Rear disc vs drum

[TruckIt75]

Hey everyone I have a ‘75 Sierra Grande 3/4 ton with a 14 bolt rear, 8 lug and I’m looking into upgrading the brakes.
Recently put a 383 blue print motor, mild cam, headers and exhaust so the truck actually moves down the road a bit more now. I know I need to do pads and rotors up front but is the rear worth the hassle for converting?

 

[Ricko1966]

Hey everyone I have a ‘75 Sierra Grande 3/4 ton with a 14 bolt rear, 8 lug and I’m looking into upgrading the brakes.
Recently put a 383 blue print motor, mild cam, headers and exhaust so the truck actually moves down the road a bit more now. I know I need to do pads and rotors up front but is the rear worth the hassle for converting?

Rear disc is not worth the hassle. Fronts do the majority of the stopping and actually by inches in diameter drums have more braking force.

 

[Chevy 88]

It would be a nice upgraded, but probably not worth the trouble.

 

[ali_c20]

Hey everyone I have a ‘75 Sierra Grande 3/4 ton with a 14 bolt rear, 8 lug and I’m looking into upgrading the brakes.
Recently put a 383 blue print motor, mild cam, headers and exhaust so the truck actually moves down the road a bit more now. I know I need to do pads and rotors up front but is the rear worth the hassle for converting?

I switched to disks on my 74 C20 (14 bolt ff) because of the drums being behind the hub. The backing plates have no openings to reach the adjuster and I had a leaking seal which oiled my drums real good. I did it cause the disks are easier to check and service. I don't want to pull the axle if something is wrong or out of adjustment at the brakes.

 

[CalSgt]

Rear disc is not worth the hassle. Fronts do the majority of the stopping and actually by inches in diameter drums have more braking force.

I’m with Rick on this one, there’s nothing wrong with drum brakes especially on the rear of a 3/4 ton. Semi trucks loaded with 80K Lbs still use drums.

I have nothing against rear discs but feel they were a financial decision for new trucks as opposed to a performance decision.

I think discs were ultimately more cost effective for the amount of performance provided which led to 4 wheel disc brakes on the modern vehicles. If these trucks “needed” disc brakes on the rear GM would have switched long before they did.

 

[bucket]

Rear discs are nice for simplicity, ease of service, and good heat dissipation. But there's one thing that is often overlooked and is their biggest benefit- much better modulation for threshold braking. Drum brakes can act more like an on/off switch with not a lot in between. Locking up isn't stopping. Disc brakes inherently don't have that issue.

I'll also point out that there's an awful lot of big rigs out there now with disc brakes. It's an option that people pay for on purpose.

With all that said, the rear drums are already on the truck and if they are working fine, there's no real reason to do the swap, imho. If you spend much time in the mud though, disc's can be worth the trouble of the swap. But if the rear brakes are shot and need a good overhaul, I'd 100% go with a rear disc brake swap. It's a pretty simple swap on a 14 bolt full float axle. Cost is probably roughly the same.

 

[TruckIt75]

Thank you all so much for getting straight to the point. You all saved me quite a bit of time, money and headaches with this whole process.

 

[75gmck25]

I have a ‘75 GMC K25 with the FF rear axle and 13” drums and they work well. Only issue I have found is that if I leave the park brake on for an extended time (days) the linings stick a little to the drum. However, it would be a PIA to do any work on them because the axle has to come out before the drums come off, so I’m happy to just leave them alone.

I’ve also looked at rear disc brake conversions. Some folks make it work, but many seem to have issues. It’s not like it’s a turnkey solution, so results vary.

 

[GTX63]

Thank you all so much for getting straight to the point. You all saved me quite a bit of time, money and headaches with this whole process.

If you look back to when the trucks were new, they hauled quite of variety of heavy loads and equipment just fine. Unless you are looking to do a custom truck and have the money and time, drum brakes are fine.

 

[Beast496]

I did a rear disc conversion when I picked up this truck only because the rear drums were used up and in need of rebuilding. For me, at the time, it made since cost wise, I spent a couple hundred more for parts, but felt the ease of service makes up for it, not having to pull and reseal the axles each time.

 

[TruckIt75]

I have a ‘75 GMC K25 with the FF rear axle and 13” drums and they work well. Only issue I have found is that if I leave the park brake on for an extended time (days) the linings stick a little to the drum. However, it would be a PIA to do any work on them because the axle has to come out before the drums come off, so I’m happy to just leave them alone.

I’ve also looked at rear disc brake conversions. Some folks make it work, but many seem to have issues. It’s not like it’s a turnkey solution, so result

 

[TruckIt75]

Unfortunately it’s not as turnkey as I thought it was a week ago but I’d rather find this out now then when I’m elbow deep staring at a half apart truck

 

[Beast496]

Unfortunately it’s not as turnkey as I thought it was a week ago but I’d rather find this out now then when I’m elbow deep staring at a half apart truck

It's not as bad as some make it out to be. I had to make my own brake lines and weld some tabs onto the axle. Sourced a different proportioning valve and they work just like a newer truck. I used the Ruffstuff specialties kit.

 

[Bennyt]

I switched to disks on my 74 C20 (14 bolt ff) because of the drums being behind the hub. The backing plates have no openings to reach the adjuster and I had a leaking seal which oiled my drums real good. I did it cause the disks are easier to check and service. I don't want to pull the axle if something is wrong or out of adjustment at the brakes.

14BFF are notorious for leaks. My 14b leaked and there are repair sleeves available for them if you have a worn tube.

Additionally, there are 1-2 kits for 14BFF that use an entirely different type of seal.

 

[Bennyt]

In regards to the 14BFF, I don't think there is a disc kit on the market that can truly match the capabilities of the factory drums. That is a big drum that works very well.

I also haven't found a parking brake for a disc equipped 14BFF that works very well with the factory pedal. I've had to switch to ratcheting levers that have a substantial more travel and/or e-stopp system.