DULLY BRAKES

1998 V-10 dully, changed front pads 2-3 times 160,000 miles normal with 10,000lbs towing, had to do rear axle seal this weekend. rear drums 13" shoes look fairly new have never changed since new, , are they not working?? what do I check?? I know fronts wear faster then rears

When you do an oil change, adjust the back brakes. Yes they have self adjusters but that only helps when you back up. How much time is spent going forward using the brakes compared to reversing and using them? Doesn't take long before the adjusters have no effect. Simplest way I found around that was to manual adjust them at every oil change.

Dually. Use the the parking brake? That should help keep the shoes adjusted as well.

The trick back in the day was to substitute a dually Chevy wheel cylinder. 15/16" diameter if my memory isn't completely corrupted. After I bought my 01.5 with rear discs I forgot all about the older trucks brakes. Head and shoulders better than my '96 dually, that alone made the trade worthwhile.

yep, someone on classracer swapped gmc .125 bigger bore said brakes work much better, he reminded me my truck is 24 years old

Christ...thank you.

My 95 3500 has only had 1 set of new rear shoes in 225K miles. numerous sets of fronts. I went to the larger Chevy wheel cylinders last year. They helped. But the factory proportioning is set way safe. With larger loads it could use way more rear bias. Mine carries a 1500lb camper, 6500 triaxle trailer and 3100lb car, plus tools, scooter, generator, etc. Probably north of 19,000lbs. My next swap is to run a bypass in the rear line direct from the master cylinder.

do those trucks have a load bias block [for lack of a better term] in the rear brake line[s] like my caravan has ?
if so, would removing this block improve the brake feel, or would it provide too much rear braking ?

Your star wheel is most likely seized. It should turn freely on both sides, if not, remove it and clean it up, put anti-seize on the threads and the opposite thimble to get it working again. I've found many of them locked up.