Swapped Dually axles to SRW axle, now back brakes skid almost every stop sign

[Rumble]

i have a 1987 crew cab, 4x4 , it was a dually, i changed it to lighter duty 8 lug in front and a 14 bolt FF in back, i got rid of the overload brake thing, i wont be towing anything heavy,

i was told that the lever adds more braking pressure to the rear when the truck is loaded down,

anyway, i am not sure what to do, do i need a different proportioning valve?

I just want it to brake normal, years ago i knew someone that had the same problem when they converted to a SRW axle

i appreciate any info