RPO CODES

[dbrannon79]

That looks like a full floater. if the axle hubs were flush with the wheels then it would be the lighter duty rear end.

 

[MrMarty51]

That looks like a full floater. if the axle hubs were flush with the wheels then it would be the lighter duty rear end.

Yup, full floater all right.

 

[DieselAmateur]

From my research if you want to retain the 3.5" shoes you'd have to swap over the backing plates as they are recessed for the wider shoes. All else should be equal between the full floater rear ends.

And whatever you do don't scrap the 2.5" backing plates, they are discontinued for several years now and I have yet to see any new aftermarket support. Someone could definitely use them

 

[Will L.]

I know a lot of people prefer the full floaters-supposedly stronger iirc.
Personally, I hate em. Too much nonsense just to change brakes or anything. Easy mistakes for others before you to get preload on bearing wrong- the crazy heavy drum assembly in an awkward position means many people drag across the seal (me included). The ease at which the shoes cut into the drum and make a lip that you have to spend forever underneath backing off the self adjuster so the shoes clear the lip. The wheel bearings in my experience have more issues- probably because first mechanic sets pre load to a tight or too loose then the next guy does the opposite. A little chatter followed by to tight so more friction- or the other way around- it’s hard on bearings.

I wouldn’t avoid a truck because of full floaters- but I learned over the years that this rearend should fall under the “buy once cry once” theory of repair:

Leave the whole thing alone as long as possible. Then if the gears need reset up-start there and always new inner bearings regardless of condition - If not then just remove the diff cover.
Use a small pond worth of brake cleaner flush the entire axle assembly- then start putting it all back together. Nice new fluid in everywhere.

Rip down both sides of brakes- new shoes, dont turn those drums- replace them. All new shoes hardware kit. New bearings, races, seals. If the self adjuster clean up ABSOLUTELY PERFECT- fine, otherwise replace them too. Always replace the rubber seal that is access to the adjusters. One tiny road pebble has created more chaos in those than I wanna remember. Never a rebuilt slave cylinder unless you rebuilt it yourself. Factory new ones used to be available- idk anymore. Pull the new ones apart and clean them - then new fluid on the plunger seal and reassemble. If the cup seals on the end dont seal great- a fine wipe of permatex to ensure no brake dust ever worms its way into that slave cylinder. Remove the bleeder screw and antiseize the threads- being ultra careful to get none on the sealing angle. DON’T wipe off the bead of antiseize that rolls up outside the threads- Then a shot of enamel paint over the bleeder screw. The paint wont seal the two together where the antisieze squished out. It will be a tiny bead the size of one thread all the way around, encapsulated by the paint. The future you in a decade will thank you for this. Obviously you cant hit it with the paint until everything is done and bleed. Don’t forget the rubber cap. I have seen some guys never paint but instead do a fine coating of antiseize.

Oh yeah- those annoying brake cables- replacing them if in question. While the brakes are apart- a ton of brake fluid through them and spraycan graphite- absolutely soak them suckers in it. The graphite is a great lubrication and forms a small seal that makes the rust fight its way in. Some guys do the oil soak trick to the cables but I am always worried that oil will seep into the brake area and oil plus brake dust equals a nightmare.

Mind you- this is how I did it back when I thought nothing of 14-16 hour work days. Now that I can’t handle my regular job plus a couple hours at home-
That whole axle becomes a no go for me now. Now I would wanna run it to failure then do the gmt800 axle swap.

Someone mentioned rear brakes not as important as the fronts-
iirc rear should be above 40% of your braking capacity.
If using the skinny shoes as a grocery getter- ok. But if you ever squat that suspension- you better drive like a grandma. When we would tow heavy and they had the small brakes- it sucked. Brakes and like firepower- better to have it and not need it than need it and not have it. Never downgrade any brake system if you can help it. That 12” of sooner stopping might be the difference of stopping 1” away from that child in the street verses putting your front end 11” through them.

 

[DieselAmateur]

I mentioned the rears doing less work than the fronts more so in the context of the difference in braking power between the 3.5" rear shoes and 2.5" rear shoes. And my perspective is that if one is really wanting top of the line brake performance you'll see better results with the GMT800 front brake upgrade than swapping 2.5" for 3.5" shoes. Although swapping backing plates for the larger shoes is way less work and money than the 800 upgrade. Yes more is always better regardless, I just see levels to the upgrades, as the kids say

 

[ak diesel driver]

There's a bearing difference even on full floaters. I ran into this a year ago. I thought they were all the same. Nope

 

[jrsavoie]

Rip down both sides of brakes- new shoes, dont turn those drums- replace them.

I'm not sure I agree with that. I've heard enough problems with new drums to want them spun before installing.

If the old drums are in good condition, just have them turned.

Parts quality seems to be iffy.