Anonymous Waffle Posted April 29, 2017 Report Share Posted April 29, 2017 I've been reading up on doing 720 leaf springs on a 620, and I read some info that different trucks had different # of leafs in a pack. My long bed truck has 4 main leafs and a large overload leaf, similar to a 521's leaf pack. Vs pictures I've seen of 2 main springs and a overload. I'm aware my truck used to be a farm truck, could the p.o. possibly have changed out the springs, or are long bed 620's rated for more weight, thus having more leafs? 1 Quote Link to comment
datzenmike Posted April 29, 2017 Report Share Posted April 29, 2017 The '73 had (standard cab short wheelbase 2 X 0.28" thick 1 X 0.24" 2 X 0.51" ....The '73 spring constant was 145 to 650 pounds per inch The '78 KC had Standard cab long wheelbase 2 X 0.28" 1 X 0.51" .... the '78 spring constant is 106 to 308 lb/in. Some 520s were rated to carry over a ton on their springs. Rather than change to lighter springs for a lighter payload on the later 521/620, they just kept them and lowered the rating on paper. This is just an opinion. At some point the springs were reduced for a better ride. 1 Quote Link to comment
red13 Posted April 30, 2017 Report Share Posted April 30, 2017 I have d21 leafs on mine Apprently 1 Quote Link to comment
fastdadd Posted May 1, 2017 Report Share Posted May 1, 2017 720 4x4 springs will be lower than 620..d21 will go even lower but the center alignment pin are in different locations i have 720 4x4 with the over loads from 620 put on top of the main leafs to flatten the even more i think i ended up with a three inch drop 1 Quote Link to comment
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