lbs), approx 6lbs per side is saved with the
Next up were the rotors, 3/4 ton shown on the
left and 1 ton shown on the right. From here on out all the parts I
purchased can be had from pretty much any auto part store and come from a 77
Chevy 3/4 ton 4wd (K20). After 1978 the brake fitting on the caliper went
to a metric thread but other than that the parts are pretty much the same. These
particular rotors were from Autozone, P/N 5523 and ran approx $25 each. They are
slightly thinner than the 1 ton rotors and have more material removed from the
hat area netting a 6lb weight savings per rotor.
The final parts used in this
swap are the calipers, Autozone P/N C502 and C503 approx $11.99ea with a
$10 core charge. As you can see the calipers are physically smaller than
the 1 ton originals and the piston on the 3/4 ton calipers is also smaller,
2.75" dia vs 3.25" in dia. The brake pads used are P/N
MKD52SV (Semi-metallic) and ran $9.99. These are also much smaller than
their 1 ton counterparts.
The total net weight savings between the two
different loaded caliper sets is 8.5 lbs per side (1 Ton was 19.5lbs, 3/4 ton
was 11lbs). To attach the calipers to the new brackets I used a pair of hardware
kits P/N H5004 (2 pins per kit) which ran $3.99 each. The last thing I
needed was a pair brake lines. The existing lines I had use a smaller
banjo bolt. The brake lines for the 77 Chevy calipers are part #77028 and
use a 7/16-20 banjo bolt.
After some usage I can definitely say the braking
performance is improved. Before the swap I found the pedal would be hard
after the first 1/4" of throw and I would have to stand on the brake pedal
to get the rig to stop quickly. Now the pedal feels much more linear, and
it only takes a moderate effort for panic stops or holding the brakes on a steep
incline. The total weight savings came in at a whopping 41lbs! Very
impressive for a relatively cheap and easy modification.