I have a Traxxas Slash with rear big bore shocks and progressive rate springs. The rear end had been sagging a lot, and would bottom out easily. I tried to fix it by filling them up with 37.5 weight oil, but it only helped a little bit. Are there any stiffer springs I can buy?

hmmmm i would say look into harder springs, i run 45wt on my stampede with stocks springs and i sag but very minimal

try 50wt shock oil, it works for me

i use 60wt oil in the back of my slash with the stock shocks and springs and that works pretty good, i would try 50 or 60wt and see how that works

i had the same issue with mine but i had the etock shocks what i did was rebuild them and used stock springs and 70 wt. oil and i haven't had an issue yet (knock on wood).

Yeah when these shocks explod or when i notice some performance loss, i'll be switching the back to higher weight oil 60wt i think

my rear big bores leak like no tomorrow...I've tried re setting them 5 times or so...

fronts are fine, and my stock shocks never leaked after I messed with them...

They leak around the cap, not the bottom

briananator, try teflon tape around the threads