rear disc break conversion - what is needed to work with factory rear end?

[paradigm]

I have an '86 Monte Carlo SS, and ever since I pressed the brake pedal with the left rear drum off, I have never been able to get the rear brakes to function correctly. They were either too loose, or now they are too tight and dragging. I cannot get the adjuster teethed mechanism setup right, it keeps falling off.

I am thinking about swapping to rear disc brakes. Is there a cheap and easy way to get this done to retain the factory rear end and axles, or must all of that come out?

I am seeing kits on Amazon, Jegs and Summit for around $350-$450 but I am not sure if those have everything I need to do the swap:

https://www.jegs.com/i/JEGS/555/631476/10002/-1?gad_source=1&gclid=Cj0KCQjwytS-BhCKARIsAMGJyzqnVYQDek3wk3Ycr7qPIe80r_6kDWwxjF-ox6wPCMEeuIJr1LNPVP0aAgcJEALw_wcB

https://www.amazon.com/Inline-Tube-Replacement-Compatible-Conversion/dp/B01CD58S8U?tag=gbody-20

Inline tube has a nice video here, looks like the only welding is the brake line tabs to the axle tube. Do you guys re-use the factory brake lines for this swap?

I have also read of people using Fbody rear brakes, and other GM OEM rear brakes to do the swap? What is needed for this swap and how much should I expect to pay?

 

[Ribbedroof]

Concerns I see with those kits....going to need a different master cylinder to support the fluid volume, possibly proportioning valve, and the calipers are an OLD design that had a limited number of OE applications which might be an issue down the line for obtaining replacements if needed. Or maybe not.depends on how popular service parts for those remain . Pretty sure no parts store is still stocking 79 Eldorado calipers so there would likely be some down time if replacements are needed.

More concerning to me is that you can't make the drums work properly. Sounds like the lower spring is missing/improperly installed if the adjuster keeps falling out.

 

[86LK]

a cheaper conversion to disc is the old 98-05 Blazer which had rear discs. you can also use the front disc from that same vehicle for a better front braking experience. plenty of videos online showing how to do that.

an alternate drum braking solution is to replac the cylinder with one from an S10. you get a bigger bore with increased pressure.

 

[Bonnewagon]

Those calipers say Eldorado, but I believe they are also the 1979-81 Trans Am rear calipers. VERY hard to find. I know the only way to get rebuilts is to send in your units for servicing. Stainless Steel Brakes used to offer stainless sleeved rebuilts. I'm not sure if they do anymore.

 

[Clone TIE Pilot]

With a rear disk brake conversion you need a new proportioning valve that is setup for 4 disk brakes. Converting from drums to disks requires a complete system replacement as all the parts must match.

You probably will need a new rear brake hose unless it's been recently replaced. Old hoses can internally swell but look OK from the exterior.

 

[paradigm]

Concerns I see with those kits....going to need a different master cylinder to support the fluid volume, possibly proportioning valve, and the calipers are an OLD design that had a limited number of OE applications which might be an issue down the line for obtaining replacements if needed. Or maybe not.depends on how popular service parts for those remain . Pretty sure no parts store is still stocking 79 Eldorado calipers so there would likely be some down time if replacements are needed.

More concerning to me is that you can't make the drums work properly. Sounds like the lower spring is missing/improperly installed if the adjuster keeps falling out.

I just removed the drum and this is what it looks like underneath, does it look like there may be a missing lower spring here? The area circled in yellow isn't latching in properly, and I am smelling my rear brakes overheating.

 

[Ribbedroof]

There should be a spring above the adjuster

That spring preloads the adjuster

This is not a G body axle but is typical of a GM rear drum brake

 

[Bonnewagon]

I once installed the adjuster screws backwards. When I hit the brakes they self-tightened up. They should only self-adjust in reverse. Swapping them from side to side cured it.

 

[565bbchevy]

does it look like there may be a missing lower spring here?

It may be rusty but it looks like there is a lower spring in there going across above the adjuster, maybe check the condition of that spring. It should have come new in the hardware kit.