[dwcsr]

The output pushrod, retainer and spring is for some reason not available thru GM, in fact if you go looking for it they will undoubtedly tell you that either Gm has not used Hydroboost since the early nineties or that they never put it in a 1500 pickup. They may even ask for a vin # because they can’t do anything without a vin #. Call the junk yards and say “you gata hydraboost for a 2000 silveraada” they say “yup” you say “ow much” they say “75” you say “yank it I’ll be over”. Now that’s a transaction, nobody wasted time and we both got what we wanted. I got the spring retainer, spring and rod out of the junk booster. I’m sending the old booster back for a $50 core charge so I really paid $25 for a used master and the rod and spring.

The spring and rod are an important part in the system; the spring puts tension on the booster piston so it releases the pressure on the rod and doesn’t stay engaged to the master and drag the brakes when you let off the brakes. The disc on the inner end keeps the rod centered in the booster rear cup and the retainer of course keeps the spring in but also centers the rod to line up with the master cylinder indent. If the rod were to drop out on either end it could cause your brakes to apply and not release in a panic stop of just plain fail. So if your fabing these pieces remember these dimensions are for a 2001 Silverado 1500 with 4 wheel disc brakes, the Hydroboost and master cylinder are for the same truck.
I have no idea if the rod and spring is the same for any other year or model truck.

Rod diameter 0.34” with a length of 3.16” it appears to be as hard as a grade 8 bolt.
The rear spring disc is .970” diameter with a thickness of .040” and placed .25” from the inner end and it is made of plastic.
The spring is 4” long and .945 diameter. The wire thickness is .073. It feels like a 20 – 25
Lbs. spring tension.