Hydroboost and right rear dragging

[Blue Ox]

I dont have hydro boost and i still have drum brakes in the back of my 78 but i have issues pretty much the same as yours. Randomly if i touch the brakes, even a gentle press the right rear locks completely and squeals the tire. It seems to be completely random too.

We were having a discussion around the shop and my tech suggested a wheel seal leaking gear lube onto the shoes can cause this too. Another thing to look at.

 

[78C10BigTen]

We were having a discussion around the shop and my tech suggested a wheel seal leaking gear lube onto the shoes can cause this too. Another thing to look at.

Mmmm... well thats a safe bet knowing my rear isnt healthy, i bet it is the seal. Thanks for the input.

 

[LGDH]

A couple of things to add, I had 13” drums on one of my trucks and had rear lock up problems, bought new drums and problem went away....for a while, turns out they had gone out of round as had the ones I’d replaced. So I converted to discs using a kit I bought from the states, a great move. As far as the rear right locking up, despite having new flexible hoses I’d check that fluid isn’t getting between the hose layers. I’ve had that happen before, the pressure goes to the caliper and also closes the hose off stopping the fluid from returning back to the master cylinder, this may be even more of an issue with the higher pressures of the hydro boost system. I hope it helps

 

[Warkmeister]

I just wanted to give an update to this situation. I flushed the system and replaced the old proportioning valve. Not sure if this made a huge difference, but I had a disc/drum valve in before, then switched to a disc/disc by removing the rubber plunger from the rear line output as shown here...(http://www.classicperform.com/Instructions/PDF/Prop_Valve_Mod_Instructions.pdf)
I’ve heard that the disc/drum setups hold or provide 10lbs pressure in the rear while discs only need 2lbs. I tested it out and found I still had some drag. I pulled the wheel while it was all tight, and found out it was actually the caliper bracket itself that was causing the problems. It was maybe 1/16” out of parallel to the axle surface (imagine a shallow bent “Z” with one arm slightly off) I beat it straight with the BFH and tested again. Problem seems fixed! The outside caliper pad on that wheel was wearing unevenly along its top edge from being pinched ever so slightly crooked while braking. Hope this helps anyone else having rear disc conversions on a 14 bolt.