Description
The Dana 70 brakes on the rear of your truck are drum brakes, and when you push on the brake pedal, fluid pushes your brake shoes against your brake drums, and your truck stops. The part that makes all this work, are your wheel cylinders. However after 30 years, these cylinders are prone to leaking, or plain giving up the game.
There were three different wheel cylinders used on the 1st Gen Cummins trucks:
7/8″ – For 250 trucks with 2.5″ shoes
1″- For 350 single rear wheel trucks with 3″ shoes
1-1/8″ – For 350 dually trucks with 3″ shoes
Do note the left and right side wheel cylinders are different and are side specific. Also note that the wheel cylinders are the same for 2wd and 4wd trucks.
A common upgrade when wanting more braking power and rebuilding your brakes, is to use a 1-1/8″ cylinders on your lower tonnage trucks. Do be aware to do this, you will need the 3″ shoes, and also new drums unless they were already using 3″ shoes. Also be aware that if you have bypassed your rear ABS valve, this upgrade will make your rear tires skid and lock up.
