3/4 Ton Brake Conversion

 

   
 
 

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 new brackets.

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.